L98 codes - running rough.
Thread Starter
Instructor
Joined: May 2005
Posts: 182
Likes: 0
From: Glendale AZ
L98 codes - running rough.
91 L98. She was running great, occasionally giving me a 32 code - but not consistently.
Now it has a rough idle, and i am pulling a 33, and 44 code. In the anemic book i have the codes are very general.
Anyone have any ideas what i might be experiencing?
Now it has a rough idle, and i am pulling a 33, and 44 code. In the anemic book i have the codes are very general.
Anyone have any ideas what i might be experiencing?
Le Mans Master
Joined: Oct 2003
Posts: 6,130
Likes: 2
From: seattle WA
Code 32-EGR valve or switch, most likely switch, code 33 Mass Air Flow sensor-probably and hopefully a relay-could be the burn off, power or FP relay. Code 44, Electronic Spark Control (ESC) Circuit-on that I'd probably check the Knock sensor wires. Do you have a Helms, it's full of trouble shooting flow charts and is worth it's weight in gold for us vette owners.
Thread Starter
Instructor
Joined: May 2005
Posts: 182
Likes: 0
From: Glendale AZ
i dont have MAF on a 91 - just MAP. Not sure how to check that. I do not have a helms, but i do have the dealer service manuals - but i couldnt find codes listed anywhere in there.....
Thread Starter
Instructor
Joined: May 2005
Posts: 182
Likes: 0
From: Glendale AZ
yup - those are the codes i read too
now what in the hell does one do about them.
Map high voltage low vaccuum - don't have the slightest clue how to start troubleshooting that.......
and the 44 code seems unlikely to be a failed o2 sensor - since its brand new.
I am just looking for some real world ideas on where to start - i had hoped my service manuals would push me in the right way - but again they dont appear to deal with codes at all - unless someone can tell me where i am missing them at.
Thanks again for all the help guys
now what in the hell does one do about them.
Map high voltage low vaccuum - don't have the slightest clue how to start troubleshooting that.......
and the 44 code seems unlikely to be a failed o2 sensor - since its brand new.
I am just looking for some real world ideas on where to start - i had hoped my service manuals would push me in the right way - but again they dont appear to deal with codes at all - unless someone can tell me where i am missing them at.
Thanks again for all the help guys
Racer
Joined: Feb 2004
Posts: 265
Likes: 1
From: Irwindale Ca
Id say the Exhaust Gas Recirculation Device EGR is sticking open. This is a shot in the dark though, My L98 has never had those codes but a lean mixture would be a air leak like the EGR stuck open. O2 sensor is just telling you that you have a lean mixture. Low vaccum , High vaccum , vaccum fluxuations. I know there is only one throttle body but picture the EGR hole acting as another throttle body. Might be time for a new EGR My guess.. <waiting for others to chime in>
Drifting
Joined: Mar 2005
Posts: 1,923
Likes: 0
From: GA
Originally Posted by sremenap
Map high voltage low vaccuum - don't have the slightest clue how to start troubleshooting that.......
Personally, I would try a MAP sensor (they cost about $40) and if it doesn't cure the problem I'd have an extra sensor for troubleshooting later down the road. I don't consider this as "throwing parts at it" as I like to have a spare for each of my sensors (except MAF..too expensive to have laying around), because they will always break when the parts stores are closed.
Le Mans Master
Joined: Oct 2003
Posts: 6,130
Likes: 2
From: seattle WA
Sorry about the MAF-MAP thingy, they had MAP in 84 and I didn't realize they were using MAP after 1990. But I'd still bet on the EGR switch rather than the EGR solenoid, and it sounds like you're running in open loop ("running rough") there I would suspect the MAP sensor-but I'd check vacumn hoses first.
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CF Community Team
Joined: Nov 2005
Posts: 5,207
Likes: 2,862
From: Charlotte N.C.
I'm new to cars that have engine codes, I have a 92, how do you pull codes and on a trip to florida yesterday from Charlotte I had the service engine soon light come on, it came on the first time about an hour into the trip and then after I filled the fuel tank twice it was off when I started the car but would come back on after about ten miles. Now that I'm down here I've taken a few short 30-50 mile trips and it hasn't come on. I know that the gas cap seal affects it and I have a good seal because it hisses when I open it. I also know it could be an O2 sensor and a couple other things but should'nt I be able to pull codes to figure out what it is?
Le Mans Master
Joined: Oct 2003
Posts: 6,130
Likes: 2
From: seattle WA
Yes-you can pull codes. Here's a good site for us.
http://www.c4vettes.com/ecm.htm
Good for 1985-1993 C4s
Good Luck and Merry Christmas
http://www.c4vettes.com/ecm.htm
Good for 1985-1993 C4s
Good Luck and Merry Christmas
Racer
Joined: Nov 2005
Posts: 456
Likes: 3
From: Sumner Texas
I strongly suspect that you have a significant vacuum leak somewhere. The EGR valve can act as a vacuum leak when it is open when it should not be.
Put a vacuum gauge on and start from there. You can use a long piece of hose with one end to your ear and the other end as a probe around places where you could possibly have a vacuum leak. When you get to the leak with the probe end of your hose, you will here a hissing.
I have an old stethoscope that I cut the sensor off the end and put on a longer piece of hose past the Y to use as a probe for finding vacuum leaks. It works great.
Good luck and keep us posted.
Merry Christmas,
Put a vacuum gauge on and start from there. You can use a long piece of hose with one end to your ear and the other end as a probe around places where you could possibly have a vacuum leak. When you get to the leak with the probe end of your hose, you will here a hissing.
I have an old stethoscope that I cut the sensor off the end and put on a longer piece of hose past the Y to use as a probe for finding vacuum leaks. It works great.
Good luck and keep us posted.
Merry Christmas,
Instructor
Joined: Aug 2005
Posts: 206
Likes: 1
From: Milwaukee WI
