cam3.4aro

Here is the problem:

My car idles at 1000RPM up to 3200RPM, depending on how it feels a certain day! Everytime I reset the PCM it will immediately go back to its normal idle speed. But the next time I start my car...wooooosh! The rpms rocket unless i reset the PCM each time. I have reset it by pulling of the pos. and neg. off the battery, but recently ive just been pulling the PCM fuses in the driverside dash. Im not sure if the 17 degree weather has anything to do with it, but it does tend to do this almost every winter...this winter has been the worst.

There have also been times when I've driven it at the high idle speed and after about 20 miles it will lower some, but still not the normal rpm.

- I have replaced my IAC.
- I have cleaned out the housing for it and the whole intake arm (and filter) with TB cleaner. its clean as a whistle.
- Ive put in fuel injector cleaner (TL3 cleaner)

I know the next thing to do is check the voltages across the sensors...but my multimeter broke due to the cold weather
I have not sprayed the intake manifold or vacuum hoses with soapy water yet because im not sure where to spray it at. Any ideas? Possible pictures?

One more thing... If the car is running and a sensor is disconnected, will that blow up the PCM? Im thinking my dad pulled the IAC sensor...or the TPS, not sure which.

sorry about the long post. Hopefully I gave enough info

CLEAR

i had the same problem. it really really sucked. my problem lasted for several weeks. by the end my car idled at 4k so i was constantly smoking the clutch. anyways i checked the computer codes several times and it was always air management. i replaced the iac and 3 other sensors. eveytime i replaced one it would run fine for a little bit but by the next day be ****ed up again. this problem gave me the biggest headache ever. i took it to a shop and he had it for two days and couldnt figure it out. then i finally took it to chevy. they had it overnight. both places i took it to thought the throttle plate was gunked up and sticking open even though i told them i had cleaned it....both shops took the tb off and had to wait a day to get a gasket since no one in town had it. chevrolet finally fixed it. somewhere from the computer to the sensor the wires were frayed. chevy charges me about $240 to basically tape up the wires. that plus the sensors i bought put me over the $400 mark. i suggest buying a nice volt meter and a chiltons manual. you probably can fix it yourself for $100 and have a book and a tool for future use.

cam3.4aro

Well, I finally went to Auto Zone to buy a new digital multimeter and checked the resistance across the IAC. It read about 55ohms on both sets of pins. So I know thats not the problem. I had my car scanned with an off the shelf code scanner and nothing showed.

While there I did find out how much a new PCM is - $99.00 with a core return, which they said is worth $145.00. Once you buy it theres no returning it they said. So that would definately be a last choice solution.

I guess the next thing to do is start back tracking the wires from the IAC and TPS sensors and look for faulty wires.

fbird95

Idle control module. Thats my thought, a lot of times it doesnt through a code for a long time

cam3.4aro

Just an update, i'm still having the problem..especially with the weather changes. lol. winter to spring and so on.

GRNcamaro

im not a 100% sure of this so dont jump down my throught if there isnt one but i imagine there must be. you should try checking your throtal positioning senson.

MustangEater82

right behind the throttlebody there is t-fitting. That t-fitting has been known to commonly crack and cause a vacuum leak. My 3.4L leaked there. GM only sold a the entire vacuum lines for the motor.

I doubt that is your problem, since its fine when you reset your computer but worth checking.

HBHRacing

IAC will not cause idle in excess of over 2000 RPM. Stuck throttle cables, throttle blades, or vacuum leaks will. My money is on the vacuum leak.

cam3.4aro

Still havent done a thorough check for vacuum leak. Right now I'm concentrating on replacing the switch connected to the Multi-Use Arm on the steering column. Right now I have everything off past the blinker assembly... Im missing some star bits to take of a piece of the actual column to get the small multi-use arm switch off of the left side of the column. ugh. After that, Ill start looking for vacuum leaks again.

btw, you'll notice the start date of this subject and the latest post for this is about 2 years apart.... My idle problem doesnt happen every day, so I'm not in a rush to fix it. However, the continuing pleasant weather has been persuading me to work more on my car....in addition to my huge tax refund..the first time my parents havent claimed me.. lol.

cam3.4aro

Since this spring, I have not had any idle problems. I was going to spend 2 days fixing vacuum hoses and any part that may cause a leak, but my freakin starter took a $h!# on me and had to replace it.... boy was that a b!#c# . Eventually I got the old one out and the new one in using the "force" method...crow bar pivot on the exhaust and man-handle the starter, LOL.

Now I just need to take off another weekend and see if I can get these vacuum hoses and possibly that T-fitting replaced. Crossing my fingers hoping nothing else craps out on me in the meanwhile.