High RPM idle at starting

cruiser54 said:

Good chance your Throttle Position Sensor is bad.

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Talyn said:

This.

Or a possible vacuum leak.

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cruiser54 said:

REnix seems to respond differently to vacuum leaks than the later models for some reason.

That said, it's always a good idea to check the intake manifold bolts and be sure they haven't loosened up.

Very typical on Renix to have intermittent idle flare due to 2 things. Numero uno is bad TPS, but it can also be poor grounding of a circuit that is shared by MAP, CTS, IAT, and the TPS itself. See post 5 in my link to diagnose that.

Another area of high resistance essing with the same sensor ground circuit is the c101 connector. See posts 2 and 27.

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8Mud said:

Like Cruiser said and....

Water in the TPS will do that. If you have washed your motor lately, you may want to replace the TPS or maybe try drying it out. I set one on the heater in my living room and left it there for a week after a soaking and it was good again. 2500 RPM idle is most often a wet TPS or a fairly large vacuum leak.

I had an occasional high idle flair (hot start) on mine, it went away after I fund a loose ground splice in the harness. You may want to shake your harness around some and see what happens. Mine was under the tape in injector harness where it makes the bend about 10-15 cm towards the drivers side. Mine was more an erratic idle, sometimes high, sometimes low with the bad splice, but would occasionally go up to around 1500 or so.

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