Engine runs rough no codes
Thread Starter
Heel & Toe
Joined: Aug 2005
Posts: 16
Likes: 0
Engine runs rough no codes
2000 C5 A4 all stock 78000 miles. car runs like a top at over 2500 rpm. At low speed, either at idle or stoping or acceleration it will stumble lose power and all most die. no check engine lite or codes. Car will run fine for 25 or 50 miles stop and go fine. then problem will return. Please help.
Last edited by kggunter; Jan 30, 2007 at 11:27 PM.
Pro
Joined: Apr 2006
Posts: 552
Likes: 0
From: Alton Illinois
no one has posted so i thought i would at least let you know that i am sure someone will pick it up soon. i imagine most of the knowledgeable ones need to see codes and it is hard to imagine that the car can run that badly without throwing codes all over the place. are you sure there are no codes using the code reading process on the dic? how have you read the codes? at least this may get the ball rolling.
good luck!
jim
good luck!
jim
Pro
Joined: Apr 2006
Posts: 552
Likes: 0
From: Alton Illinois
ok, sounds like the code reading is ok. sorry for checking the obvious but you never know! this is really a poke and hope problem! maybe someone can give you a place to start. does it do it with or without a load? i mean in neutral as well as wheels turning?
jim
jim
Drifting
Joined: May 2003
Posts: 1,715
Likes: 1
From: cAshburn VA
Pull and inspect the plugs, do a resistance test on your wires, failing that check for vacuum leaks. Always a good, easy and inexpensive place to start.
Inspect and clean the throttle body, airbox and filter too!
Not and expert, just my $.02... Hope that helps!
Oh, if you have recently put in a 242 248 cam with 600+ lift on a 110 lsa, it might be that! No? was a thought...
If you are anywhere near Northern Virginia be glad to help you out, even if its just to pop-a-top and sympathize, heh.
Inspect and clean the throttle body, airbox and filter too!
Not and expert, just my $.02... Hope that helps!
Oh, if you have recently put in a 242 248 cam with 600+ lift on a 110 lsa, it might be that! No? was a thought...
If you are anywhere near Northern Virginia be glad to help you out, even if its just to pop-a-top and sympathize, heh.
Last edited by IFLUBYU; Jan 30, 2007 at 11:16 PM.
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Le Mans Master
Joined: May 2006
Posts: 5,987
Likes: 18
From: DuBois PA
St. Jude Donor '11-'12-'13-'14-'15
Did it start right after changing the plugs and wires? Or did you change them as a result of the problem? It could be a loose plug wire.
I'm trying to think what would affect the engine in that way and not cause a code. The only thing I can think of is an isolated problem (isolated to one cylinder). Valve train, injector, a bad coil. You could start pulling plug wires one at a time to see if indeed it is isolated to one cylinder.
“you need to check the plugs. The stock platinum "pucks" come off and the gap opens up and can cause a rough idle. very common problem with the ac-delco platinums. A good amount of rough idling problems can be tracked to ignition systems. When both my C5's were new they still didnt idle smooth as glass. A slight amount can be expected due to the cam profile. Even stock its fairly agressive compared to previous generations.”
You could have an air leak around the MAF and clean the MAF with CRC MAF cleaner if it looks discolored, check your PCV valve and it’s connections too.
This guy had the same problem and it was his engine coolant sensor connection…
http://forums.corvetteforum.com/show...ent+rough+idle
Well at this will keep you busy!
I'm trying to think what would affect the engine in that way and not cause a code. The only thing I can think of is an isolated problem (isolated to one cylinder). Valve train, injector, a bad coil. You could start pulling plug wires one at a time to see if indeed it is isolated to one cylinder.
“you need to check the plugs. The stock platinum "pucks" come off and the gap opens up and can cause a rough idle. very common problem with the ac-delco platinums. A good amount of rough idling problems can be tracked to ignition systems. When both my C5's were new they still didnt idle smooth as glass. A slight amount can be expected due to the cam profile. Even stock its fairly agressive compared to previous generations.”
You could have an air leak around the MAF and clean the MAF with CRC MAF cleaner if it looks discolored, check your PCV valve and it’s connections too.
This guy had the same problem and it was his engine coolant sensor connection…
http://forums.corvetteforum.com/show...ent+rough+idle
Well at this will keep you busy!
Pro
Joined: Apr 2006
Posts: 552
Likes: 0
From: Alton Illinois
i had a non corvette do this once and it turned out to be a coil pack. similar symptoms. looks like the shotgun approach! maybe this may be a dealer trip. deep pockets?
how about getting an engine analyzer hooked up at a shop and see what it says? with on board computers i dont know if they exist anymore. a tuner may be able to get readings that will help. i sure am thinking ignition.
jim
how about getting an engine analyzer hooked up at a shop and see what it says? with on board computers i dont know if they exist anymore. a tuner may be able to get readings that will help. i sure am thinking ignition.
jim
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
Ive seen MAFs act really strange like this before.
Check the spark output on both banks and make sure that your getting a nice hot spark. Make sure to check both sides. Insert a phillips screwdriver in the boot end and use a second screwdriver that is grounded to form a gap that you can vary. Should be able to jump a good 1/4-3/8" and be a blue color.
Check the spark output on both banks and make sure that your getting a nice hot spark. Make sure to check both sides. Insert a phillips screwdriver in the boot end and use a second screwdriver that is grounded to form a gap that you can vary. Should be able to jump a good 1/4-3/8" and be a blue color.
Drifting
Joined: May 2003
Posts: 1,715
Likes: 1
From: cAshburn VA
