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Failed emissions test
1988 Jeep Cherokee 4.0
Failed the emissions test (grr). The NO PPM was at 1984, max. is 1126. Any ideas what the problem might be? I changed the plugs, ran some "guaranteed to pass" through it, cleaned the air filter, and did the test with the car well warmed up. The guy said if I ran it cold it might pass, as the NO ppm is caused by a cylinder running too hot. Any insight would be great, I'm currently car-less! Regards, Chris |
Re: Failed emissions test
Our 88 failed too and they figured the EGR solenoid had failed and
changed it. Plugs, cap and wires got changed too. Same deal another fail, so by this time I had enough money in it to get a 2 year conditional as it was the first test when the computer wouldn't give the conditional! My 88 4.0 was under recall for a bad O2 sensor. Free new O2 sensor and it passed the test. Got my money back from the other tests too, because I took it to a Jeep dealer for the test just to avoid silly things and they were too lazy to check. It would be worth calling Chrysler and asking about recalls using your VIN. My recall doesn't show up in the on line databases. Carbon build up can also make it run hot, the carbon gets cherry and spark knock can happen. Any knocking under load? Mike 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's Christian Fry wrote: > > 1988 Jeep Cherokee 4.0 > > Failed the emissions test (grr). The NO PPM was at 1984, max. is 1126. Any > ideas what the problem might be? I changed the plugs, ran some "guaranteed > to pass" through it, cleaned the air filter, and did the test with the car > well warmed up. The guy said if I ran it cold it might pass, as the NO ppm > is caused by a cylinder running too hot. Any insight would be great, I'm > currently car-less! > > Regards, > Chris |
Re: Failed emissions test
Our 88 failed too and they figured the EGR solenoid had failed and
changed it. Plugs, cap and wires got changed too. Same deal another fail, so by this time I had enough money in it to get a 2 year conditional as it was the first test when the computer wouldn't give the conditional! My 88 4.0 was under recall for a bad O2 sensor. Free new O2 sensor and it passed the test. Got my money back from the other tests too, because I took it to a Jeep dealer for the test just to avoid silly things and they were too lazy to check. It would be worth calling Chrysler and asking about recalls using your VIN. My recall doesn't show up in the on line databases. Carbon build up can also make it run hot, the carbon gets cherry and spark knock can happen. Any knocking under load? Mike 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's Christian Fry wrote: > > 1988 Jeep Cherokee 4.0 > > Failed the emissions test (grr). The NO PPM was at 1984, max. is 1126. Any > ideas what the problem might be? I changed the plugs, ran some "guaranteed > to pass" through it, cleaned the air filter, and did the test with the car > well warmed up. The guy said if I ran it cold it might pass, as the NO ppm > is caused by a cylinder running too hot. Any insight would be great, I'm > currently car-less! > > Regards, > Chris |
Re: Failed emissions test
Our 88 failed too and they figured the EGR solenoid had failed and
changed it. Plugs, cap and wires got changed too. Same deal another fail, so by this time I had enough money in it to get a 2 year conditional as it was the first test when the computer wouldn't give the conditional! My 88 4.0 was under recall for a bad O2 sensor. Free new O2 sensor and it passed the test. Got my money back from the other tests too, because I took it to a Jeep dealer for the test just to avoid silly things and they were too lazy to check. It would be worth calling Chrysler and asking about recalls using your VIN. My recall doesn't show up in the on line databases. Carbon build up can also make it run hot, the carbon gets cherry and spark knock can happen. Any knocking under load? Mike 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's Christian Fry wrote: > > 1988 Jeep Cherokee 4.0 > > Failed the emissions test (grr). The NO PPM was at 1984, max. is 1126. Any > ideas what the problem might be? I changed the plugs, ran some "guaranteed > to pass" through it, cleaned the air filter, and did the test with the car > well warmed up. The guy said if I ran it cold it might pass, as the NO ppm > is caused by a cylinder running too hot. Any insight would be great, I'm > currently car-less! > > Regards, > Chris |
Re: Failed emissions test
Hi Chris,
I've never heard that before, we want it run as hot as possible to fully burn all the gases, that's why all SMOG motors run a 195 degree thermostats. Someone in this group said their Cherokee was originally bought in Europe, if that's true you may not have a catalytic converter, that's it's job to convert nitrogen oxides and hydrocarbons into harmless water. My Bronco old with three hundred thousand miles on it and never had the heads off: http://www.----------.com/smog.jpg God Bless America, ßill O|||||||O mailto:-------------------- Christian Fry wrote: > > 1988 Jeep Cherokee 4.0 > > Failed the emissions test (grr). The NO PPM was at 1984, max. is 1126. Any > ideas what the problem might be? I changed the plugs, ran some "guaranteed > to pass" through it, cleaned the air filter, and did the test with the car > well warmed up. The guy said if I ran it cold it might pass, as the NO ppm > is caused by a cylinder running too hot. Any insight would be great, I'm > currently car-less! > > Regards, > Chris |
Re: Failed emissions test
Hi Chris,
I've never heard that before, we want it run as hot as possible to fully burn all the gases, that's why all SMOG motors run a 195 degree thermostats. Someone in this group said their Cherokee was originally bought in Europe, if that's true you may not have a catalytic converter, that's it's job to convert nitrogen oxides and hydrocarbons into harmless water. My Bronco old with three hundred thousand miles on it and never had the heads off: http://www.----------.com/smog.jpg God Bless America, ßill O|||||||O mailto:-------------------- Christian Fry wrote: > > 1988 Jeep Cherokee 4.0 > > Failed the emissions test (grr). The NO PPM was at 1984, max. is 1126. Any > ideas what the problem might be? I changed the plugs, ran some "guaranteed > to pass" through it, cleaned the air filter, and did the test with the car > well warmed up. The guy said if I ran it cold it might pass, as the NO ppm > is caused by a cylinder running too hot. Any insight would be great, I'm > currently car-less! > > Regards, > Chris |
Re: Failed emissions test
Hi Chris,
I've never heard that before, we want it run as hot as possible to fully burn all the gases, that's why all SMOG motors run a 195 degree thermostats. Someone in this group said their Cherokee was originally bought in Europe, if that's true you may not have a catalytic converter, that's it's job to convert nitrogen oxides and hydrocarbons into harmless water. My Bronco old with three hundred thousand miles on it and never had the heads off: http://www.----------.com/smog.jpg God Bless America, ßill O|||||||O mailto:-------------------- Christian Fry wrote: > > 1988 Jeep Cherokee 4.0 > > Failed the emissions test (grr). The NO PPM was at 1984, max. is 1126. Any > ideas what the problem might be? I changed the plugs, ran some "guaranteed > to pass" through it, cleaned the air filter, and did the test with the car > well warmed up. The guy said if I ran it cold it might pass, as the NO ppm > is caused by a cylinder running too hot. Any insight would be great, I'm > currently car-less! > > Regards, > Chris |
Re: Failed emissions test
As usual, Romain has nailed this one. NOx is caused by high combustion
temperatures (not necessarily high coolant temp). EGR is the primary means of controlling it, so that has to work, if equipped. Timing has to be on the mark or even a little retarded. Any audible pinging is a no-no. Jerry "L.W. (ßill) ------ III" <----------@cox.net> wrote in message news:40490045.2BD1929B@cox.net... > Hi Chris, > I've never heard that before, we want it run as hot as possible to > fully burn all the gases, that's why all SMOG motors run a 195 degree > thermostats. Someone in this group said their Cherokee was originally > bought in Europe, if that's true you may not have a catalytic converter, > that's it's job to convert nitrogen oxides and hydrocarbons into > harmless water. My Bronco old with three hundred thousand miles on it > and never had the heads off: http://www.----------.com/smog.jpg > God Bless America, ßill O|||||||O > mailto:-------------------- > > Christian Fry wrote: > > > > 1988 Jeep Cherokee 4.0 > > > > Failed the emissions test (grr). The NO PPM was at 1984, max. is 1126. Any > > ideas what the problem might be? I changed the plugs, ran some "guaranteed > > to pass" through it, cleaned the air filter, and did the test with the car > > well warmed up. The guy said if I ran it cold it might pass, as the NO ppm > > is caused by a cylinder running too hot. Any insight would be great, I'm > > currently car-less! > > > > Regards, > > Chris |
Re: Failed emissions test
As usual, Romain has nailed this one. NOx is caused by high combustion
temperatures (not necessarily high coolant temp). EGR is the primary means of controlling it, so that has to work, if equipped. Timing has to be on the mark or even a little retarded. Any audible pinging is a no-no. Jerry "L.W. (ßill) ------ III" <----------@cox.net> wrote in message news:40490045.2BD1929B@cox.net... > Hi Chris, > I've never heard that before, we want it run as hot as possible to > fully burn all the gases, that's why all SMOG motors run a 195 degree > thermostats. Someone in this group said their Cherokee was originally > bought in Europe, if that's true you may not have a catalytic converter, > that's it's job to convert nitrogen oxides and hydrocarbons into > harmless water. My Bronco old with three hundred thousand miles on it > and never had the heads off: http://www.----------.com/smog.jpg > God Bless America, ßill O|||||||O > mailto:-------------------- > > Christian Fry wrote: > > > > 1988 Jeep Cherokee 4.0 > > > > Failed the emissions test (grr). The NO PPM was at 1984, max. is 1126. Any > > ideas what the problem might be? I changed the plugs, ran some "guaranteed > > to pass" through it, cleaned the air filter, and did the test with the car > > well warmed up. The guy said if I ran it cold it might pass, as the NO ppm > > is caused by a cylinder running too hot. Any insight would be great, I'm > > currently car-less! > > > > Regards, > > Chris |
Re: Failed emissions test
As usual, Romain has nailed this one. NOx is caused by high combustion
temperatures (not necessarily high coolant temp). EGR is the primary means of controlling it, so that has to work, if equipped. Timing has to be on the mark or even a little retarded. Any audible pinging is a no-no. Jerry "L.W. (ßill) ------ III" <----------@cox.net> wrote in message news:40490045.2BD1929B@cox.net... > Hi Chris, > I've never heard that before, we want it run as hot as possible to > fully burn all the gases, that's why all SMOG motors run a 195 degree > thermostats. Someone in this group said their Cherokee was originally > bought in Europe, if that's true you may not have a catalytic converter, > that's it's job to convert nitrogen oxides and hydrocarbons into > harmless water. My Bronco old with three hundred thousand miles on it > and never had the heads off: http://www.----------.com/smog.jpg > God Bless America, ßill O|||||||O > mailto:-------------------- > > Christian Fry wrote: > > > > 1988 Jeep Cherokee 4.0 > > > > Failed the emissions test (grr). The NO PPM was at 1984, max. is 1126. Any > > ideas what the problem might be? I changed the plugs, ran some "guaranteed > > to pass" through it, cleaned the air filter, and did the test with the car > > well warmed up. The guy said if I ran it cold it might pass, as the NO ppm > > is caused by a cylinder running too hot. Any insight would be great, I'm > > currently car-less! > > > > Regards, > > Chris |
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