I did some research and this guy was about all i could find with the same issue/blazer. TOPIC: https://blazerforum.com/forum/2nd-ge...reverse-12340/

My Blazer likes to stall out and drop in rpms [100-200 rpms] after being put into reverse or drive. It will sometimes catch itself and stay running, but more than half the time it stalls and i have to restart it. sometimes its fine, others its not. I noticed the past few mornings, its been bad, but during the day you dont see a big issue with it. but its becoming an issue in traffic cus it will do it in the middle of traffic if stopping at a red light or stop sign.

I recently put in a new air check valve, new elbow from the check valve, wrapped it with thermal tape, replaced the t that connect the check valve/air pump... i still had a slight idle issue, so i went out bought a new IAC and it was still stalling out, so i went and got a new TPS because i found it was throwing a code for the sensor. and the idle still seems to be somewhat funny? Also notice my oil pressur gauge plays tag with the rpms.. when my rpms drop, the oil pressure drops, and when the rpms are higher, the oil pressure is higher.. I'm out of ideas and need to get this issue fixed as its my only transportation. Thanks in advance!

 

did this problem occur with the ac on? my 2002 will stall like that if i shut the engine off with out shutting the ac. off and letting all the air run out of the vacuum system for ac.

as for your oil pressure, it isn't as much when idling low like that.
you could try cleaning your throttle body and making sure you have enough fuel pressure.

 

Nope was just doing it to do it. It's random really

And I've cleaned the tb a couple times and where is the fuel valve on the fuel rail? Can't find it nowhere lol

 

behind the intake plenum next to the distributor is where the test port is. should have about 60 to 65 psi.

 

Pressure is good, right around 62. It's doing it pretty much for the first 20 minutes the car runs. Then it'll drive dine, til you shut it off for about a half hour. Go to start it, it'll do it, again.

 

I had this issue and it was the iac. Strange. I do remember some research i found that some of the pintles on the iacs on aftermarkets are shaped a bit differently some can cause strange idling issues issues. At least on the 1st gens. where did you get yours from? Mine would stall if i slap on the gas for a quick sec while in reverse. It still stumbles a bit if i do it now,even though it never stalls anymore.

 

Have you tried unplugging the MAF sensor to see if it helps? If it does then clean it with MAF sensor spray only.
Edit: what was your 10 minute later number for your fuel pressure. It should be inital 60 to 65 and not go below 55 for 10 minutes. That is wiith the key on and engine off.

 

Its an AC Delco IAC; costing a grand total of $62.?? figured something that deals with the electrical of the engine, i should go with brand new instead of a junk yard part. My brother was unsure but said it could be doing this due to the new sensors and the computer needing to configure them or something of the sort?

I have unplugged it but it just dips slightly in RPMs and stays running. Haven't tried running it with it unplugged tho, should i give that a go and see how she does? If it runs better, could it be a bad MAF or just need cleaning?
As for the pressure test, I'll have to redo it tomorrow as I gave the tester back to my buddy. If the number drops to 55 or lower, would it be safe to say it could be a fuel pump issue?

 

Yeah try to drive it with it unplugged. If it gets better then clean it.

 

Cleaned the MAF. Went back to Autozone after about a week of the stalling and swapped out the brand new iac and tps, with both a new iac and tps but its still stalling and having an off idle. My buddies dad told me after I swap it, drive the car for 10 minutes going 50+ I did that for a half hour through Detroit but it didn't help. Lol It'll do it for the first 10 minutes of driving then stop. I noticed while driving around 45mph it'll be at or close to 2500rpms, and as soon as I let off the gas, it automatically drops a 1k rpms which is how I.know when it will stall. Trying to get.this issue solved before snow hits us.. stalling coming to a stop in ice, would be bad. Any info would be grateful!