cold idle and driveability problems
Thread Starter
4th Gear
Joined: Jul 2003
Posts: 4
Likes: 0
From: tulsa ok
cold idle and driveability problems
I have an 88 vert that has developed a problem. It is a low miles
car that has been driven little (35K) and has never been a problem.
I have decided to get it out a bit more but it has suddenly developed
some problems with cold idle and drivability. Once it warms up (160
plus water temp.) it runs ok, below that it will not idle (hunts and
will eventually die) it also, if given much throttle, below the temp
where it will idle, backfires thru the intake.
I have replaced the IAC and cleaned the throttle body, and looked for
any leaks (vac, none found) but there is no change that I can see.
Has anyone seen this type of behavior with this vintage of L98?
Any course of diagnostic procedure greatly appreciated!
TIA, AL
car that has been driven little (35K) and has never been a problem.
I have decided to get it out a bit more but it has suddenly developed
some problems with cold idle and drivability. Once it warms up (160
plus water temp.) it runs ok, below that it will not idle (hunts and
will eventually die) it also, if given much throttle, below the temp
where it will idle, backfires thru the intake.
I have replaced the IAC and cleaned the throttle body, and looked for
any leaks (vac, none found) but there is no change that I can see.
Has anyone seen this type of behavior with this vintage of L98?
Any course of diagnostic procedure greatly appreciated!
TIA, AL
Racer
Joined: Aug 2004
Posts: 379
Likes: 170
From: Buffalo Grove IL
Backfires through the intake always make me think it's running lean.
I'm guessing once the system goes into closed loop mode once it warms up, the O2 sensor realizes it's running lean and richens up the mixture. That said, double-check for vacuum leaks? Perhaps a vacuum line has a leak kinda far away from the intake so it's not very easy to find?
My other guesses would be low fuel pressure, or perhaps clogged fuel injectors?
Ben
I'm guessing once the system goes into closed loop mode once it warms up, the O2 sensor realizes it's running lean and richens up the mixture. That said, double-check for vacuum leaks? Perhaps a vacuum line has a leak kinda far away from the intake so it's not very easy to find?
My other guesses would be low fuel pressure, or perhaps clogged fuel injectors?
Ben
Thread Starter
4th Gear
Joined: Jul 2003
Posts: 4
Likes: 0
From: tulsa ok
Thanks for the replies.
It is not throwing any codes.
As for the EGR, how do I tell if it is stuck?
The car certainly acts as if it is lean, I have
looked it over for vac. leaks but I know they
can be really hard to find, I may try the
propane trick. Where are the places that the
vacuum is "harvested" on this car? perhaps
I could plug them one at a time to see if that
is it?
I am thinking that fuel pressure should be around
40 psi, but I really don't know. My thinking was
if it was fuel related it would not get better once
warmed up, but I could be wrong about that!
Thanks again for the replies
Al
It is not throwing any codes.
As for the EGR, how do I tell if it is stuck?
The car certainly acts as if it is lean, I have
looked it over for vac. leaks but I know they
can be really hard to find, I may try the
propane trick. Where are the places that the
vacuum is "harvested" on this car? perhaps
I could plug them one at a time to see if that
is it?
I am thinking that fuel pressure should be around
40 psi, but I really don't know. My thinking was
if it was fuel related it would not get better once
warmed up, but I could be wrong about that!
Thanks again for the replies
Al
