Idle surge
Idle surge Got a 98 Camaro Z has heads and Cam. Added a 90mm Fast intake and 90 mm FRE Throttle Body. Got it tune and car runs excellent and makes power. But after couple of months later developed a idle surge does it evertytime I start the car and it idle surges either if its cold or hot outside and even with the engine warmed up. Swapped out Throttle body with a PTM 90mm and idle surge still there. Tried and replaced IAC motor and TPS sensor too and nothing. HAVE a SES light on. Have a MAF code for low input. So I chnged out the MAF for another stock MAF. Problem still there. I need to try to disconnect battery and reset PCM. To see if thats going to help my problem. You guys got any thought or ideas? Any expierence this same problem before?
I have already looked for Vacuum Leaks didn't find any. But I don't know if my MAP sensor bad. Check it out yesterday was covered with a little bit of oil but I have a catch can on the car. I"M STUMPED! And Idle surge is driving me crazy!
PLEASE HELP!
I have already looked for Vacuum Leaks didn't find any. But I don't know if my MAP sensor bad. Check it out yesterday was covered with a little bit of oil but I have a catch can on the car. I"M STUMPED! And Idle surge is driving me crazy!
PLEASE HELP!
I've found my idle surging to be mostly fuel related. Too rich
and the motor reacts too slowly to incremental IAC air and
the whole system goes unstable.
If unplugging the IAC makes idle stable than this is probably
the deal. Then the question is, why rich a month later? A
vacuum leak on a single cylinder (manifold seals, retorque?)
would put 7 of 8 rich, etc. Note that old-school vac leak
methods don't work so well when you have a live IAC that
tries to fight any change in RPM. Unplugging or locking the
IAC (scan tool) will make any response to carb cleaner or
propane a lot more observable.
I have seen something that seems like "fuel surge" as well,
which I think relates to the slope of the VE tqable in the
MAP dimension. Like excess MAP makes additional air mass
error and overfuels (not properly-fuels).
If your SES codes have faulted you into open loop then
you may have this coming from the open loop fuel-air
table as well, commanding additional enrichment just
because MAP is higher (and more MAP making more
fuel, makes the motor even more soggy and MAP comes
up some more, etc.).
You would like to have some scan tool to observe what
all is going on.
and the motor reacts too slowly to incremental IAC air and
the whole system goes unstable.
If unplugging the IAC makes idle stable than this is probably
the deal. Then the question is, why rich a month later? A
vacuum leak on a single cylinder (manifold seals, retorque?)
would put 7 of 8 rich, etc. Note that old-school vac leak
methods don't work so well when you have a live IAC that
tries to fight any change in RPM. Unplugging or locking the
IAC (scan tool) will make any response to carb cleaner or
propane a lot more observable.
I have seen something that seems like "fuel surge" as well,
which I think relates to the slope of the VE tqable in the
MAP dimension. Like excess MAP makes additional air mass
error and overfuels (not properly-fuels).
If your SES codes have faulted you into open loop then
you may have this coming from the open loop fuel-air
table as well, commanding additional enrichment just
because MAP is higher (and more MAP making more
fuel, makes the motor even more soggy and MAP comes
up some more, etc.).
You would like to have some scan tool to observe what
all is going on.
If the MAF code is still there, the PCM is defaulting to the VE table (which if not tuned for your current combo may cause the surging). If changing the MAF didn't fix it, then your code may be the result of a poor electrical connection or a bad ground. Do a voltage drop test on the ground wire...should be less than 50 millivolts with Key On/Engine Off. Power should be 12V or higher, and MAF frequency should be 2600 Hz or higher on most cars. As was recommended above, perform a data log to see what the MAF frequency is at, and use a good ol' multi-meter to test power and ground.
I already changed out the IAC, TPS and MAF sensors. NO MORE SES light on and no more MAF Codes. Set TPS voltage at idle at .60 volts. Thats what its supposed to be at. Also disconnected battery car seem to have fixed the idle surge for a day only. Car idle normally and ran as it always has. Then the next day the idle surge came back. as I started the car and let it warm up.
I did notice the MAP sensor a bit loose the orange rubber seal that seals it up on the intake is all worn out on mine. The orange rubber seal is worn out and real thin. Could that be my problem? I tried replacing it but can't seem to find a replacement for it. Anyone know where to get one?
After disconnecting battery car idle fine for a day then the next day it was back to Idle surge.
I did notice the MAP sensor a bit loose the orange rubber seal that seals it up on the intake is all worn out on mine. The orange rubber seal is worn out and real thin. Could that be my problem? I tried replacing it but can't seem to find a replacement for it. Anyone know where to get one?
After disconnecting battery car idle fine for a day then the next day it was back to Idle surge.
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Might be some mistrimming at idle, pushing the
idle AFR rich over time and the resets give you
back clean running until the trims wind up again.
Could try pushing the O2 sensor switchpoints at
the lower Airflow Mode cells, like 200mV at the
lower end, do things to heat up the sensors
better, etc.
idle AFR rich over time and the resets give you
back clean running until the trims wind up again.
Could try pushing the O2 sensor switchpoints at
the lower Airflow Mode cells, like 200mV at the
lower end, do things to heat up the sensors
better, etc.
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TECH Regular
Joined: Apr 2004
Posts: 470
Likes: 0
From: Norman, OK
Anyone ever fix this? I've got the same problem. All the sudden, idle surging. The only change was the car sat for a long time and completely drained the battery. Now I can't get this crap to go away. The only thing I can think of is a vacuum leak, I haven't check for one yet...
TECH Fanatic
Joined: Aug 2005
Posts: 1,691
Likes: 1
From: Sunny London, UK
Usually most blokes are in closed loop at idle, so there is not much you can do about fueling.
In which case you are left with airflow and spark timing.
Now if nothing has changed the most likely issue is your IAC isnt moving nicely, perhaps its got gunk in it and needs a clean etc.
Otherwise usually less timing is better than more at idle. Also its better to have slightly more idle airflow in my experience than less.
When all seems lost a return to stock values and following the latest recommended idle tune process is often a good idea as after months of "minor" tweaks you can find yourself miles off base.
... at least thats what Ive found over time.
In which case you are left with airflow and spark timing.
Now if nothing has changed the most likely issue is your IAC isnt moving nicely, perhaps its got gunk in it and needs a clean etc.
Otherwise usually less timing is better than more at idle. Also its better to have slightly more idle airflow in my experience than less.
When all seems lost a return to stock values and following the latest recommended idle tune process is often a good idea as after months of "minor" tweaks you can find yourself miles off base.
... at least thats what Ive found over time.
