TPS Problem

[Maupins]

Well I am having an issue with my truck, it's a 96 S-10, 67k, v-6, 2wd with AC. I have a W engine.

I was having a lot of problems, loping and dieseling when you would turn it off and when you were in park or neutral the RPMs would run in the 2k-3k range. Sometimes when driving without even touching the gas it would get up to 25mph with no signs of slowing down.

I was getting three codes, a TPS, EGR and Camshaft sensor.

I have replaced:

IAC (Idle air control) valve
TPS Sensor (three times)
EGR valve
PCV valve
IAT sensor
Coolant Temp Sensor

I have new plugs, wires, rotor and cap that I am going to go ahead and replace this weekend.

All of the trouble codes are gone but the TPS, and I have changed the sensor twice thinking I might have gotten a bad one. Now right before I changed it (the TPS) it was running great, no SES light and it was driving perfect. Then the SES light comes on and now it's shifting real hard out of first, and it won't shift untill the RPMs are around 2500, after that it shifts normal. I think that this is some kind of electrical problems related to the TPS, because when the SES light is off it runs and shifts normal. I can't figure out the TPS fault though, I am pretty sure that it's not the sensor itself and I am starting to suspect the connector. I have checked it with a voltmeter and it reads 4.9vdc, but I don't know how to check it when it's hooked to the sensor. At this point I am stumped and don't know what to try or where to go from here. Any help would be appreciated.

Thanks
Steve

[j cAT]

with a vacuum guage check all vacuum lines.....all intake vacuum ports must have a good vacuum .....the firewall area is were I have found bad hoses...if the hoses have cracks buy a good amount of hose and replace all....when a vehicle is 10 or more years old it is time to replace these rubber parts....also check lines that go under the vehicle transmission area as well....

[MT-2500]

Sensor hooked up key on.
Probe the wires at sensor plug in.
Black wire is ground check for good ground.
Gray wire is 5 volt reference. check for 4.6 -5.0 volts
Dark blue is voltage reading to computer.
Should be .50 to .85 volts in idle position and should swing even with no drop outs to 4.6 to 5.0 volts wide open throttle.
And if you have a good scanner you can read TPS voltage in computer.
Should read .50-.85 volts idle and swing to 4.6. 5.0 volts wide open throttle.

What code no were you getting?
Good Luck

[Maupins]

I am getting code PO122. I got a new connector today from chevy, $48 bucks later... so I am going to test and replace the one on there now, I have had a lot of people telling me that the connectors are a common fault point.

MT-2500: just a quick question, and I feel pretty dumb asking, but how do you probe the connector with it hooked up? do I stick the probes through the soft rubber on top of the connector (where the wires are going through) and where are the vacuum hoses, what do they look like? I can't find anything showing a diagram of where they are run. I know that is going to make me sound like I don't know what I am doing, but I do know how to turn a wrench, it's just that it has mostly been on old VW bug's.

[manicmechanix]

Originally Posted by Maupins

MT-2500: just a quick question, and I feel pretty dumb asking, but how do you probe the connector with it hooked up? do I stick the probes through the soft rubber on top of the connector (where the wires are going through) and where are the vacuum hoses, what do they look like? I can't find anything showing a diagram of where they are run. I know that is going to make me sound like I don't know what I am doing, but I do know how to turn a wrench, it's just that it has mostly been on old VW bug's.

MT-2500 sounds like he knows what he's talking about, but I'll try to help you. For testing the TPS while connected you backprobe the connector where the wires go into the rubber part on the back of the connector. Use a straight pin to careful make contact.

As far as the vacuum hoses, and it really sounds like you might have a vaccuum leak, you look for any rubber or plastic hoses running to your manifold. There should be a sticker in the engine comaprtment showing your vaccuum hose routing. You shouldn't have that many-a big one going to your power brake booster, one to your map sensor, a PCV valve hose and an EVAP hose and maybe one running to your Hvac. I would think this truck has electronic EGR but if not check that hose too if it has one (I doubt it does).

[MT-2500]

Code 122 is low voltage.
As said you will need to probe the wires.
Or Some use a bed of nails probe.
Which LEAVES SELF HEALING HOLES.
When probing always seal the hole back up with sealer when done checking.
If you do not find the problem atps plug in.
Also check where the wires go into computer and get a scanneron it and see what the compurter TPS readings are.
Good Luck

[Maupins]

Well after replacing the following:

IAC (Idle air control) valve
TPS Sensor (three times)
EGR valve
PCV valve
IAT sensor
Coolant Temp Sensor
Vacuum hoses
TPS Sensor connector

And I have new plugs, wires, rotor and cap that I am going to go ahead and replace this weekend.

I finally fixed everything and I think that it all came down to the TPS Sensor connector, a $45 piece of plastic (GM#88988301), so now everything is running great, the tranny is shifting smooth and normal, and it's running great.

Thanks to everyone for all of the great info and help, the manuals will only get you so far, it's nice to have someone give you some not so technical and clinical advice.

Thanks again

Steve

[MT-2500]

You are welcome.
And thanks for posting back how it went.
Glad you found the problem and got it fixed.