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Re: Lost top end power in 88 Cherokee 4.0.
On May 27, 11:20 am, Mike Romain <roma...@sympatico.ca> wrote:
> Ok, I am on a fishing expedition for likely things to check. > > Our 88 Cherokee with the 4.0 has lost power above half throttle. It > goes fine up to that point, then just bogs, no matter what gear it is > in. It has been neglected for 4 years as far as tuning goes due to me > not being up to it. > > I first changed out the 'very' dirty distributor cap and rotor which > made starting 'much' faster and smoother. > > I then changed the gas filter because it was once again rusted to the > rot point after about 8 years. > > Air filter is new. > > I cleaned the connections on the TPS and IAC and verified the TPS > doesn't have any 'dead' spots with my meter. > > I cleaned the CPS and coil connections also. > > No joy on any of that. > > I have been having some cold idle issues and have been thinking on > cleaning the IAC, but don't know if that will have a top end effect or not. > > I am also thinking on unplugging the EGR just to make sure it isn't > blown vacuum wise because it only bogs under throttle when things like > the EGR are active. > > Any other ideas? > > Mike > 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 > 88 Cherokee 235 BFG AT's > Canadian Off Road Trips Photos: Non members can still view! > Jan/06http://www.imagestation.com/album/pictures.html?id=2115147590 > (More Off Road album links at bottom of the view page) What does exactly "then just bogs" mean? The Jeep does not go any faster, or it stalls and stops? What precise noises/knocks and symptoms, etc? On idle, what happens if you press accelerator until above half throttle? Is there a loss of power? If the fuel pressure is low, the engine can run fine upto a point, until the demand for fuel exceeds the supply due to low pressure. |
Re: Lost top end power in 88 Cherokee 4.0.
stilllearning wrote:
> On May 27, 11:20 am, Mike Romain <roma...@sympatico.ca> wrote: >> Ok, I am on a fishing expedition for likely things to check. >> >> Our 88 Cherokee with the 4.0 has lost power above half throttle. It >> goes fine up to that point, then just bogs, no matter what gear it is >> in. It has been neglected for 4 years as far as tuning goes due to me >> not being up to it. >> >> I first changed out the 'very' dirty distributor cap and rotor which >> made starting 'much' faster and smoother. >> >> I then changed the gas filter because it was once again rusted to the >> rot point after about 8 years. >> >> Air filter is new. >> >> I cleaned the connections on the TPS and IAC and verified the TPS >> doesn't have any 'dead' spots with my meter. >> >> I cleaned the CPS and coil connections also. >> >> No joy on any of that. >> >> I have been having some cold idle issues and have been thinking on >> cleaning the IAC, but don't know if that will have a top end effect or not. >> >> I am also thinking on unplugging the EGR just to make sure it isn't >> blown vacuum wise because it only bogs under throttle when things like >> the EGR are active. >> >> Any other ideas? >> >> Mike >> 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 >> 88 Cherokee 235 BFG AT's >> Canadian Off Road Trips Photos: Non members can still view! >> Jan/06http://www.imagestation.com/album/pictures.html?id=2115147590 >> (More Off Road album links at bottom of the view page) > > What does exactly "then just bogs" mean? The Jeep does not go any > faster, or it stalls and stops? What precise noises/knocks and > symptoms, etc? Stalls and stops and sputters until the gas pedal is let up on. No backfires. EGR now unplugged. > > On idle, what happens if you press accelerator until above half > throttle? Is there a loss of power? If I go fast on the pedal, there is a dead spot. No load and smooth pedal seems to work. > > If the fuel pressure is low, the engine can run fine upto a point, > until the demand for fuel exceeds the supply due to low pressure. > I knew there was a reason that filter was the second thing I went after. ;-) I don't have a pressure gauge other than a compression gauge though. I also have verified the coil wire still has a connection with the ohm meter. It is a bit higher per foot in resistance than the plug wires, but only a bit, .7K vs .5K. Hmm the others I have around seem the same too.... I made sure the main power had good connections also. Mike |
Re: Lost top end power in 88 Cherokee 4.0.
stilllearning wrote:
> On May 27, 11:20 am, Mike Romain <roma...@sympatico.ca> wrote: >> Ok, I am on a fishing expedition for likely things to check. >> >> Our 88 Cherokee with the 4.0 has lost power above half throttle. It >> goes fine up to that point, then just bogs, no matter what gear it is >> in. It has been neglected for 4 years as far as tuning goes due to me >> not being up to it. >> >> I first changed out the 'very' dirty distributor cap and rotor which >> made starting 'much' faster and smoother. >> >> I then changed the gas filter because it was once again rusted to the >> rot point after about 8 years. >> >> Air filter is new. >> >> I cleaned the connections on the TPS and IAC and verified the TPS >> doesn't have any 'dead' spots with my meter. >> >> I cleaned the CPS and coil connections also. >> >> No joy on any of that. >> >> I have been having some cold idle issues and have been thinking on >> cleaning the IAC, but don't know if that will have a top end effect or not. >> >> I am also thinking on unplugging the EGR just to make sure it isn't >> blown vacuum wise because it only bogs under throttle when things like >> the EGR are active. >> >> Any other ideas? >> >> Mike >> 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 >> 88 Cherokee 235 BFG AT's >> Canadian Off Road Trips Photos: Non members can still view! >> Jan/06http://www.imagestation.com/album/pictures.html?id=2115147590 >> (More Off Road album links at bottom of the view page) > > What does exactly "then just bogs" mean? The Jeep does not go any > faster, or it stalls and stops? What precise noises/knocks and > symptoms, etc? Stalls and stops and sputters until the gas pedal is let up on. No backfires. EGR now unplugged. > > On idle, what happens if you press accelerator until above half > throttle? Is there a loss of power? If I go fast on the pedal, there is a dead spot. No load and smooth pedal seems to work. > > If the fuel pressure is low, the engine can run fine upto a point, > until the demand for fuel exceeds the supply due to low pressure. > I knew there was a reason that filter was the second thing I went after. ;-) I don't have a pressure gauge other than a compression gauge though. I also have verified the coil wire still has a connection with the ohm meter. It is a bit higher per foot in resistance than the plug wires, but only a bit, .7K vs .5K. Hmm the others I have around seem the same too.... I made sure the main power had good connections also. Mike |
Re: Lost top end power in 88 Cherokee 4.0.
stilllearning wrote:
> On May 27, 11:20 am, Mike Romain <roma...@sympatico.ca> wrote: >> Ok, I am on a fishing expedition for likely things to check. >> >> Our 88 Cherokee with the 4.0 has lost power above half throttle. It >> goes fine up to that point, then just bogs, no matter what gear it is >> in. It has been neglected for 4 years as far as tuning goes due to me >> not being up to it. >> >> I first changed out the 'very' dirty distributor cap and rotor which >> made starting 'much' faster and smoother. >> >> I then changed the gas filter because it was once again rusted to the >> rot point after about 8 years. >> >> Air filter is new. >> >> I cleaned the connections on the TPS and IAC and verified the TPS >> doesn't have any 'dead' spots with my meter. >> >> I cleaned the CPS and coil connections also. >> >> No joy on any of that. >> >> I have been having some cold idle issues and have been thinking on >> cleaning the IAC, but don't know if that will have a top end effect or not. >> >> I am also thinking on unplugging the EGR just to make sure it isn't >> blown vacuum wise because it only bogs under throttle when things like >> the EGR are active. >> >> Any other ideas? >> >> Mike >> 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 >> 88 Cherokee 235 BFG AT's >> Canadian Off Road Trips Photos: Non members can still view! >> Jan/06http://www.imagestation.com/album/pictures.html?id=2115147590 >> (More Off Road album links at bottom of the view page) > > What does exactly "then just bogs" mean? The Jeep does not go any > faster, or it stalls and stops? What precise noises/knocks and > symptoms, etc? Stalls and stops and sputters until the gas pedal is let up on. No backfires. EGR now unplugged. > > On idle, what happens if you press accelerator until above half > throttle? Is there a loss of power? If I go fast on the pedal, there is a dead spot. No load and smooth pedal seems to work. > > If the fuel pressure is low, the engine can run fine upto a point, > until the demand for fuel exceeds the supply due to low pressure. > I knew there was a reason that filter was the second thing I went after. ;-) I don't have a pressure gauge other than a compression gauge though. I also have verified the coil wire still has a connection with the ohm meter. It is a bit higher per foot in resistance than the plug wires, but only a bit, .7K vs .5K. Hmm the others I have around seem the same too.... I made sure the main power had good connections also. Mike |
Re: Lost top end power in 88 Cherokee 4.0.
stilllearning wrote:
> On May 27, 11:20 am, Mike Romain <roma...@sympatico.ca> wrote: >> Ok, I am on a fishing expedition for likely things to check. >> >> Our 88 Cherokee with the 4.0 has lost power above half throttle. It >> goes fine up to that point, then just bogs, no matter what gear it is >> in. It has been neglected for 4 years as far as tuning goes due to me >> not being up to it. >> >> I first changed out the 'very' dirty distributor cap and rotor which >> made starting 'much' faster and smoother. >> >> I then changed the gas filter because it was once again rusted to the >> rot point after about 8 years. >> >> Air filter is new. >> >> I cleaned the connections on the TPS and IAC and verified the TPS >> doesn't have any 'dead' spots with my meter. >> >> I cleaned the CPS and coil connections also. >> >> No joy on any of that. >> >> I have been having some cold idle issues and have been thinking on >> cleaning the IAC, but don't know if that will have a top end effect or not. >> >> I am also thinking on unplugging the EGR just to make sure it isn't >> blown vacuum wise because it only bogs under throttle when things like >> the EGR are active. >> >> Any other ideas? >> >> Mike >> 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 >> 88 Cherokee 235 BFG AT's >> Canadian Off Road Trips Photos: Non members can still view! >> Jan/06http://www.imagestation.com/album/pictures.html?id=2115147590 >> (More Off Road album links at bottom of the view page) > > What does exactly "then just bogs" mean? The Jeep does not go any > faster, or it stalls and stops? What precise noises/knocks and > symptoms, etc? Stalls and stops and sputters until the gas pedal is let up on. No backfires. EGR now unplugged. > > On idle, what happens if you press accelerator until above half > throttle? Is there a loss of power? If I go fast on the pedal, there is a dead spot. No load and smooth pedal seems to work. > > If the fuel pressure is low, the engine can run fine upto a point, > until the demand for fuel exceeds the supply due to low pressure. > I knew there was a reason that filter was the second thing I went after. ;-) I don't have a pressure gauge other than a compression gauge though. I also have verified the coil wire still has a connection with the ohm meter. It is a bit higher per foot in resistance than the plug wires, but only a bit, .7K vs .5K. Hmm the others I have around seem the same too.... I made sure the main power had good connections also. Mike |
Re: Lost top end power in 88 Cherokee 4.0.
> I have no real way to check for fuel pressure I don't think unless one > of my old compression testers could be converted?? > > The miss is pretty consistent. > I would use a guage capable of 100PSI, but your local parts store may rent them. A "miss" and "bogging down" are two different things. If it is a miss, I would change plug wires just to eliminate that possibility, then if not effective, follow the fuel pressure. |
Re: Lost top end power in 88 Cherokee 4.0.
> I have no real way to check for fuel pressure I don't think unless one > of my old compression testers could be converted?? > > The miss is pretty consistent. > I would use a guage capable of 100PSI, but your local parts store may rent them. A "miss" and "bogging down" are two different things. If it is a miss, I would change plug wires just to eliminate that possibility, then if not effective, follow the fuel pressure. |
Re: Lost top end power in 88 Cherokee 4.0.
> I have no real way to check for fuel pressure I don't think unless one > of my old compression testers could be converted?? > > The miss is pretty consistent. > I would use a guage capable of 100PSI, but your local parts store may rent them. A "miss" and "bogging down" are two different things. If it is a miss, I would change plug wires just to eliminate that possibility, then if not effective, follow the fuel pressure. |
Re: Lost top end power in 88 Cherokee 4.0.
> I have no real way to check for fuel pressure I don't think unless one > of my old compression testers could be converted?? > > The miss is pretty consistent. > I would use a guage capable of 100PSI, but your local parts store may rent them. A "miss" and "bogging down" are two different things. If it is a miss, I would change plug wires just to eliminate that possibility, then if not effective, follow the fuel pressure. |
Re: Re: Lost top end power in 88 Cherokee 4.0.
On Sun, 27 May 2007 15:23:32 -0400, Mike Romain <romainm@sympatico.ca>
wrote: >Stalls and stops and sputters until the gas pedal is let up on. > >No backfires. > >EGR now unplugged. Run it hard and make it bog and them pull over and remove a plug and see if it is white or sooty. I tend to think you are getting a fuel starvation here that surfaces at higher power settings. Hard to be sure without feeling it but the plugs would confirm a lean out. Might start by changing fuel filter like someone else suggested and maybe a fuel pressure check too. ----------------- TheSnoMan.com |
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