erratic running
Thread Starter
Heel & Toe
Joined: Oct 2006
Posts: 19
Likes: 0
erratic running
my 1992 LT1 has developed an erratic running problem.
it is fine when starting from cold but may develop after running
for 5 minutes, other times it is fine all the time.
it arrives by having no acceleration and poor idling in drive at stop
junctions.(it sounds like a misfire or blockage)
i have replaced the fuel filter but seems to be no better.
like i say it does not happen all the time.
could anyone help please.
it is fine when starting from cold but may develop after running
for 5 minutes, other times it is fine all the time.
it arrives by having no acceleration and poor idling in drive at stop
junctions.(it sounds like a misfire or blockage)
i have replaced the fuel filter but seems to be no better.
like i say it does not happen all the time.
could anyone help please.
Race Director
Joined: Dec 2006
Posts: 10,383
Likes: 4
Next steps:
Pull codes and see what they offer.
Run a can of SeaFoam or Techron through the tank.
Use a mechanic's stethoscope or a 3' length of garden hose to listen to each injector firing.
Check fuel pressure at the shredder valves on each fuel rail.
Check plugs against pics to see if there is any fouling.
Clean the intake including the TB housing. Careful not to clean the MAF.
Check each plug wire for spark at idle and at 2k RPMS with timing light.
When has the opti been changed?
Pull codes and see what they offer.
Run a can of SeaFoam or Techron through the tank.
Use a mechanic's stethoscope or a 3' length of garden hose to listen to each injector firing.
Check fuel pressure at the shredder valves on each fuel rail.
Check plugs against pics to see if there is any fouling.
Clean the intake including the TB housing. Careful not to clean the MAF.
Check each plug wire for spark at idle and at 2k RPMS with timing light.
When has the opti been changed?
Thread Starter
Heel & Toe
Joined: Oct 2006
Posts: 19
Likes: 0
thanks for your advice.
i am in the u.k and don't have access locally to any diagnostics.
could you explain what you mean by a couple of things
what is seafoam?
check plugs against pics?
i have no history of the car prior to me buying it in october '06
so the opti-spark could be the original for all i know.
i am in the u.k and don't have access locally to any diagnostics.
could you explain what you mean by a couple of things
what is seafoam?
check plugs against pics?
i have no history of the car prior to me buying it in october '06
so the opti-spark could be the original for all i know.
Instructor
Joined: Aug 2006
Posts: 121
Likes: 0
I had similar symptoms and I needed new fuel injectors.
Seafoam is a fuel cleaner additive I believe. The fuel injectors make a ticking sound - the other post want you to listen to each ijector to see if they are ticking. You may also have a bad spark plug wire or fouled spark plug. If the injectors are bad, sometimes a plug will be fouled with too much gas. Pulling the plug and seeing this is an indication of a bad injector. The fuel pressue gauge can help also - if you hook it up you should be at 42lbs of pressure approx. If you shut the car off and the pressure drops quickly it may also be a bad injector. This extra gas is getting on the plugs.
There is a lot you can do yourself to diagnose. Sounds like injectors to me - will cost about $900 installed for aftermarkets (not genuine GM)
Good luck
Seafoam is a fuel cleaner additive I believe. The fuel injectors make a ticking sound - the other post want you to listen to each ijector to see if they are ticking. You may also have a bad spark plug wire or fouled spark plug. If the injectors are bad, sometimes a plug will be fouled with too much gas. Pulling the plug and seeing this is an indication of a bad injector. The fuel pressue gauge can help also - if you hook it up you should be at 42lbs of pressure approx. If you shut the car off and the pressure drops quickly it may also be a bad injector. This extra gas is getting on the plugs.
There is a lot you can do yourself to diagnose. Sounds like injectors to me - will cost about $900 installed for aftermarkets (not genuine GM)
Good luck
Race Director
Joined: Dec 2006
Posts: 10,383
Likes: 4
Just about every chilton or haynes manual has pictures of sparkplugs in it with various failure symptoms.
This site has a few to look at as well.
Seafoam is a company that makes a good fuel system cleaner.
This site has a few to look at as well.
Seafoam is a company that makes a good fuel system cleaner.
Instructor
Joined: Aug 2006
Posts: 121
Likes: 0
My fuel injector symptoms were intermittent. Sometime the car ran fine. Other times, after it was warm, it would want to stall at a light, or would be almost stalling when I returned home. I paid for a diagnostic. It was a leaking injector and the car runs fine now. I had the slight hesitation during cruising and the "erratic" idle at various times. Not saying this is your case for sure - read these posts and we can narrow done the problem.
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Thread Starter
Heel & Toe
Joined: Oct 2006
Posts: 19
Likes: 0
I haven't had a chance to check out your suggestions yet,
but i did notice a small puddle of water under the car at the weekend
and traced it to the water pump.
could this be causing my intermittent problem by dripping onto the
opti spark?. I have ordered a new pump which should arrive next week -
they have them in stock over here (uk).
but i did notice a small puddle of water under the car at the weekend
and traced it to the water pump.
could this be causing my intermittent problem by dripping onto the
opti spark?. I have ordered a new pump which should arrive next week -
they have them in stock over here (uk).
Le Mans Master
Joined: Jan 2006
Posts: 5,621
Likes: 206
From: Orlando FL
You have the onset of classic opti problems. I chased some similar problems and ended up changing my opti. After I heated up, I would kick and buck when I accelerated. The idle eventually got erratic. The symptoms can vary much.
It’s a possibility the water pump leak could be part of the problem, hard to definitely make the association. My pump leaked also but did not affect the opti. My opti went out at another time. But we all know the possible effects of water on the opti. Most people who kill their opti usually wash it with high pressure water from a hose which is quite different than just some coolant leaking on it. But with miles and time on it, it just might be ready to be replaced. Mine lasted about 95,000 miles.
On the 80 models they had bad injectors which many know of these problem. But with 92 and up the injectors are different and much more reliable and trouble free.
About 6 months ago a 94 had what seemed to have opti problems but actually had a clogged cat. The symptoms were similar and something just to consider.
It’s a possibility the water pump leak could be part of the problem, hard to definitely make the association. My pump leaked also but did not affect the opti. My opti went out at another time. But we all know the possible effects of water on the opti. Most people who kill their opti usually wash it with high pressure water from a hose which is quite different than just some coolant leaking on it. But with miles and time on it, it just might be ready to be replaced. Mine lasted about 95,000 miles.
On the 80 models they had bad injectors which many know of these problem. But with 92 and up the injectors are different and much more reliable and trouble free.
About 6 months ago a 94 had what seemed to have opti problems but actually had a clogged cat. The symptoms were similar and something just to consider.
Last edited by pcolt94; Feb 8, 2007 at 12:10 PM.