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rough idle

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aussie

Guest
my 86 has a rough idle not to bad but annoying.have changed plugs,leads both fuel tank filters but has not eased the problem.it does not affect the running at normal speeds and even on cold starts seems to idle sweet until it comes of cold start mode.any help or input would be greatly appreciated.
 

jeepie

Well-known member
Joined
Feb 6, 2002
Messages
162
Location
Dunmore, Pa.
Corvette
1991 Coupe Blk/Blk
Mine had a rough idle also, I cleaned the TB and changed the plug wires, seems fine now. I am not sure which thing helped the idle, but I did find that one of the plug wires was cut where it went behind the engine, so I am guessing that was a lot of the problem. I believe it was plug wire #7.
Good luck.
 

69MyWay

Well-known member
Joined
Jul 3, 2001
Messages
4,364
Location
Auburndale, Florida
Corvette
1969 Killer Shark
If all else fails, check out the EGR valve. You can have a bad/leaking valve that does not show up on a diagnostic scan. The G.M. service manual provides an excellent section on trouble shooting it.

It it is the EGR, it will only get worse over time. Other than that I would think you could have some dirty injectors. Get them cleaned, then look into the EGR if it continues.
 

GiDvEtTe84

Well-known member
Joined
May 8, 2001
Messages
67
Location
Maurice, LA
Corvette
1984 Cross-fire Corvette Coupe
Try checking the distributor cap and rotor. See how fouled it is.
 

cantdrive55

Member
Joined
Jan 9, 2009
Messages
5
Location
Miami
Corvette
1990 Pimpmobile
Unlucky # 7

Mine had a rough idle also, I cleaned the TB and changed the plug wires, seems fine now. I am not sure which thing helped the idle, but I did find that one of the plug wires was cut where it went behind the engine, so I am guessing that was a lot of the problem. I believe it was plug wire #7.
Good luck.


Thats funny - with my rough idle prob the 7 cylinder was misfiring - did a tune up and found the darn plug was broke in half - and the whole thing was stripped where the plug goesin !

I have done a few things like tune up and TB/fuel injector cleaning - my idle still runs rough at stop signs after it warms up; gotta put the car in P or N - any suggests?
 

cantdrive55

Member
Joined
Jan 9, 2009
Messages
5
Location
Miami
Corvette
1990 Pimpmobile
I checked the cap and rotor -they were melted! - replaced those - I'm understanding my nect move should be to clean the EGR and IAC (in leau of replacing them)
 

gmjunkie

Well-known member
Joined
Nov 11, 2004
Messages
4,547
Location
Old Fort NC/Vero Beach FL
Corvette
03 Z-51,78 L82 Coupe
;shrugWhat should I troubleshoot first - the EGR or the IAC?
I'd maybe check the temp sensor in the intake,it'll sure cause one to run just like you describe!!! Yep,it's the one below the throttle body,it's a real Joy to change!!~!! :D:D:D
 

gmjunkie

Well-known member
Joined
Nov 11, 2004
Messages
4,547
Location
Old Fort NC/Vero Beach FL
Corvette
03 Z-51,78 L82 Coupe
Question: Where is the EGR Valve on '94 LT1?
At the back of the intake,large round diaphragm with a single vacuum line going to a solenoid switch under the left fuel rail cover!!:thumb:thumb:thumb
 

LT4man

Well-known member
Joined
Jun 25, 2003
Messages
2,214
Location
Chicago
Corvette
96 Collectors Edition LT4
At the back of the intake,large round diaphragm with a single vacuum line going to a solenoid switch under the left fuel rail cover!!:thumb:thumb:thumb

Is the EGR valve on an LT4 in the same place?

WHILE YOU ARE LOOKING FOR THAT, DON'T FORGET TO SAVE THE :w!
 

gmjunkie

Well-known member
Joined
Nov 11, 2004
Messages
4,547
Location
Old Fort NC/Vero Beach FL
Corvette
03 Z-51,78 L82 Coupe
Is the EGR valve on an LT4 in the same place?

WHILE YOU ARE LOOKING FOR THAT, DON'T FORGET TO SAVE THE :w!
Would be if it had one!!:boogie:boogie:boogieI ain't gonna fall for that one!!!~!!!!:D
 

LT4man

Well-known member
Joined
Jun 25, 2003
Messages
2,214
Location
Chicago
Corvette
96 Collectors Edition LT4
Would be if it had one!!:boogie:boogie:boogieI ain't gonna fall for that one!!!~!!!!:D

You must have risen early today, junk!!! :upthumbs

DID YOU AT LEAST TRY TO SAVE THE :w?
 

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