OK..update. I replaced the IAC valve with a new $130 one from CarQuest (made in the USA). This valve looked IDENTICAL to the original and had more of a "thick", black, rubberized shaft behind the pintle than the cheap ($60) BWD valve I had put in a week or so ago. I tightened down the TB (real good) and replaced a worn, but not leaking, vac hose going from the PCV module connected to the intake, to a vac juction to the left of the brake fluid resevior (did this just for PM).

And the results.....drum roll please...

The truck runs PERFECT. Idles in park between 600-700rpms and in drive/gear at 650rpms. During my test drives, it seemed to result in improved power, acceleration, and stopped the "truck driving itself" problem. It also has aided in proper tranny shifting to where before it seemed to be hanging out too long in gears before shifting to the next one. My oil pressure has also dropped to around 30-35psi at idle as well.

I have noted that when starting her first thing in the morning for the past 2 days, the rpms shoot up to 2300-2500rpms and it takes a couple of minutes for them to settle back to the proper amount. Also, if I turn her off and wait 30 seconds and restart her, the truck idles down between 350-450 rpms and almost whats to stall. I attribute this to the PCM not having completely learned the proper position of the IAC for proper idle. When experiencing either of these problems, if I go ahead and drive a couple of blocks, the rpms return and stay in there normal correct range, between 600 and 650rpms. I read in an earlier post that swartlkk stated that eventually the PCM will learn the proper position for the new IAC valve at idle, but that disconnecting the battery will force the PCM to forget and relearn the correct setting. I plan on doing this tomorrow, but I feel that the problem is FIXED. Can't thank everyone enough!!! LESSON LEARNED--->Do yourself a favor...Don't get cheap parts...Proper, good quality parts really do make a difference, atleast with Blazers. I'll report back and let you know how things are going in a few days. If anyone can elaborate about disconnecting the battery and their results in regard to the IAC resetting, I'd love to hear it. Thanks again for everyone's help!

 

Some times it is the simplest things. Glad you got it figured out.

As far as the IAC position resetting on loss of battery power, that sounds perfectly normal. It is one of the learned values that resets whenever the PCM is reset such as on a prolonged (>5 minutes) loss of power.

 

Well...not sure what to think. Yesterday I disconnected the battery for 1.5 hours, connected the neg terminal back to the battery and it's still doing the same thing. I drove it around on errands all day yesterday and even let it idle for about 20 minutes before it idled down to 300rpms and shut off. Just started it a little bit ago and although it didn't start off at high rpms (2000+), when it reached 200 degrees F, it idled down, fluctuated for about 3-4 minutes between 300-450 and then it just went cu-puutt and shut off. Yesterday, after starting the truck from going in/coming out of multiple stores, it still would idle down immediately at start up and would stall when backing out of parking spaces. Again, once I drove it past 35mph, it seemed to adjust itself and drive fine. It's been 3 days now of test drives and errands and disconnecting the battery and it's still doing the same thing. Any ideas?? I noted on my reciepts that the parts I've been getting reference an engine code W for the 8th digit in the VIN. However, my Haynes book says engine W is the basic CPI when my engine is the CSEFI. Could I have gotten the wrong part. Starting to worry. Any help, ideas would be greatly appreciated.

 

Vin W is only CPI up to 95.

Have you checked the EGR valve?

 

No EGR on this 2002...remember?? Any other ideas??

 

Yeah, I forgot that I asked that above already. There are too many threads that I reply to to remember everything.

There has to be something causing the drop in RPM. The IAC should maintain idle speed at around 650RPM.

 

The IAC's are adjustable... maybe you can move the piston "in" more so that it doesn't block as much air when in the idle position. I know when I changed mine with the cheap part, it said in the chiltons to measure the original piston length and match the new one to it. I didn't touch the new one since it was almost identical.

 

The IAC is in and of itself adjustable. The PCM adjusts it to maintain idle. It should be able to compensate on its own. It's something you could try though.

 

I'll try anything at this point. I swear I eye-balled it against the one I just took out and it was at the 1 1/8" distance, but the symptoms I am having match up exactly with the valve being extended too far in to the bore. I'll try to adjust tonight and let you guys know. BTW, I am not throwing any DTC's.

 

Good and bad news for me. Good news is I got results when I screwed in/adjusted the pintle of the valve. Bad news is now I am back to idling in drive/gear at 1000-1050rpms and idling in park/neutral at 1200-1300rpms.---SIGH---What a pain. I started out with the pintle at 1 & 1/8". Manually retracted the spring and screwed in in all the way to 15/16" from the mounting surface. I guess I'll be re-adjusting in the next few days. Maybe I'll go up to an 1 & 1/16". Who new fractions of an inch could cause so many problems!! I'll say it again! WHAT A PAIN! Hey Raven, did you ever get your blazer idling down better? If I were you, I'd wait till my misery is over and I get mine "tuned-in" so that you don't have to go thru all this mess.