:banghead:
I've been reading many threads on here of folks having issues with their Caddy failing to accelerate on the highway. I've got the same problem, but have yet to see any final outcomes of the debug of this problem.
I've got a 1994 Sedan Deville with the 4.9L with 175K miles. Car is in great shape but becoming more and more undriveable.
Like many have said the car starts fine, idles fine and basically runs fine until something gets hot or tired. At that point, the car will no longer accelerate at highway speeds and seems very sluggish at low speeds. It basically just backs down when pressing on the gas pedal instead of speeding up. The harder you press the slower you go. No back firing, no stumbling, no transmission slipping...but it simply acts like the air or fuel is simply getting cut off. It can not pull up a hill hardly at all and will back all the way down to 15mph once this starts. Previous to getting into this mode, the car runs virtually flawless. You can throw the car into neutral while it is backing down and the engine revs fine without any gas smoke or anything. Put it back into drive and the engine will again back down to a crawl if more pedal is applied. Letting off the gas pedal to a certain point will allow the car to keep going at that speed but it will not accelerate past a certain throttle position. The longer it goes the less throttle I can apply before it backs down. Therefore, at some point, I'm going like 15mph on the highway and mashing the gas tries to almost kill the car. Pull over to the side and engine revs flawlessly. Actually, I've gotten into the mode of pulling over, putting it in neutral, rev the engine a few times, put it in drive and can get maybe 10miles before it does it again. Got to be the wierdest thing I've ever seen.
The only codes ever posted were P042 and P044 History saying that the oxygen sensor is reading lean. I cleared the codes many weeks ago and they have not returned nor have any other codes, but the car still will not accelerate once hot and/or tired.
Fuel pressure reads 40psi at idle or at full speed. The fuel pump is under 1year old.
MAP sensor - No codes posted...not sure it can be this without codes.
MAF sensor - No codes posted...not sure it can be this without codes.
TPS sensor - No codes posted...not sure it can be this without codes.
Ignition Coil - Humm? Maybe ... anyway to tell if it only fails while at full speed. Hard to be under the hood at 70mph.
EGR Valve?
Had a great garage tech look it over for nearly a week and basically said that all the sensors seem to measure good and basically didn't install a single component because he didn't know what to replace and didn't want to start shot gunning parts at it. He did drive it until it started happening and said that the fuel pressure was dead perfect during the problem. He wants me to drive it more and see if something decides to completely fail or post a code to give us a hint.
Any ideas?
I've been reading many threads on here of folks having issues with their Caddy failing to accelerate on the highway. I've got the same problem, but have yet to see any final outcomes of the debug of this problem.
I've got a 1994 Sedan Deville with the 4.9L with 175K miles. Car is in great shape but becoming more and more undriveable.
Like many have said the car starts fine, idles fine and basically runs fine until something gets hot or tired. At that point, the car will no longer accelerate at highway speeds and seems very sluggish at low speeds. It basically just backs down when pressing on the gas pedal instead of speeding up. The harder you press the slower you go. No back firing, no stumbling, no transmission slipping...but it simply acts like the air or fuel is simply getting cut off. It can not pull up a hill hardly at all and will back all the way down to 15mph once this starts. Previous to getting into this mode, the car runs virtually flawless. You can throw the car into neutral while it is backing down and the engine revs fine without any gas smoke or anything. Put it back into drive and the engine will again back down to a crawl if more pedal is applied. Letting off the gas pedal to a certain point will allow the car to keep going at that speed but it will not accelerate past a certain throttle position. The longer it goes the less throttle I can apply before it backs down. Therefore, at some point, I'm going like 15mph on the highway and mashing the gas tries to almost kill the car. Pull over to the side and engine revs flawlessly. Actually, I've gotten into the mode of pulling over, putting it in neutral, rev the engine a few times, put it in drive and can get maybe 10miles before it does it again. Got to be the wierdest thing I've ever seen.
The only codes ever posted were P042 and P044 History saying that the oxygen sensor is reading lean. I cleared the codes many weeks ago and they have not returned nor have any other codes, but the car still will not accelerate once hot and/or tired.
Fuel pressure reads 40psi at idle or at full speed. The fuel pump is under 1year old.
MAP sensor - No codes posted...not sure it can be this without codes.
MAF sensor - No codes posted...not sure it can be this without codes.
TPS sensor - No codes posted...not sure it can be this without codes.
Ignition Coil - Humm? Maybe ... anyway to tell if it only fails while at full speed. Hard to be under the hood at 70mph.
EGR Valve?
Had a great garage tech look it over for nearly a week and basically said that all the sensors seem to measure good and basically didn't install a single component because he didn't know what to replace and didn't want to start shot gunning parts at it. He did drive it until it started happening and said that the fuel pressure was dead perfect during the problem. He wants me to drive it more and see if something decides to completely fail or post a code to give us a hint.
Any ideas?
