Engine Please help, rpm surge when shifting

AbhorrentSpecies · Apr 11, 2024

Been a while since I've been on here. Anyway, I can't take it anymore. I've tried everything I know. I have a stock 89 GT. Only headers and x pipe. Not Everytime but almost, when I start the car it almost dies and recovers. It's done that ever since I bought the car. Over the last 6 months it started to develop a rough idle so did I base idle reset and now it surges like 400 rpms Everytime I shift. So now I have all three symptoms. Almost dies and recovers upon start up, idles rough and surges when shifting. I feel like I've checked everything but I'm obviously missing something. Any help is greatly appreciated.

limp · Apr 11, 2024

Check for vacuum leaks??
ECU need rebuilding?

AbhorrentSpecies · Apr 11, 2024

limp said:
Check for vacuum leaks??
ECU need rebuilding?

Yeah, no vacuum leaks, new ect, act, new IAC, new timing chain, new EGR, tps set to .96 and climbs normally to 4.6 volts, 10 degrees initial timing. I'd like to rule out anything else before the computer, since rebuilding ecu will have my car out of commission for weeks.

AbhorrentSpecies · Apr 11, 2024

AbhorrentSpecies said:
Yeah, no vacuum leaks, new ect, act, new IAC, new timing chain, new EGR, tps set to .96 and climbs normally to 4.6 volts, 10 degrees initial timing. I'd like to rule out anything else before the computer, since rebuilding ecu will have my car out of commission for weeks.

limp said:
Check for vacuum leaks??
ECU need rebuilding?

I read somewhere that the tps can cause these problems though it seems to be functioning normally. One thing I did notice is if I try to read the tps at idle with the car running, the voltage is all over the place.

AbhorrentSpecies · Apr 11, 2024

AbhorrentSpecies said:
Yeah, no vacuum leaks, new ect, act, new IAC, new timing chain, new EGR, tps set to .96 and climbs normally to 4.6 volts, 10 degrees initial timing. I'd like to rule out anything else before the computer, since rebuilding ecu will have my car out of commission for weeks.

So I just noticed something. Someone said to check tps voltage at the black and green wire, not ground to green and it jumps all over the damn place. Even when I tap the orange and black it shows 5 volts for a second and then starts bouncing all over. Is that just a bad tps sensor or something more serious?

AeroCoupe · Apr 11, 2024

Check the 5 volt reference wire (orange/white) at the EGR with the TPS unplugged and see if it does the same thing. If it fluctuates then it could be the ECU. If not then my guess would be the TPS but I would think you would get a code for it. With that said have you pulled codes i.e. KOEO codes?

AbhorrentSpecies · Apr 11, 2024

AeroCoupe said:
Check the 5 volt reference wire (orange/white) at the EGR with the TPS unplugged and see if it does the same thing. If it fluctuates then it could be the ECU. If not then my guess would be the TPS but I would think you would get a code for it. With that said have you pulled codes i.e. KOEO codes?

I actually just checked the reference wire with it unplugged and it stays completely steady at 5.04 volts. Only when I try black to green or black to orange at the actual sensor does it fluctuate all over. No codes at all other than for smog pump stuff, which i don't have.

AeroCoupe · Apr 11, 2024

I would say bad TPS.

AbhorrentSpecies · Apr 11, 2024

AeroCoupe said:
Check the 5 volt reference wire (orange/white) at the EGR with the TPS unplugged and see if it does the same thing. If it fluctuates then it could be the ECU. If not then my guess would be the TPS but I would think you would get a code for it. With that said have you pulled codes i.e. KOEO codes?

Oh sorry, you said at the EGR, okay. Lemme do that. I just checked the constant inside the harness with the TPS unplugged.

Engine Please help, rpm surge when shifting

AbhorrentSpecies

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limp

wrap a little cheese around it and its a done

AbhorrentSpecies

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AbhorrentSpecies

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AbhorrentSpecies

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AeroCoupe

lube between the nut and the face. I know my lubes

AbhorrentSpecies

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AeroCoupe

lube between the nut and the face. I know my lubes

AbhorrentSpecies

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Engine Please help, rpm surge when shifting

Active Member

wrap a little cheese around it and its a done

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Active Member

lube between the nut and the face. I know my lubes

Active Member

lube between the nut and the face. I know my lubes

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