Mid end problems....

[yellowoctupus]

Hey, I've got a weird problem- sometimes my truck runs perfect, good even acceleration etc, and other times it will idle and WOT fine, but anything inbetween it stumbles and sputters a lot. It seems to act up the most when I first fire it up (1st mi or two) and if it gets wet (off road etc). Is this probably a vacuum issue or electrical?? I've been hunting around and haven't found anything yet....any ideas would be great. Thanks!

 

[Tedybear]

If it gets wet....

I'd start there actually. Any humid day happen to make the problems worse?

Quick and dirty test. And it's like me---cheap.

Best done when it's dark. Have a spray bottle handy with just plain old tap water in it. Set it on "Mist" pattern. With the engine just doing an idle? Carefully spray a mist of water on each spark plug boot with the engine running. Any faults with arcing will show up pretty quick. (you'll either see it arc--hence the dark being the best time) Or you'll hear an electrical "SNAP" when it arcs. You can do the same for the disty, understandable that it is harder to give a misting to... However you'll either see/hear it arc, or you'll hear the engine start to stumble a touch.

Basic question: Last time full tune up? Plugs/Wires/Cap/Rotor? Also fuel filter and air filter?

S-

 

[yellowoctupus]

Good call on the spray test. I'll try that tonight, I remember on my old S10 before wires replacement it would arc 3" to the hood. I'll let you know how that goes. I just got the truck, so I haven't done the full blown tune up yet. Probably should...just feeling cheap at the moment.

 

[yellowoctupus]

so...I did a spray test last night and got no arcs anywhere. I misted then pretty much soaked the entire electrical system down. It ran fine, I went for a test drive, got about a mile out and it started running funny again, as if the tps wasn't registering it was even connected except at wot or closed throttle. I went through some deeper puddles (1') on my test road and it actually started running fine again????????????

 

[yellowoctupus]

Hey Teddy Bear, you wanna know what it ended up being? I have either A: a sticky IAC valve, or the ecu is just giving it weird signals. I think it might just be sticking, I have to pull it apart and clean up the valve, see how much that fixes. I unplugged the harness from it, adjusted my idle up to compensate for less air, and it runs great now.

 

[Psychopete]

Hey Teddy Bear, you wanna know what it ended up being? I have either A: a sticky IAC valve, or the ecu is just giving it weird signals. I think it might just be sticking, I have to pull it apart and clean up the valve, see how much that fixes. I unplugged the harness from it, adjusted my idle up to compensate for less air, and it runs great now.

FWIW, the screw that was adjusted is to set the base for the TPS sensor, the computer controls the idle. The screw is not a direct adjustment for the idle speed...

Pete

 

[IMenriched]

Have you checked all your ground wires. there is like 5 of them

 

[yellowoctupus]

Have you checked all your ground wires. there is like 5 of them

I think ground wires / a bad connection SOMEWHERE may have been more of my problem. I cleaned all of the connectors I could find checking for excess corrosion/dirt/loose wires, cleaned them all up, and vaselined them for future waterproofing and corrosion prevention, as well as the ground lines. I found the following grounds:

1. Back of block/head to firewall.
2. Two at the pass headlight.
3. The main one off the battery
4. more??

"FWIW, the screw that was adjusted is to set the base for the TPS sensor, the computer controls the idle. The screw is not a direct adjustment for the idle speed..."-pyschopete

How should that (tps base) screw be set correctly then (as I have re-attached my iac harness now) ?

 

[low_five]

theres one on the back of each head. pretty important cause you dont get a good ground through the head gasket to the block.

 

[yellowoctupus]

while I think I've fixed the bad ground/ dirty connectors issue I'll check for the other ground off the back of the other head. The first one was pretty dirty, and was on a dubious looking stud at best.