Car stumbles
Thread Starter
Safety Car
Joined: Mar 2005
Posts: 4,723
Likes: 11
From: Winnipeg Manitoba, Canada
Car stumbles
I've been trying to find the cause of the my stumble on acceleration for a few weeks. The car doesnt do it all the time, but it does it alot. I've replaced the plugs, wires, coil, cap, rotor, iginition module, fuel pump and all filters. When the car acts up my fuel pressure is solid. I've put a can of injector cleaner in with a new tank of gas. The only code the car had was code 42, which is the EST circuit. I've cleared the code and it hasn't returned in a few days. Any other ideas? I'm trying to get my hands on a laptop to scan and see exactly what is going on.
The engine was rebuilt last year and I had it tuned. Is it possible the car needs to be retuned?
The engine was rebuilt last year and I had it tuned. Is it possible the car needs to be retuned?
Safety Car
Joined: Oct 2007
Posts: 3,816
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From: :45 minutes from everywhere / E-I-E-I-O
We know that one problem seems to be the distributor holddown fork.
Were you able to get that to get a lockdown on the distributor? I wouldn't do any grinding - I would shim the 'handle' end, before grinding...
Were you able to get that to get a lockdown on the distributor? I wouldn't do any grinding - I would shim the 'handle' end, before grinding...
Last edited by schrade; Aug 4, 2008 at 12:18 AM.
Thread Starter
Safety Car
Joined: Mar 2005
Posts: 4,723
Likes: 11
From: Winnipeg Manitoba, Canada
I got it to fit alot better. It actually lines up and holds the distributor properly. I don't have a shim or washer underneath though. I checked the timing a few times after I drove it and the timing hasnt moved.
My bracket looks slightly different from the one in the picture.
My bracket looks slightly different from the one in the picture.
Thread Starter
Safety Car
Joined: Mar 2005
Posts: 4,723
Likes: 11
From: Winnipeg Manitoba, Canada
My fuel pressure also sits at 40psi with the vacuum line connected and abouyt 45psi with the disconnected.
Safety Car
Joined: Oct 2007
Posts: 3,816
Likes: 0
From: :45 minutes from everywhere / E-I-E-I-O
I got it to fit alot better. It actually lines up and holds the distributor properly. I don't have a shim or washer underneath though. I checked the timing a few times after I drove it and the timing hasnt moved.
My bracket looks slightly different from the one in the picture.
My bracket looks slightly different from the one in the picture.
On a '94, and probably other years too, DTC 42 does NOT light SES light - IF your 42 is ICC ground fault, that is...
Advanced
Joined: Jul 2008
Posts: 51
Likes: 0
The EFI temp sensor? It can sporadically send the car rich or lean. Also, since you got a spark code (and you know it wasn't set when you unplugged the jumper to set the timing) you might replace the EST controller. When I bought my vette used it had 3 old EST controllers in the console. I imagine the previous owner had code 42 problems.
Thread Starter
Safety Car
Joined: Mar 2005
Posts: 4,723
Likes: 11
From: Winnipeg Manitoba, Canada
The EFI temp sensor? It can sporadically send the car rich or lean. Also, since you got a spark code (and you know it wasn't set when you unplugged the jumper to set the timing) you might replace the EST controller. When I bought my vette used it had 3 old EST controllers in the console. I imagine the previous owner had code 42 problems.
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Thread Starter
Safety Car
Joined: Mar 2005
Posts: 4,723
Likes: 11
From: Winnipeg Manitoba, Canada
Advanced
Joined: Jul 2008
Posts: 51
Likes: 0
90-92 its built into the ECM. Earlier versions are a 1.5x1.5 inch box mounted on the blower motor housing. I don't know if there is any really good way to test it since your problem is sporadic. One way to tell for certain that its working is by tapping the right cylinder head with a small hammer while watching the timing. If it retards, the system, including the EST, is working... at that moment.
They are fairly cheap and easy to replace if you have the early version.
google "esc module" and you can find more info on it.
They are fairly cheap and easy to replace if you have the early version.
google "esc module" and you can find more info on it.
Thread Starter
Safety Car
Joined: Mar 2005
Posts: 4,723
Likes: 11
From: Winnipeg Manitoba, Canada
90-92 its built into the ECM. Earlier versions are a 1.5x1.5 inch box mounted on the blower motor housing. I don't know if there is any really good way to test it since your problem is sporadic. One way to tell for certain that its working is by tapping the right cylinder head with a small hammer while watching the timing. If it retards, the system, including the EST, is working... at that moment.
They are fairly cheap and easy to replace if you have the early version.
google "esc module" and you can find more info on it.
They are fairly cheap and easy to replace if you have the early version.
google "esc module" and you can find more info on it.
My car is a 90 so I guess its built into the ECM. So does the whole ECM need to be replaced?
Le Mans Master
Joined: Oct 2003
Posts: 6,130
Likes: 2
From: seattle WA
Yes on the fuel pressure. You mentioned your TPS is set at .54 volts, but have you checked it all the way through? the base setting you have is good, but it should increase as throttle opens, I think to 5 volts (double check that) and it should be a smooth increase.
Thread Starter
Safety Car
Joined: Mar 2005
Posts: 4,723
Likes: 11
From: Winnipeg Manitoba, Canada
Yes on the fuel pressure. You mentioned your TPS is set at .54 volts, but have you checked it all the way through? the base setting you have is good, but it should increase as throttle opens, I think to 5 volts (double check that) and it should be a smooth increase.
Thread Starter
Safety Car
Joined: Mar 2005
Posts: 4,723
Likes: 11
From: Winnipeg Manitoba, Canada
Well I checked my TPS voltage and it goes up at a steady rate. Starts off a .54v and goes up to 4.6v.
I checked all my fuel injectors and they were all 15.2ohms so they seem good.
Lately my car seems to be doing the stumble all the time. You can even hear it in the exhaust at idle.
The engine was rebuilt and beefed up a bit. Is it possible I need to increase the fuel pressure or timing? Since the distributor was loose, can the teeth be worn or somthing along those lines?
I checked all my fuel injectors and they were all 15.2ohms so they seem good.
Lately my car seems to be doing the stumble all the time. You can even hear it in the exhaust at idle.
The engine was rebuilt and beefed up a bit. Is it possible I need to increase the fuel pressure or timing? Since the distributor was loose, can the teeth be worn or somthing along those lines?
Safety Car
Joined: Oct 2007
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From: :45 minutes from everywhere / E-I-E-I-O
If yours is perfectly in sync, that will lead to look at what they have in common in the schematic.
Mine was sync'ed, and that was more confirmation of my PCM problem, since it is the only thing they have in common.
Mine was sync'ed, and that was more confirmation of my PCM problem, since it is the only thing they have in common.