Very strange idle problem, goes away after restart

[HardWired71]

95 Jimmy SLE 4x4. Idle fine on startup cold or hot...drive it around for about 10-20 minutes or so, idle goes up. Will hold at 1k in gear 1200-1300 in park or neutral. Shut it off and immediately start it back up, idle is normal.

Cleaned EGR. Plugs wires cap and rotor were changed. Plenum gasket changed. IAC cleaned. Hooked it up to a snap-on scanner...tps reads 0% when running fine, fluctuates to 3% when it starts to act up again. Ideas? Need further info? Really at my wits end with this one.

[HardWired71]

New Code today.. P0122 Throttle/Pedal Position Sensor/Switch A Circuit Low Input

Yay.

[CanukGMC]

Originally Posted by HardWired71

New Code today.. P0122 Throttle/Pedal Position Sensor/Switch A Circuit Low Input

Yay.

Easy stuff for that one. The TPS is mounted on the throttle body (err, I'm sure it is, it is on all my other trucks, I dunno about your year). It might just be sticky or crudded up. Have you THOROUGHLY cleaned and scrubbed the throttle body with cleaner and a toothbrush? If cleaning doesn't work replace the TPS. I did it on my YJ and it was about a 10min job, I don't know about jimmy's but on my YJ the TPS was attached to the TB using tamper proof torx and I had to buy the damn bit just to remove the sensor. WHY use "tamper proof" if you can just buy the bit??? Sorry, off topic!

[HardWired71]

Changed TPS. Idle is much lower...for the most part. Now it will run correct 75% of the time instead of 25%. Turns out to be a double edged sword...computer is shot. It will start fluctuating but lower than ever before which is good. I wiggled the connectors on the computer, nothing. Rick tapped the damn thing with a pair of vice grips, 1300RPM idle. Shot right up. Time to replace the ECM. Funny thing is since he did that, it hasn't messed up once. Better safe than sorry.

[CanukGMC]

Originally Posted by HardWired71

Changed TPS. Idle is much lower...for the most part. Now it will run correct 75% of the time instead of 25%. Turns out to be a double edged sword...computer is shot. It will start fluctuating but lower than ever before which is good. I wiggled the connectors on the computer, nothing. Rick tapped the damn thing with a pair of vice grips, 1300RPM idle. Shot right up. Time to replace the ECM. Funny thing is since he did that, it hasn't messed up once. Better safe than sorry.

Yeah especially with the ECM, it probably got a small amount of himidity or moisture in there over the years and now it's shorting or has corroded up in there. When you get the new one run a line of silicone along it's edge to help keep water out for the long run, I had to do this with my YJ as well, but I consistently put my YJ up to the hood in rivers and mud holes, different useage I guess hehe

[HardWired71]

One (hopefully) last update...

It did start fluctuating again...so the day before I was supposed to go pick up a new computer I decided to look up some more prices and found a pic of my computer. Apparently there are two rows of connectors, top and bottom...this I did not know.

Went to get gas, popped the hood, pushed on the lower connectors, wiggled a little...

Fixed...2 days and over 200 miles later...the Jimmy has NEVER run this good!!! Guess one of the bottom ones was loose or something...whatever...

[HardWired71]

For those that still care...

Apparently it wasn't as fixed as I hoped...the problems did return. Same plus more throttle position intermittant voltage and low voltage codes.

I feel so stupid now that I actually found something physically wrong.

Took the computer out to clean it again, or so I thought. One of the pins on the comp was pushed in. The connector port was also screwed up. Took the computer apart, pushed the pin back through, used a pick tool on the connector...

You can actually feel the tranny shifting now...much more solid. Truck has more power too. I don't want to end it "its fixed" but after seeing something like that and being able to rectify the issue, all I can say is so far so good. Wish me luck!