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stutters and back fires when throttle floored ...wrangler 4.0 mpi
I have a jeep wrangler 4.0 mpi ...with a LPG gas conversion it is becoming difficult to start and when on petrol it stutters........fine if i get it started but as soon as the thottle is floored .......back firing and stutters (me thinks fuel starvation?) on lpg its fine........... or is it a fault on the petrol side........pump ...regulator...injectors? pump works ........not pressure tested....tank cleaned out. any help.........thanks |
Re: stutters and back fires when throttle floored ...wrangler 4.0 mpi
Backfire usually means spark issues to me....
Mike 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's Mick Miller wrote: > > I have a jeep wrangler 4.0 mpi ...with a LPG gas conversion > > it is becoming difficult to start and when on petrol it > stutters........fine if i get it started but as soon as the thottle is > floored .......back firing and stutters (me thinks fuel starvation?) > > on lpg its fine........... > > or is it a fault on the petrol side........pump > ..regulator...injectors? > > pump works ........not pressure tested....tank cleaned out. > > any help.........thanks |
Re: stutters and back fires when throttle floored ...wrangler 4.0 mpi
Backfire usually means spark issues to me....
Mike 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's Mick Miller wrote: > > I have a jeep wrangler 4.0 mpi ...with a LPG gas conversion > > it is becoming difficult to start and when on petrol it > stutters........fine if i get it started but as soon as the thottle is > floored .......back firing and stutters (me thinks fuel starvation?) > > on lpg its fine........... > > or is it a fault on the petrol side........pump > ..regulator...injectors? > > pump works ........not pressure tested....tank cleaned out. > > any help.........thanks |
Re: stutters and back fires when throttle floored ...wrangler 4.0 mpi
Backfire usually means spark issues to me....
Mike 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's Mick Miller wrote: > > I have a jeep wrangler 4.0 mpi ...with a LPG gas conversion > > it is becoming difficult to start and when on petrol it > stutters........fine if i get it started but as soon as the thottle is > floored .......back firing and stutters (me thinks fuel starvation?) > > on lpg its fine........... > > or is it a fault on the petrol side........pump > ..regulator...injectors? > > pump works ........not pressure tested....tank cleaned out. > > any help.........thanks |
Re: stutters and back fires when throttle floored ...wrangler 4.0 mpi
wish it was.......it works fine on lpg so the spark side and timing is fine........feels fuel starvation >Backfire usually means spark issues to me.... > >Mike >86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 >88 Cherokee 235 BFG AT's > >Mick Miller wrote: >> >> I have a jeep wrangler 4.0 mpi ...with a LPG gas conversion >> >> it is becoming difficult to start and when on petrol it >> stutters........fine if i get it started but as soon as the thottle is >> floored .......back firing and stutters (me thinks fuel starvation?) >> >> on lpg its fine........... >> >> or is it a fault on the petrol side........pump >> ..regulator...injectors? >> >> pump works ........not pressure tested....tank cleaned out. >> >> any help.........thanks |
Re: stutters and back fires when throttle floored ...wrangler 4.0 mpi
wish it was.......it works fine on lpg so the spark side and timing is fine........feels fuel starvation >Backfire usually means spark issues to me.... > >Mike >86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 >88 Cherokee 235 BFG AT's > >Mick Miller wrote: >> >> I have a jeep wrangler 4.0 mpi ...with a LPG gas conversion >> >> it is becoming difficult to start and when on petrol it >> stutters........fine if i get it started but as soon as the thottle is >> floored .......back firing and stutters (me thinks fuel starvation?) >> >> on lpg its fine........... >> >> or is it a fault on the petrol side........pump >> ..regulator...injectors? >> >> pump works ........not pressure tested....tank cleaned out. >> >> any help.........thanks |
Re: stutters and back fires when throttle floored ...wrangler 4.0 mpi
wish it was.......it works fine on lpg so the spark side and timing is fine........feels fuel starvation >Backfire usually means spark issues to me.... > >Mike >86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 >88 Cherokee 235 BFG AT's > >Mick Miller wrote: >> >> I have a jeep wrangler 4.0 mpi ...with a LPG gas conversion >> >> it is becoming difficult to start and when on petrol it >> stutters........fine if i get it started but as soon as the thottle is >> floored .......back firing and stutters (me thinks fuel starvation?) >> >> on lpg its fine........... >> >> or is it a fault on the petrol side........pump >> ..regulator...injectors? >> >> pump works ........not pressure tested....tank cleaned out. >> >> any help.........thanks |
Re: stutters and back fires when throttle floored ...wrangler 4.0 mpi
Do you live anywhere where it is cold enough to cause condensation to
freeze up? I note the use of the word petrol, but just around freezing temps and non or low use of the gas with less than a full tank in it can cause a lot of condensation in the gas tank. This can plug up the pickup sock/filter in the tank with ice beads. Maybe try some gas line antifreeze? Mike Mick Miller wrote: > > wish it was.......it works fine on lpg so the spark side and timing is > fine........feels fuel starvation > > >Backfire usually means spark issues to me.... > > > >Mike > >86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 > >88 Cherokee 235 BFG AT's > > > >Mick Miller wrote: > >> > >> I have a jeep wrangler 4.0 mpi ...with a LPG gas conversion > >> > >> it is becoming difficult to start and when on petrol it > >> stutters........fine if i get it started but as soon as the thottle is > >> floored .......back firing and stutters (me thinks fuel starvation?) > >> > >> on lpg its fine........... > >> > >> or is it a fault on the petrol side........pump > >> ..regulator...injectors? > >> > >> pump works ........not pressure tested....tank cleaned out. > >> > >> any help.........thanks |
Re: stutters and back fires when throttle floored ...wrangler 4.0 mpi
Do you live anywhere where it is cold enough to cause condensation to
freeze up? I note the use of the word petrol, but just around freezing temps and non or low use of the gas with less than a full tank in it can cause a lot of condensation in the gas tank. This can plug up the pickup sock/filter in the tank with ice beads. Maybe try some gas line antifreeze? Mike Mick Miller wrote: > > wish it was.......it works fine on lpg so the spark side and timing is > fine........feels fuel starvation > > >Backfire usually means spark issues to me.... > > > >Mike > >86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 > >88 Cherokee 235 BFG AT's > > > >Mick Miller wrote: > >> > >> I have a jeep wrangler 4.0 mpi ...with a LPG gas conversion > >> > >> it is becoming difficult to start and when on petrol it > >> stutters........fine if i get it started but as soon as the thottle is > >> floored .......back firing and stutters (me thinks fuel starvation?) > >> > >> on lpg its fine........... > >> > >> or is it a fault on the petrol side........pump > >> ..regulator...injectors? > >> > >> pump works ........not pressure tested....tank cleaned out. > >> > >> any help.........thanks |
Re: stutters and back fires when throttle floored ...wrangler 4.0 mpi
Do you live anywhere where it is cold enough to cause condensation to
freeze up? I note the use of the word petrol, but just around freezing temps and non or low use of the gas with less than a full tank in it can cause a lot of condensation in the gas tank. This can plug up the pickup sock/filter in the tank with ice beads. Maybe try some gas line antifreeze? Mike Mick Miller wrote: > > wish it was.......it works fine on lpg so the spark side and timing is > fine........feels fuel starvation > > >Backfire usually means spark issues to me.... > > > >Mike > >86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 > >88 Cherokee 235 BFG AT's > > > >Mick Miller wrote: > >> > >> I have a jeep wrangler 4.0 mpi ...with a LPG gas conversion > >> > >> it is becoming difficult to start and when on petrol it > >> stutters........fine if i get it started but as soon as the thottle is > >> floored .......back firing and stutters (me thinks fuel starvation?) > >> > >> on lpg its fine........... > >> > >> or is it a fault on the petrol side........pump > >> ..regulator...injectors? > >> > >> pump works ........not pressure tested....tank cleaned out. > >> > >> any help.........thanks |
Re: stutters and back fires when throttle floored ...wrangler 4.0 mpi
na.....no freezing >Do you live anywhere where it is cold enough to cause condensation to >freeze up? > >I note the use of the word petrol, but just around freezing temps and >non or low use of the gas with less than a full tank in it can cause a >lot of condensation in the gas tank. This can plug up the pickup >sock/filter in the tank with ice beads. > >Maybe try some gas line antifreeze? > >Mike > >Mick Miller wrote: >> >> wish it was.......it works fine on lpg so the spark side and timing is >> fine........feels fuel starvation >> >> >Backfire usually means spark issues to me.... >> > >> >Mike >> >86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 >> >88 Cherokee 235 BFG AT's >> > >> >Mick Miller wrote: >> >> >> >> I have a jeep wrangler 4.0 mpi ...with a LPG gas conversion >> >> >> >> it is becoming difficult to start and when on petrol it >> >> stutters........fine if i get it started but as soon as the thottle is >> >> floored .......back firing and stutters (me thinks fuel starvation?) >> >> >> >> on lpg its fine........... >> >> >> >> or is it a fault on the petrol side........pump >> >> ..regulator...injectors? >> >> >> >> pump works ........not pressure tested....tank cleaned out. >> >> >> >> any help.........thanks |
Re: stutters and back fires when throttle floored ...wrangler 4.0 mpi
na.....no freezing >Do you live anywhere where it is cold enough to cause condensation to >freeze up? > >I note the use of the word petrol, but just around freezing temps and >non or low use of the gas with less than a full tank in it can cause a >lot of condensation in the gas tank. This can plug up the pickup >sock/filter in the tank with ice beads. > >Maybe try some gas line antifreeze? > >Mike > >Mick Miller wrote: >> >> wish it was.......it works fine on lpg so the spark side and timing is >> fine........feels fuel starvation >> >> >Backfire usually means spark issues to me.... >> > >> >Mike >> >86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 >> >88 Cherokee 235 BFG AT's >> > >> >Mick Miller wrote: >> >> >> >> I have a jeep wrangler 4.0 mpi ...with a LPG gas conversion >> >> >> >> it is becoming difficult to start and when on petrol it >> >> stutters........fine if i get it started but as soon as the thottle is >> >> floored .......back firing and stutters (me thinks fuel starvation?) >> >> >> >> on lpg its fine........... >> >> >> >> or is it a fault on the petrol side........pump >> >> ..regulator...injectors? >> >> >> >> pump works ........not pressure tested....tank cleaned out. >> >> >> >> any help.........thanks |
Re: stutters and back fires when throttle floored ...wrangler 4.0 mpi
na.....no freezing >Do you live anywhere where it is cold enough to cause condensation to >freeze up? > >I note the use of the word petrol, but just around freezing temps and >non or low use of the gas with less than a full tank in it can cause a >lot of condensation in the gas tank. This can plug up the pickup >sock/filter in the tank with ice beads. > >Maybe try some gas line antifreeze? > >Mike > >Mick Miller wrote: >> >> wish it was.......it works fine on lpg so the spark side and timing is >> fine........feels fuel starvation >> >> >Backfire usually means spark issues to me.... >> > >> >Mike >> >86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 >> >88 Cherokee 235 BFG AT's >> > >> >Mick Miller wrote: >> >> >> >> I have a jeep wrangler 4.0 mpi ...with a LPG gas conversion >> >> >> >> it is becoming difficult to start and when on petrol it >> >> stutters........fine if i get it started but as soon as the thottle is >> >> floored .......back firing and stutters (me thinks fuel starvation?) >> >> >> >> on lpg its fine........... >> >> >> >> or is it a fault on the petrol side........pump >> >> ..regulator...injectors? >> >> >> >> pump works ........not pressure tested....tank cleaned out. >> >> >> >> any help.........thanks |
Re: stutters and back fires when throttle floored ...wrangler 4.0 mpi
Back fires are unburned gasoline. And most likely a bad spark plug
like Mike has said. I could be burnt valves seeing you use LPG, probably without the hard seat conversion. God Bless America, ßill O|||||||O mailto:-------------------- http://www.----------.com/ Mick Miller wrote: > > wish it was.......it works fine on lpg so the spark side and timing is > fine........feels fuel starvation > > >Backfire usually means spark issues to me.... > > > >Mike > >86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 > >88 Cherokee 235 BFG AT's |
Re: stutters and back fires when throttle floored ...wrangler 4.0 mpi
Back fires are unburned gasoline. And most likely a bad spark plug
like Mike has said. I could be burnt valves seeing you use LPG, probably without the hard seat conversion. God Bless America, ßill O|||||||O mailto:-------------------- http://www.----------.com/ Mick Miller wrote: > > wish it was.......it works fine on lpg so the spark side and timing is > fine........feels fuel starvation > > >Backfire usually means spark issues to me.... > > > >Mike > >86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 > >88 Cherokee 235 BFG AT's |
Re: stutters and back fires when throttle floored ...wrangler 4.0 mpi
Back fires are unburned gasoline. And most likely a bad spark plug
like Mike has said. I could be burnt valves seeing you use LPG, probably without the hard seat conversion. God Bless America, ßill O|||||||O mailto:-------------------- http://www.----------.com/ Mick Miller wrote: > > wish it was.......it works fine on lpg so the spark side and timing is > fine........feels fuel starvation > > >Backfire usually means spark issues to me.... > > > >Mike > >86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 > >88 Cherokee 235 BFG AT's |
Re: stutters and back fires when throttle floored ...wrangler 4.0 mpi
but lpg works fine ........no backfire > Back fires are unburned gasoline. And most likely a bad spark plug >like Mike has said. I could be burnt valves seeing you use LPG, probably >without the hard seat conversion. > God Bless America, ßill O|||||||O >mailto:-------------------- http://www.----------.com/ > >Mick Miller wrote: >> >> wish it was.......it works fine on lpg so the spark side and timing is >> fine........feels fuel starvation >> >> >Backfire usually means spark issues to me.... >> > >> >Mike >> >86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 >> >88 Cherokee 235 BFG AT's |
Re: stutters and back fires when throttle floored ...wrangler 4.0 mpi
but lpg works fine ........no backfire > Back fires are unburned gasoline. And most likely a bad spark plug >like Mike has said. I could be burnt valves seeing you use LPG, probably >without the hard seat conversion. > God Bless America, ßill O|||||||O >mailto:-------------------- http://www.----------.com/ > >Mick Miller wrote: >> >> wish it was.......it works fine on lpg so the spark side and timing is >> fine........feels fuel starvation >> >> >Backfire usually means spark issues to me.... >> > >> >Mike >> >86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 >> >88 Cherokee 235 BFG AT's |
Re: stutters and back fires when throttle floored ...wrangler 4.0 mpi
but lpg works fine ........no backfire > Back fires are unburned gasoline. And most likely a bad spark plug >like Mike has said. I could be burnt valves seeing you use LPG, probably >without the hard seat conversion. > God Bless America, ßill O|||||||O >mailto:-------------------- http://www.----------.com/ > >Mick Miller wrote: >> >> wish it was.......it works fine on lpg so the spark side and timing is >> fine........feels fuel starvation >> >> >Backfire usually means spark issues to me.... >> > >> >Mike >> >86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 >> >88 Cherokee 235 BFG AT's |
Re: stutters and back fires when throttle floored ...wrangler 4.0 mpi
Not at that temperature.
God Bless America, ßill O|||||||O mailto:-------------------- http://www.----------.com/ Mick Miller wrote: > > but lpg works fine ........no backfire |
Re: stutters and back fires when throttle floored ...wrangler 4.0 mpi
Not at that temperature.
God Bless America, ßill O|||||||O mailto:-------------------- http://www.----------.com/ Mick Miller wrote: > > but lpg works fine ........no backfire |
Re: stutters and back fires when throttle floored ...wrangler 4.0 mpi
Not at that temperature.
God Bless America, ßill O|||||||O mailto:-------------------- http://www.----------.com/ Mick Miller wrote: > > but lpg works fine ........no backfire |
Re: stutters and back fires when throttle floored ...wrangler 4.0 mpi
Wouldn't lpg & gasoline require different conditions to run well? My bet is
that whatever setup you have (plugs, coil, etc.) would be optimized for one or the other, leaving the 2nd running a bit worse. Just my $.02. "Mick Miller" <061268@hotmail.com> wrote in message news:403835a0.134533@news.freeserve.com... > > > but lpg works fine ........no backfire > > > Back fires are unburned gasoline. And most likely a bad spark plug > >like Mike has said. I could be burnt valves seeing you use LPG, probably > >without the hard seat conversion. > > God Bless America, ßill O|||||||O > >mailto:-------------------- http://www.----------.com/ > > > >Mick Miller wrote: > >> > >> wish it was.......it works fine on lpg so the spark side and timing is > >> fine........feels fuel starvation > >> > >> >Backfire usually means spark issues to me.... > >> > > >> >Mike > >> >86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 > >> >88 Cherokee 235 BFG AT's > |
Re: stutters and back fires when throttle floored ...wrangler 4.0 mpi
Wouldn't lpg & gasoline require different conditions to run well? My bet is
that whatever setup you have (plugs, coil, etc.) would be optimized for one or the other, leaving the 2nd running a bit worse. Just my $.02. "Mick Miller" <061268@hotmail.com> wrote in message news:403835a0.134533@news.freeserve.com... > > > but lpg works fine ........no backfire > > > Back fires are unburned gasoline. And most likely a bad spark plug > >like Mike has said. I could be burnt valves seeing you use LPG, probably > >without the hard seat conversion. > > God Bless America, ßill O|||||||O > >mailto:-------------------- http://www.----------.com/ > > > >Mick Miller wrote: > >> > >> wish it was.......it works fine on lpg so the spark side and timing is > >> fine........feels fuel starvation > >> > >> >Backfire usually means spark issues to me.... > >> > > >> >Mike > >> >86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 > >> >88 Cherokee 235 BFG AT's > |
Re: stutters and back fires when throttle floored ...wrangler 4.0 mpi
Wouldn't lpg & gasoline require different conditions to run well? My bet is
that whatever setup you have (plugs, coil, etc.) would be optimized for one or the other, leaving the 2nd running a bit worse. Just my $.02. "Mick Miller" <061268@hotmail.com> wrote in message news:403835a0.134533@news.freeserve.com... > > > but lpg works fine ........no backfire > > > Back fires are unburned gasoline. And most likely a bad spark plug > >like Mike has said. I could be burnt valves seeing you use LPG, probably > >without the hard seat conversion. > > God Bless America, ßill O|||||||O > >mailto:-------------------- http://www.----------.com/ > > > >Mick Miller wrote: > >> > >> wish it was.......it works fine on lpg so the spark side and timing is > >> fine........feels fuel starvation > >> > >> >Backfire usually means spark issues to me.... > >> > > >> >Mike > >> >86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 > >> >88 Cherokee 235 BFG AT's > |
Re: stutters and back fires when throttle floored ...wrangler 4.0 mpi
I wrestled with a similar problem after installing a supercharger on my 4.0.
Turns out the fuel pump was only puttting out about 30psi instead of the 45-50 it should. You can easily test the fuel line pressure at the shrader valve fitting on the fuel rail. |
Re: stutters and back fires when throttle floored ...wrangler 4.0 mpi
I wrestled with a similar problem after installing a supercharger on my 4.0.
Turns out the fuel pump was only puttting out about 30psi instead of the 45-50 it should. You can easily test the fuel line pressure at the shrader valve fitting on the fuel rail. |
Re: stutters and back fires when throttle floored ...wrangler 4.0 mpi
I wrestled with a similar problem after installing a supercharger on my 4.0.
Turns out the fuel pump was only puttting out about 30psi instead of the 45-50 it should. You can easily test the fuel line pressure at the shrader valve fitting on the fuel rail. |
Re: stutters and back fires when throttle floored ...wrangler 4.0 mpi
On 22 Feb 2004 16:39:54 GMT, dalewhite@aol.com (Dalewhite) wrote:
thats what i think it is.................but not checked the pressure yet what i am getting it when floored.........revs pick up then stutter!!.....and back fire gradual throttle much less of a problem did.....reset the ecu .....by disconecting the battery .......and that sort of cleared it but its still there >I wrestled with a similar problem after installing a supercharger on my 4.0. >Turns out the fuel pump was only puttting out about 30psi instead of the 45-50 >it should. You can easily test the fuel line pressure at the shrader valve >fitting on the fuel rail. |
Re: stutters and back fires when throttle floored ...wrangler 4.0 mpi
On 22 Feb 2004 16:39:54 GMT, dalewhite@aol.com (Dalewhite) wrote:
thats what i think it is.................but not checked the pressure yet what i am getting it when floored.........revs pick up then stutter!!.....and back fire gradual throttle much less of a problem did.....reset the ecu .....by disconecting the battery .......and that sort of cleared it but its still there >I wrestled with a similar problem after installing a supercharger on my 4.0. >Turns out the fuel pump was only puttting out about 30psi instead of the 45-50 >it should. You can easily test the fuel line pressure at the shrader valve >fitting on the fuel rail. |
Re: stutters and back fires when throttle floored ...wrangler 4.0 mpi
On 22 Feb 2004 16:39:54 GMT, dalewhite@aol.com (Dalewhite) wrote:
thats what i think it is.................but not checked the pressure yet what i am getting it when floored.........revs pick up then stutter!!.....and back fire gradual throttle much less of a problem did.....reset the ecu .....by disconecting the battery .......and that sort of cleared it but its still there >I wrestled with a similar problem after installing a supercharger on my 4.0. >Turns out the fuel pump was only puttting out about 30psi instead of the 45-50 >it should. You can easily test the fuel line pressure at the shrader valve >fitting on the fuel rail. |
Re: stutters and back fires when throttle floored ...wrangler 4.0 mpi
Mick Miller did pass the time by typing:
> On 22 Feb 2004 16:39:54 GMT, dalewhite@aol.com (Dalewhite) wrote: > > > thats what i think it is.................but not checked the pressure > yet > > what i am getting it when floored.........revs pick up then > stutter!!.....and back fire > > gradual throttle much less of a problem What that tells me is you have a problem with WOT mode (Wide Open Throttle) That puts some sensors back in the loop, chief among them is the MAP sensor and MAT sensor. http://members.cox.net/wilsond/Fixes/diagnostics.html will give you an idea. Throw an ohmmeter across the MAT sensor, it should give a value corresponding to the chart. http://members.cox.net/wilsond/Fixes...tml#tempmatrix (Give or take. That table isn't always accurate for all years) (as long as it's not zero or infinite your fine) Then check the MAP sensor. Center pin should be 4-5 volts with ignition on, engine not running. Next, your TPS (throttle position sensor). Ignition on, engine not running. Backprobe (don't disconnect, use a pin) the TPS center wire and measure voltage to ground. With the throttle plate at rest you should see >200mv. Rotate the plate to full open and you should see <4.8V. Now your O2 sensor. ignition off. Disconnect the harness by the oil pan and measure the resistance across the two white wires. You should get 5 to 7 Ohms on a "you can put your hand on it" exhaust pipe (infinite is bad) Now the injectors. Disconnect the feed and measure the resistance across each one. You should get 14-15 Ohms +- 2 Ohms (short and high resistance is bad) (although this is more for a rough idle than detonation) Next.. (yep, next) Check the vac line that feeds your evap canister. (on the I6 it's the forward connection on the intake rail) (if you have a vac bleader this is a good thing).. if not your going to disconnect the line that feeds the evap canister vac/switch and suck on it. You should hear a click. If all you get is a mouthfull of gas fumes that valve in the canister is shot. (more for rough idle/rich burn) I'm out of both coffee and ideas for now. Must go make another pot. :) -- -- DougW -- 93 ZJ 4.0 http://members.cox.net/wilsond HESCO Supercharger - 300W IASCA Stereo - Edelbrock IAS Shocks Gibson Exhaust - rear DCpower - custom gauge install - Stillen Rotors |
Re: stutters and back fires when throttle floored ...wrangler 4.0 mpi
Mick Miller did pass the time by typing:
> On 22 Feb 2004 16:39:54 GMT, dalewhite@aol.com (Dalewhite) wrote: > > > thats what i think it is.................but not checked the pressure > yet > > what i am getting it when floored.........revs pick up then > stutter!!.....and back fire > > gradual throttle much less of a problem What that tells me is you have a problem with WOT mode (Wide Open Throttle) That puts some sensors back in the loop, chief among them is the MAP sensor and MAT sensor. http://members.cox.net/wilsond/Fixes/diagnostics.html will give you an idea. Throw an ohmmeter across the MAT sensor, it should give a value corresponding to the chart. http://members.cox.net/wilsond/Fixes...tml#tempmatrix (Give or take. That table isn't always accurate for all years) (as long as it's not zero or infinite your fine) Then check the MAP sensor. Center pin should be 4-5 volts with ignition on, engine not running. Next, your TPS (throttle position sensor). Ignition on, engine not running. Backprobe (don't disconnect, use a pin) the TPS center wire and measure voltage to ground. With the throttle plate at rest you should see >200mv. Rotate the plate to full open and you should see <4.8V. Now your O2 sensor. ignition off. Disconnect the harness by the oil pan and measure the resistance across the two white wires. You should get 5 to 7 Ohms on a "you can put your hand on it" exhaust pipe (infinite is bad) Now the injectors. Disconnect the feed and measure the resistance across each one. You should get 14-15 Ohms +- 2 Ohms (short and high resistance is bad) (although this is more for a rough idle than detonation) Next.. (yep, next) Check the vac line that feeds your evap canister. (on the I6 it's the forward connection on the intake rail) (if you have a vac bleader this is a good thing).. if not your going to disconnect the line that feeds the evap canister vac/switch and suck on it. You should hear a click. If all you get is a mouthfull of gas fumes that valve in the canister is shot. (more for rough idle/rich burn) I'm out of both coffee and ideas for now. Must go make another pot. :) -- -- DougW -- 93 ZJ 4.0 http://members.cox.net/wilsond HESCO Supercharger - 300W IASCA Stereo - Edelbrock IAS Shocks Gibson Exhaust - rear DCpower - custom gauge install - Stillen Rotors |
Re: stutters and back fires when throttle floored ...wrangler 4.0 mpi
Mick Miller did pass the time by typing:
> On 22 Feb 2004 16:39:54 GMT, dalewhite@aol.com (Dalewhite) wrote: > > > thats what i think it is.................but not checked the pressure > yet > > what i am getting it when floored.........revs pick up then > stutter!!.....and back fire > > gradual throttle much less of a problem What that tells me is you have a problem with WOT mode (Wide Open Throttle) That puts some sensors back in the loop, chief among them is the MAP sensor and MAT sensor. http://members.cox.net/wilsond/Fixes/diagnostics.html will give you an idea. Throw an ohmmeter across the MAT sensor, it should give a value corresponding to the chart. http://members.cox.net/wilsond/Fixes...tml#tempmatrix (Give or take. That table isn't always accurate for all years) (as long as it's not zero or infinite your fine) Then check the MAP sensor. Center pin should be 4-5 volts with ignition on, engine not running. Next, your TPS (throttle position sensor). Ignition on, engine not running. Backprobe (don't disconnect, use a pin) the TPS center wire and measure voltage to ground. With the throttle plate at rest you should see >200mv. Rotate the plate to full open and you should see <4.8V. Now your O2 sensor. ignition off. Disconnect the harness by the oil pan and measure the resistance across the two white wires. You should get 5 to 7 Ohms on a "you can put your hand on it" exhaust pipe (infinite is bad) Now the injectors. Disconnect the feed and measure the resistance across each one. You should get 14-15 Ohms +- 2 Ohms (short and high resistance is bad) (although this is more for a rough idle than detonation) Next.. (yep, next) Check the vac line that feeds your evap canister. (on the I6 it's the forward connection on the intake rail) (if you have a vac bleader this is a good thing).. if not your going to disconnect the line that feeds the evap canister vac/switch and suck on it. You should hear a click. If all you get is a mouthfull of gas fumes that valve in the canister is shot. (more for rough idle/rich burn) I'm out of both coffee and ideas for now. Must go make another pot. :) -- -- DougW -- 93 ZJ 4.0 http://members.cox.net/wilsond HESCO Supercharger - 300W IASCA Stereo - Edelbrock IAS Shocks Gibson Exhaust - rear DCpower - custom gauge install - Stillen Rotors |
Re: stutters and back fires when throttle floored ...wrangler 4.0 mpi
I still think condensation could be an issue.
Maybe try some gas line antifreeze anyway, can't hurt. The antifreeze mixes with the water allowing it to burn through. Water getting into injectors can cause strange things to happen. Mike Mick Miller wrote: > > na.....no freezing > > >Do you live anywhere where it is cold enough to cause condensation to > >freeze up? > > > >I note the use of the word petrol, but just around freezing temps and > >non or low use of the gas with less than a full tank in it can cause a > >lot of condensation in the gas tank. This can plug up the pickup > >sock/filter in the tank with ice beads. > > > >Maybe try some gas line antifreeze? > > > >Mike > > > >Mick Miller wrote: > >> > >> wish it was.......it works fine on lpg so the spark side and timing is > >> fine........feels fuel starvation > >> > >> >Backfire usually means spark issues to me.... > >> > > >> >Mike > >> >86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 > >> >88 Cherokee 235 BFG AT's > >> > > >> >Mick Miller wrote: > >> >> > >> >> I have a jeep wrangler 4.0 mpi ...with a LPG gas conversion > >> >> > >> >> it is becoming difficult to start and when on petrol it > >> >> stutters........fine if i get it started but as soon as the thottle is > >> >> floored .......back firing and stutters (me thinks fuel starvation?) > >> >> > >> >> on lpg its fine........... > >> >> > >> >> or is it a fault on the petrol side........pump > >> >> ..regulator...injectors? > >> >> > >> >> pump works ........not pressure tested....tank cleaned out. > >> >> > >> >> any help.........thanks |
Re: stutters and back fires when throttle floored ...wrangler 4.0 mpi
I still think condensation could be an issue.
Maybe try some gas line antifreeze anyway, can't hurt. The antifreeze mixes with the water allowing it to burn through. Water getting into injectors can cause strange things to happen. Mike Mick Miller wrote: > > na.....no freezing > > >Do you live anywhere where it is cold enough to cause condensation to > >freeze up? > > > >I note the use of the word petrol, but just around freezing temps and > >non or low use of the gas with less than a full tank in it can cause a > >lot of condensation in the gas tank. This can plug up the pickup > >sock/filter in the tank with ice beads. > > > >Maybe try some gas line antifreeze? > > > >Mike > > > >Mick Miller wrote: > >> > >> wish it was.......it works fine on lpg so the spark side and timing is > >> fine........feels fuel starvation > >> > >> >Backfire usually means spark issues to me.... > >> > > >> >Mike > >> >86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 > >> >88 Cherokee 235 BFG AT's > >> > > >> >Mick Miller wrote: > >> >> > >> >> I have a jeep wrangler 4.0 mpi ...with a LPG gas conversion > >> >> > >> >> it is becoming difficult to start and when on petrol it > >> >> stutters........fine if i get it started but as soon as the thottle is > >> >> floored .......back firing and stutters (me thinks fuel starvation?) > >> >> > >> >> on lpg its fine........... > >> >> > >> >> or is it a fault on the petrol side........pump > >> >> ..regulator...injectors? > >> >> > >> >> pump works ........not pressure tested....tank cleaned out. > >> >> > >> >> any help.........thanks |
Re: stutters and back fires when throttle floored ...wrangler 4.0 mpi
I still think condensation could be an issue.
Maybe try some gas line antifreeze anyway, can't hurt. The antifreeze mixes with the water allowing it to burn through. Water getting into injectors can cause strange things to happen. Mike Mick Miller wrote: > > na.....no freezing > > >Do you live anywhere where it is cold enough to cause condensation to > >freeze up? > > > >I note the use of the word petrol, but just around freezing temps and > >non or low use of the gas with less than a full tank in it can cause a > >lot of condensation in the gas tank. This can plug up the pickup > >sock/filter in the tank with ice beads. > > > >Maybe try some gas line antifreeze? > > > >Mike > > > >Mick Miller wrote: > >> > >> wish it was.......it works fine on lpg so the spark side and timing is > >> fine........feels fuel starvation > >> > >> >Backfire usually means spark issues to me.... > >> > > >> >Mike > >> >86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 > >> >88 Cherokee 235 BFG AT's > >> > > >> >Mick Miller wrote: > >> >> > >> >> I have a jeep wrangler 4.0 mpi ...with a LPG gas conversion > >> >> > >> >> it is becoming difficult to start and when on petrol it > >> >> stutters........fine if i get it started but as soon as the thottle is > >> >> floored .......back firing and stutters (me thinks fuel starvation?) > >> >> > >> >> on lpg its fine........... > >> >> > >> >> or is it a fault on the petrol side........pump > >> >> ..regulator...injectors? > >> >> > >> >> pump works ........not pressure tested....tank cleaned out. > >> >> > >> >> any help.........thanks |
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