hesitation off idle and under load when hot
Registered User
Joined: Feb 2003
Posts: 26
Well I must be the founding father of it because I have had the low rpm stumble hesitation for 2 years and 2 months never gets any better and never gets any worse. Bucks and hesitates like crazy at low rpm I too have tried everything but rebuild the engine and nothing works. I have a bunch of mods ready to bolt on and different things planned but until I get this thing fixed I guess those plans will just collect dust. Nothing like crusing town with your car sounding like it's about to sh*@ the bed....
Registered User
Joined: Jun 2003
Posts: 40
From: Illinois
Heat soak is real and my car has problems because of it. It is not a sensor going into closed loop. As a mechanical engineer, I do this stuff for a living and our company is a major supplier to the big three. I have the factory service manual, scanners, voltmeters and so many tools I got tools that fix other tools.
The misfire code, DTC P0300 was read off the car and all the sensors, including the Opt!$park check out perfectly. Only thing I haven't done to trouble shoot is use something like AutoTap to watch all the sensors real time when the problem occurs. Never had a need for the software, but it is the next thing I'll buy to try and solve this problem.
A miss at 2000 rpm is not normal for a LT1, at least not mine anyhow. I've had my car since new and put 95k miles on it, it has never missed at any rpm up to red line until last week. Bouncing off the rev limiter is the only time my LT1 has ever missed a beat in over 7 years.
Everyday I commute 200 miles to work. The car will run perfect the entire trip. But don't let it sit for more than 30 minutes, because the heat soak will make it a dead duck. Once cooled down, all is fine with the world again and you could drive it another 200 miles.
The misfire code, DTC P0300 was read off the car and all the sensors, including the Opt!$park check out perfectly. Only thing I haven't done to trouble shoot is use something like AutoTap to watch all the sensors real time when the problem occurs. Never had a need for the software, but it is the next thing I'll buy to try and solve this problem.
A miss at 2000 rpm is not normal for a LT1, at least not mine anyhow. I've had my car since new and put 95k miles on it, it has never missed at any rpm up to red line until last week. Bouncing off the rev limiter is the only time my LT1 has ever missed a beat in over 7 years.
Everyday I commute 200 miles to work. The car will run perfect the entire trip. But don't let it sit for more than 30 minutes, because the heat soak will make it a dead duck. Once cooled down, all is fine with the world again and you could drive it another 200 miles.
Registered User
Joined: Aug 2002
Posts: 662
From: dallas, tx, usa
Wow, what an awfully long thread but I have to chime in. If the above mentioned items check out I would sugest the MAF. That system will affect both your timing and your air/fuel ratio. It can create a lean situation causing detonation and result in knock retard. It can also cause it to run rich and or retarded across the whole timing table. Yes the O2's monitor the burnt mix but the MAF is a reference before the combustion, the O2's measurment is after the combustion. The MAF should have been equiped with adjustment screw(s) just like a carburator IMHO and for the same reason, every car is a little different.
Registered User
Joined: Feb 2000
Posts: 56
From: Topeka, KS USA
My water pump died which in turn took out my Opti completely. My car wouldn't run period. Bad thing was that I was over a 1000 miles from home at the time. The car gave no warning signs that it was about to breakdown.
Registered User
Joined: Apr 2003
Posts: 1,591
From: PA
Back when i was new to fbodys i always shared my stumble fixing experience over on fbody.com everytime one of these posts would pop up, i guess I'll share it again now.
My car had a bad stumble when i got it, very temperature dependent. In the early summer it would run ok, but as the summer got hotter the stumble got much worse. It was very dependent on operating temperatures, especially above the ~185 mark.
Online everyone told me it was the opti. I took it to the local cadillac/pontiac dealer which is very reputable. Either because my dad has done buisiness there in the past, or because they new i was going to do the work myself and wasn't going to pay them to fix it, they let me in on a little secret, opti's aren't that bad. Many many times people replace the opti and decide to do plugs wires and coil at the same time. Replacing the opti doesn't fix the stumble, it's the other ignition parts. I replaced only the coil, plugs and wires on mine and it was all better, no need to f- with the opti. I'm not saying that an opti has never gone bad, but without a major waterleak on them they just aren't as bad as everyone makes them out to be. Dealers like to make a lot of money on them. When i did my plugs i found that they didn't look bad, but the gap on all of them was opened up way out of spec. My car had ~53k mi on it at the time and none of that stuff had been replaced. Now don't even get me started on how much of a PITA replacing the plug/wires was for the first time.
good luck all you stumblers, (knock on wood)
-brent
My car had a bad stumble when i got it, very temperature dependent. In the early summer it would run ok, but as the summer got hotter the stumble got much worse. It was very dependent on operating temperatures, especially above the ~185 mark.
Online everyone told me it was the opti. I took it to the local cadillac/pontiac dealer which is very reputable. Either because my dad has done buisiness there in the past, or because they new i was going to do the work myself and wasn't going to pay them to fix it, they let me in on a little secret, opti's aren't that bad. Many many times people replace the opti and decide to do plugs wires and coil at the same time. Replacing the opti doesn't fix the stumble, it's the other ignition parts. I replaced only the coil, plugs and wires on mine and it was all better, no need to f- with the opti. I'm not saying that an opti has never gone bad, but without a major waterleak on them they just aren't as bad as everyone makes them out to be. Dealers like to make a lot of money on them. When i did my plugs i found that they didn't look bad, but the gap on all of them was opened up way out of spec. My car had ~53k mi on it at the time and none of that stuff had been replaced. Now don't even get me started on how much of a PITA replacing the plug/wires was for the first time.
good luck all you stumblers, (knock on wood)
-brent
Registered User
Joined: Jan 2003
Posts: 83
From: Greenville, SC
My car pulled the following codes: 141, 300, and 400. All of these had to do with a misfire condition (duh!), EGR, and and O2 sensor. We streamed realtime data and found cylinders 2 and 7 were misfiring. Lifted the car, cheked the cap and plug wires and found number 7 was touching the bolt of the flange where header and y-pipe come together. Pulled it off, shielded it, and no probs since last night. Pulled #2, made sure it was clean, and put it back. So far so good! No more codes yet, and it's running like it's supposed to!
I'm putting O2 sims on this weekend, so hopefully that'll clear up that prob. I pulled off the EGR and made sure it was clear. We'll see...
Marcus
I'm putting O2 sims on this weekend, so hopefully that'll clear up that prob. I pulled off the EGR and made sure it was clear. We'll see...
Marcus
Registered User
Joined: Jun 2003
Posts: 45
From: Lawrenceville, GA
Well I replaced the intake gasket last night! WOW that was fun. Hopefully this fixes it! I noticed it was leakin a bunch of oil into the intake ports on the heads. Which would cause the car to hesitate
and burn a bunch of oil! Esspecialy when its hot because everythang heats up and expands thus allowing more oil into the cylinders. I will let you know if it fixed the hesitation.
and burn a bunch of oil! Esspecialy when its hot because everythang heats up and expands thus allowing more oil into the cylinders. I will let you know if it fixed the hesitation.
Registered User
Joined: Aug 2002
Posts: 2,325
From: BC
Originally posted by 94GreenZ28
I know how you guys feel. I'm the king of Low RPM Stumbles. I've had it for over a year now and I've done everything except for rebuilding the engine. You guys might want to search for some posts under my name. There's alot of good info in them.
I know how you guys feel. I'm the king of Low RPM Stumbles. I've had it for over a year now and I've done everything except for rebuilding the engine. You guys might want to search for some posts under my name. There's alot of good info in them.
Registered User
Joined: Dec 2001
Posts: 180
From: Texas
Originally posted by SinisterSS
Heat soak is real and my car has problems because of it. It is not a sensor going into closed loop. As a mechanical engineer, I do this stuff for a living and our company is a major supplier to the big three. I have the factory service manual, scanners, voltmeters and so many tools I got tools that fix other tools.
The misfire code, DTC P0300 was read off the car and all the sensors, including the Opt!$park check out perfectly. Only thing I haven't done to trouble shoot is use something like AutoTap to watch all the sensors real time when the problem occurs. Never had a need for the software, but it is the next thing I'll buy to try and solve this problem.
A miss at 2000 rpm is not normal for a LT1, at least not mine anyhow. I've had my car since new and put 95k miles on it, it has never missed at any rpm up to red line until last week. Bouncing off the rev limiter is the only time my LT1 has ever missed a beat in over 7 years.
Everyday I commute 200 miles to work. The car will run perfect the entire trip. But don't let it sit for more than 30 minutes, because the heat soak will make it a dead duck. Once cooled down, all is fine with the world again and you could drive it another 200 miles.
Heat soak is real and my car has problems because of it. It is not a sensor going into closed loop. As a mechanical engineer, I do this stuff for a living and our company is a major supplier to the big three. I have the factory service manual, scanners, voltmeters and so many tools I got tools that fix other tools.
The misfire code, DTC P0300 was read off the car and all the sensors, including the Opt!$park check out perfectly. Only thing I haven't done to trouble shoot is use something like AutoTap to watch all the sensors real time when the problem occurs. Never had a need for the software, but it is the next thing I'll buy to try and solve this problem.
A miss at 2000 rpm is not normal for a LT1, at least not mine anyhow. I've had my car since new and put 95k miles on it, it has never missed at any rpm up to red line until last week. Bouncing off the rev limiter is the only time my LT1 has ever missed a beat in over 7 years.
Everyday I commute 200 miles to work. The car will run perfect the entire trip. But don't let it sit for more than 30 minutes, because the heat soak will make it a dead duck. Once cooled down, all is fine with the world again and you could drive it another 200 miles.
I don't think anyone was saying heat soak is not real. I think what we are saying is that SOME may be thinking their missing problems are heat soak, when something else is the problem, such as a wires , sensors , computer, grounds, etc.
Registered User
Joined: Jun 2003
Posts: 45
From: Lawrenceville, GA
Well the car still burns oil when it gets hot! Now iI think oil is gettin into the cylinders some other way! And causing a stumble . Because it runs fine till it gets hot and thats when the stumble happens and when it starts to burn oil.! Who knows i am at a lose here!
Registered User
Joined: Aug 2002
Posts: 662
From: dallas, tx, usa
Well the car still burns oil when it gets hot! Now iI think oil is gettin into the cylinders some other way! And causing a stumble . Because it runs fine till it gets hot and thats when the stumble happens and when it starts to burn oil.! Who knows i am at a lose here!