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jerky idle

C

cokays

Guest
1994 at idle seems to be missing. While sitting at at lights or stop signs car will jerk and shake, sometimes worst than others.
When I take it out of gear I can still feel it but not as bad. Took it to the dealership and they claimed they could not find a problem.
They said to bring it back when it was worst. Car use to run great. All this started about a month or 2 ago. It is getting worst.
 

c4c5specialist

Technical Advisor
Joined
May 29, 2001
Messages
3,682
Location
New Haven, Ct. USA
Corvette
Nope, but someday.
Questions please

Hi there, and welcome,
Well, I have a few questions here, first which engine do you have, LT1 I suppose??
Second, what is your mileage???
Third, what repairs have been done to the car recently??
Fourth, Does the car seem to have lost some of its power??
Please answer these questions, and we can proceed.
Best to ya, c4c5
 
C

cokays

Guest
reply

I do have the LT1. Mileage is approx. 26,000. No repairs have been done to the car recently. It does seem to have lost power. When I accelerate it almost sounds like a a carb that isn't quite opening all the way. If I'm correct a car with fuel injection does not have a carb right??????? I stored the car last winter. When I brought it out last spring I had some problems with moisture in the gas. A can of fuel additive for fuel injection systems did the trick. Then about 2 months later all of the above started to happen. One more thing, When rapid accelerating can here a little ping like low octane gas but that is not the case. Appreciate your time.

Thanks,
Kevin
 

Edmond

Well-known member
Joined
Aug 1, 2001
Messages
5,218
Location
Louisiana
Corvette
2003 Z06
cokays,

Do you just store it over the winter or do you occasionally start it up and let it run for a little bit. I'm here in Illinois and we both get pretty bad winters. I just start the car up every day and let it run until the coolant temp. gets to 150 so the car doesn't stay too cold for too much of an extended period.

Dealer couldn't find anything wrong with the idle? You should check into the fuel injectors and the O2 sensor. I think the O2 sensor is overlooked, but it does regulate the air/fuel mixture!
 
C

cokays

Guest
Actually I store it in my inlaws garage up north. No oportunity to start it every day. I was considering having the fuel injectors checked. The idea of checking the 02 sensor seems like a good one. Thanks for the info.
 

c4c5specialist

Technical Advisor
Joined
May 29, 2001
Messages
3,682
Location
New Haven, Ct. USA
Corvette
Nope, but someday.
a few suggestions

Hi there,
Well, first thing that I would try is to put a can of fuel injector cleaner in at your next tank. 12345515 from any GM dealer works well, and should only be used once every six months.
Next, have you at any time gotten any foul smells out of the exhaust, like sulfur type.
I feel that you may be dealing with a missing low resolution signal from the optispark, however, I would like you to try this before proceeding with replacing parts.
While 02 sensors do wear out, and should be changed every 40k, this should NOT cause the condition here, as only if you were running so lean, that you have a missfire, due to no gas being commanded into the cylinders.
please let usknow, c4c5
 

JT ZR-Won

Well-known member
Joined
Dec 6, 2000
Messages
1,273
Location
Bradenton, FL
Corvette
'90 ZR-1 #365 (SOLD...but Dad's got it now)
Welcome to the CAC cokays!

c4c5,
Would fouled out plugs or a clogged fuel filter possibly cause those symptoms also? I have had similiar problems in the past and it was usually one of two things: spark or fuel
I know that it couldn't hurt to put in new plugs and fuel filter as they are inexpensive and easy to do.............and with 26,000 miles, it is probably time.
Also, you mentioned Optispark..........I've heard of people having a lot of problems with this setup. Any type of moisture (especially if the car sits over winter) can kill the optispark........

Jay
 
C

cokays

Guest
This is strange. Along with the rough idle I've noticed at times when I accelerate I get some pinging or rattling and no power. Other times along with the rough idle I get great acceleration with no pinging or rattling?????? Looking for as many possibilities as I can get before I take it in to the garage. I have put fuel injector cleaner/dry gas in the tank within the last couple of weeks and have experienced no change. Thanks all for your input. Have a good day.
 

c4c5specialist

Technical Advisor
Joined
May 29, 2001
Messages
3,682
Location
New Haven, Ct. USA
Corvette
Nope, but someday.
Hi again,
JT is close on this, as your clue here could be the detonation, and loss of power, could be as result of a clogged fuel filter, or low fuel pressure. I would pursue this course of action first, as your detonation is usually as result of a lean condition.
If your EGR valve was NOT working, it would happen all the time. Your ignition retards the timing when knock is sensed, therefore, a loss of power is felt.
Just thoughts, as for now, I would have someone correctly diagnose the knock condition, and my guess is that this could be your issue.
Best to you, c4c5
 

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