90 s10 blazer 4.3L stalling, erratic idle.. please help!

[gunner0352]

I thought at first that i ran the fuel too low and clogged up the fuel filter with crap from the tank. I've pulled it off and checked it and it seems fine. now everything i see is somewhat vague.. "MAP sensore, MAF sensor, TPS, Dirty Throttle body"..

it starts fine, but will not idle. even if i give it a little gas and hold it stable, the RPMs are erratic, up and down. if i give too much gas too fast, it bogs down. If i let off the gas, the idle drops to stall. If i "feather" the accelerator, i can get it up to higher RPMs, but it will sputter a bit and start dropping.

Please someone give me a more certain answer, I dont have the money to guess my way through this. Thanks

[gunner0352]

ok I measured the TPS with an ohmmeter. Pins A to B at rest measure 1.7k, wide open measures about 5.6k. Then from B to C measures just the opposite. at rest it measures 5.6k, wide open measures 1.7k. does this sound right? i started it without reconnecting the TPS. didnt seem to make much difference at all. still erratic up and down idle.

So i reconnected the TPS, DIS connected the MAP sensor and started it. it actually ran smooth and stable for a short while. even through reving. Short lived though. After reving, it started dropping the idle again and would go almost dead, then back up smooth, then back down again.. so on. Also the check engine light came on, which im sure it should with the map disconnected. no light with everything connected though. I assume that means it could still screw up as long as its within range of spec.

Im not sure how to test the MAP. Any ideas? this is my only transpo and i have very little money and a 7 yo to get around. so any help would be gretly ppreciated. thanks

[gunner0352]

ok, i was really hoping for some kind of answers. any direction would help. someone had to have seen this or had it happen before.

So I went out last night and just bought a MAP sensor. No luck. more searching today and found out how to short the ecm to read the codes. Initially there was a code for low MAP and a code for low TPS. but that came from me disconnecting them and starting the truck. So i reset the ECM, started the truck again.. same symptoms. then rechecked the codes. only code 12 now that i reset it.

So, someone please tell me, what causes these symptoms and does not throw a code? Im in desperate need of help here. its my only way to get me and my son around. And as i stated before, I dont have the money for a shop, or to just guess my way through a bunch of new parts i dont need.

Please help if you can. Thanks

[exalteduser]

Try and check your vacuum. look at all lines for cracks or unplugged lines.
i think the parts store will rent out a gage to check your vacuum too.

[Gabe25]

What type of fuel delivery do you have (Eight didget of VIN)? Throttle Body or Fuel injected? What is your fuel pressure reading?

[gunner0352]

Thanks for the response. A visual inspection of the vaccum looks ok. the lines dont look cracked or worn, and everything seems to be connected.

Its a TBI, vin "Z"

Also not sure if it could be related, but it would puff blue smoke after being warm then sitting for 15 minutes or so. Like a trip to the store. When I start it up to go home it would blow out smoke for a few seconds then ease up. Maybe the vavles are coated? could maybe be a symtom of smoke and stalling right?

[gunner0352]

Well, I finally gave up and took it to the shop. $400 later, it was the fuel pump. Apparently not all the way dead. 18 lbs one minute, 0 the next. that certainly explains the erratic idle.

So, thank you all for your help. and i hope this helps someone else to save a little money before buying all the little parts and guessing.