1-bad-z28

I keep getting low TP voltage codes. I already replaced the TPS. What could cause it to be low? Also, when the car has been running for about 30 mins, it starts cutting out and miss firing really bad, to the point I can't get above 20-30 mph. Today I was coming home from work and it started missing really bad like this. Then my SES light came on (low TP voltage). I could barely gain speen. It was jumping, poping, backfiring, just running like crap. Then all of a sudden it started running like nothing was ever wrong. What could possibly be the problem? Has anyone ever had this happen to them or heard about it?

shoebox

Have you checked the wiring? Monitor it with a scanner, if you can.

slopokrodrigez

Check the 5 volt reference on the gray wire as soon as you start it and after the problem shows up after it warms up.

1-bad-z28

do you think the low voltage is causing it to run like that?

1-bad-z28

there is nothing wrong with the sensor.......now what?

shoebox

Maybe you did not see my first post. Your problem seems to be intermittent. You will have to try to catch it in the act.

Injuneer

If you're sure the sensor is OK, it has to be a wiring problem. Do what Slopoke suggested. Check the continuity of all the wires, jiggling the harness and connector as you probe.

To get that code, the TPS closed throttle volts has to drop below 0.20V. If that happens, the PCM will not know you are opening the throttle, and will not know how much "power enrichment" to apply (essentially duplicating the action of an accelerator pump on a carb, by richening up the mixture when it sees the throttle snapping open).

95Chevy

I would love to know the answer to this also. I am experiencing the exact same symptoms that you described. Mine started about three weeks ago after I sprayed my engine off. It started with a high idle (2,000 RPM) and would not shift. I decided to remove my throttle body for cleaning, after I reinstalled it, the car idled and shifted perfect. The only thing now is the spitting, sputtering and back firing that starts after about 30 minutes of driving that clears up after a few minutes. During this time when the car is acting up, the car has NO power and is smoking a little from the exhaust. I changed the throttle position sensor yesterday with no change. I was leaning toward the opti, but I don't have the money to spend on it not knowing if would fix the problem.

Stoopalini

Could be the wire harness connector causing the problem. I've had two wire harness pigtails (A/C compressor & Temp Sensor) flake out on me lately.

If this is the case, it's easy to fix ... just close the gap in the pigtail with a small screwdriver/allen wrench/paperclip/etc to tighten the connection point.

If you have access to a scantool, plug it in and monitor the TPS voltage while you wiggle the connection point around; see if the voltage fluctuates while you do this.

Good luck,
Thomas.

ZMAN Z28

If you have a volt meter. I checked for volage between the grey and black wire and got 5 volts. That is the reference voltage. If you don't have 5 volts, then you will have to trace the wire to see if/where it is damaged.

To check the dark blue wire, I stuck a small guage wire in the dark blue wire connector and plugged the connector into the TPS, and hooked the lead of the volt meter to the open end of the wire. I took the other lead to any ground. I checked the voltage with the blades closed and moved the throttle to WOT. The voltage should increase from about a half a volt give or take a minor bit to about 4.5-5 volts. You will have to set the volt meter to a low value less then a 2 volt reading to get the most acurate reading.

Check the gray wire first, this will verify if you have a good reference and ground.

ZMAN