Have you cleaned the EGR valve?

Could have been a faulty IAC valve or it may be hanging up in the bore...

 

I didn't think 2002's had EGR valves. I'll go and check my manual, but I don't think it has one. Yea, it (new IAC valve) could be defective I suppose. I may put the ohm meter on there and test it to verify. The bore was pretty darn clean after I got done cleaning it yesterday with my tooth brush (my teeth are stained black today though. I know that everythinng seems to point to an IAC valve issue, but I've tried to make sure this part (replaced) and bore were epecially clean. Thanks for responding so quick. I'll have to wait 'till tomorrow to test IAC and unplug the vac lines. Oh...while I'm thinking of it....Is it normal for the engine to completely shut down if you take the air cleaner assembly off the top of the TB? I was trying to do some testing with the assembly off, but the engine just shut down.

 

It was sometime in mid-'02 that they went exclusively with the MFI engine. You may or may not have an EGR valve. It's worth a look.

As far as the engine shutting down when you take off the duct work, yes, that is normal. If you unplug the MAF sensor and remove it, you will be able to run the engine without it installed. But if there is no air flowing through the MAF sensor while it is still plugged in, the engine will die.

 

Ok, thanks for the tip. Yes, the engine has the CSEFI and does not have one. I almost wish it did since this would atleast be one more plausible thing to check. Thanks again.

 

OK...Update... I ran these tests about an hour after driving her to the store and back so she was still a little warm. I started by disconnecting the air cleaner assembly from the TB. I then disconnected the MAF sensor and plugged all the vac lines connected to the intake (evap. canister, pcv hose, and brake booster hose). Golf tees worked great for this. Started her up by just turning the key (no throttling) and she ran for a couple of seconds and died. Tried again and same thing and she died. On the third try, gave her some gas and she stayed running idling in park b/t 700 & 800rpms. Just for giggles (and to test IAC valve) I turned AC on and she dropped to 500rpms. I then put her in drive and she dipped to 350-400rpms for a sec and then adjusted to 500rpms. I turned AC off and she returned to 500-600rpms (still in drive). I put her back in park and she returned to 700-800rpms. I then started hooking the vac. lines back up. Brake booster hose yeilded no rpm change. Hooking the PCV hose back up bumped her up to 800-900rpms. Hooked the evap line back up and she remained at 900rpms. Put the air cleaner assembly back and when I re-connected the MAF and IAT connections, the idle jumped up to just above 1000rpms. I disconnected the IAT connection again and she slowed down a bit and then returned to b/t 900-1000rpms. I had the same results when I left the IAT connected, but disconnected the MAF. I didn't have a lot of time to single these out more since it was getting dark. It was also about 55 degrees F when I was running the test. I also think I heard a very small, but maybe could be significant, vac leak on the TB seal just below and kinda between the IAC and TPS mounting locations. I sprayed some TB cleaner and for a VERY BRIEF SECOND, it seemed as if the RPMs dropped. So I realize this could be my problem, but seems so small to be causing the problems I am having. I do find it strange that the TB only has 3 mounting bolts to the air plenum..2 bolts in front and one bolt in the rear/center. So tell me what you think. Did the RPMs act correctly??

 

Still sounds high... Hot idle speed should be ~600-700RPM.

Have you tried disconnecting the EVAP purge line and plugging the outlet on the purge valve (located right next to the coil/ICM)?

 

Where did you buy the New IAC valve or did I miss something? Is it still the ole one in your blazer ? I learned the hard way one time, I bought IAC Valve at AUTOZONE cheap(not OEM)replacement but it was faulty . Got my Money back, went to Napa bought the OEM Part from them, Bam Problem Solved. I am with Kyle, I think it to be a faulty IAC valve .

 

Yes, I bought a brand new one and installed from Advanced Auto (B&N brand I think). This was one of the parts I "threw at the problem". The old one was really gummed up after initially only half way cleaning the TB while I had it out for the IMG install. I most recently re-cleaned the TB with the new IAC valve. I think I'll replace it with an OEM replacement. On a side note, I could hear air literally racing thru the oriface/IAC passageway on top of the TB while I was doing the vac tests & I looked thru the passageway, but could not see the shaft/plunger of the IAC valve. Not sure if that helps at all. Also, I did plug the evap module outlet with a golf tee and got no change in RPM's when I re-connected the evap line back to it. Thanks again for your elp, I'll keep you posted.

Edit--ALso, Any chance the new Puralator air filter could have an affect of this magnitude and should I worry about cleaning or replacing the IAT sensor?? It seemed that this problem developed as soon as I changed the air filter (does fit perfectly) and spark plugs and wires.

 

Well, I bought a new IAC valve today...twice as expensive as the "advanced auto special cheapo". Haven't put it in yet, but I feel good about it since the retracting shaft looks bigger/thicker...more like the original one I took out. Maybe the skinnier shaft on the AAuto valve was allowing more air to entrain thru the TB, thus increasing the idle. Sounds good in theory anyway. I'll let you know whenever I can squeeze in 30 minutes between my 24hr shifts at the firehouse.

 

I have a similar problem with my 2000. For instance, on a cold start, she cranks up to about 2500-3000 RPM and sits there for a couple minutes before coming down to 1500 or so. I'll have to sit in D with the brake held tight for it to drop down to a more manageable level. Sometimes she'll idle normal after a few hours of driving and sometimes not. I too can drive up to 35MPH without touching the gas pedal.
I was concerned of a bad part, but have not gone back to change it. Some of the things I've done to try to fix this are:
Replace IAC
Replace TPS
Cleaned out TB
Cleaned out EGR
Cleaned out intake manifold completely (after replacing head gaskets and doing a valve job)

My next plan of action was to replace to fuel spider.... but since I never saw anyone report a bad part from the parts store, I never thought that could happen. (Happens on F-15's all the damn time!)
I think I might just replace the IAC again with the more quality part... and perhaps the EGR valve, since the fuel spider is quite an investment.
I'm curious to hear your results Tiregrit!