My question exactly Patrick. I’m getting a different voltmeter and trying again. I’m gettin crazy readings off the battery as well. I’ll keep you posted.
My question exactly Patrick. I’m getting a different voltmeter and trying again. I’m gettin crazy readings off the battery as well. I’ll keep you posted.
TPS is getting 15+ V? If true, ECM is likely dead.
All ECM sensors 5v, ground and signal direct from ECM. Except O2 that generates 0-1V
Even if something shorted to "12v" from battery and alt side, ECM is likely dead now even if seems to work in other ways.
------------------ Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should. (Jurassic Park)
Old multi meter was bad. I'm getting 5 volts now so my ECM seems to be alright. I do need to change out the TPS. When I tested the signal there was not change as I increased the throttle position. Hopefully that fixes my high idle. Baby steps. Thanks for the input. It is appreciated.
The wire with 5 volts won’t change with throttle movement. There are 3 wires. 5 volt, ground and signal. Only the signal wire will change readings when throttle is opened. Should read around 0.5 volts closed, and over 4 volts wide open. Look for smooth increase in signal voltage as throttle is opened. This is where a graphing meter is nice.
------------------ 10.007 @ 135.54MPH. <-- Video Best 60' 1.42 Best mph 138.82 Billet 6262 Precision turbo, PT1001 intercooler, ST1 cam, 140lb springs, comp pushrods, HV3, stock L32 bottom end and heads.
Old M90 XP Cam time - 11.425 @115.60 1.543 60'
[This message has been edited by LFiero67 (edited 04-25-2023).]
Old multi meter was bad. I'm getting 5 volts now so my ECM seems to be alright. I do need to change out the TPS. When I tested the signal there was not change as I increased the throttle position. Hopefully that fixes my high idle. Baby steps. Thanks for the input. It is appreciated.
The TPS doesn't cause a high idle. That's usually a vacuum leak or bad idle air control(IAC) valve.
As LFiero67 stated. the signal wire should read from .5V to over 4V at WOT.
i have replaced tps, iac ect among egr, chasing a erratic up and down idle. i had old always charging battery so replaced today, thinking maybe not getting good voltage. it finally went down and stayed at 110 rpm for a little while, but then went back to 2400rpm and gradually came down and low enough that it killed. did a new code check and it showed a 02 error, and continued to say check TPS for mal aligned adjustment. could a bad o2 sensor be screwing up the TPS ? curious why 02 sensor code would include this about TPS in the same sentence ? BTW 87 GT 2.8 any help would be good ! thank you
Adding a question off the original topic is considered somewhat rude. You should start a new topic with your question. Anyway, the ECM in the Fiero is programmed to have a rather high idle after it is first connected to the battery. So yes, replacing the battery will make your Fiero idle rather fast on the first start-up, assuming you let it run long enough to get to the slow idle. If not the second and additional start-ups will be at a rather high idle until the ECM learns the engine. If you have additional questions, you do need to start your own thread.
sorry for piggybacking this post. also thanks for your reply. what about the code description showing o2 sensor and check tps for adjustment ? are the 2 related ? thanks again
