So I've been having some issues with my rpm both at idle and while driving. The problems are when idling the rpm will jump up to 1500 randomly. When driving round a car park it will start jerking like it's about to stall even tho the rpm is around 1500 and cruise a a greater speed then normal. When changing gears the rpm will briefly stay at whatever it was when I clutch in before falling if I'm driving smoothly, if I'm giving it some the rpm will jump a little before slowly falling. The reason for thinking it might be a issue with the tps is I set it to halfway between .44 and .45 using a multimeter but a week later I checked again and the value had changed to .3 something. Also if it's idling high and I jiggle the lead of the tps or disconnect the tps the rpms will settle. So my question is are there any other factors that could be affecting the rpm? To be fair I drive back streets to work so I'm lucky to hit 3rd or drive in a way other then smoothly. But I wouldn't expect that to be a factor.
Sounds like you are on to something with the TPS. What does it read at full throttle? May also be worth doing a vac/boost leak test.
Check the plug and wiring to TPS as well. Its quite common for corrosion to build up on pins and wiring gets hardened with heat and time, remove boot on plug and check individual connections.
I had a similar rev up problem a while ago. No Turbo / Auto Z32 I had a split vac hose on drivers side. Skinny one that goes between the hard pipe on side of engine and plugs into intake pipe before bend to throttle. I also fixed a hole in muffler that seemed to affect my O2 sensor readings. Also check corrosion on the CAS connector while you are checking TPS connector for corrosion on pins. If you are setting TPS with plug off, you can try setting with plug on and see if any difference. I used a couple of thin dress maker pins, pushed alongside the wires into the plug so it touched the connector. I was able to clip my multimeter to the pins and get my volt reading without unplugging. I have also found that slightly too much Auto fluid seems to be offset by a lower TPS voltage.
I actually tried to buy a NEW TPS because I find my one prefers to run at 0.34 volts at idle. I was ripped off on the NEW TPS, so I am still using my original and when I checked it just then, it is still set low. It could be a combination of factors (I think too much Auto fluid) but car is running OK except for the engine oil leak. I did try setting it higher but the transmission was changing hard. Anyway getting that sorted tomorrow. Just saying that a low TPS setting does not seem to cause irregular idle speed from my example.
