Cruise Control gremlins

[Montana]

My cruise control will abruptly floor the accelerator whenever engaged. It seems random at any speed, rpm or gear. It happens sometime right after engage or 5-10 min later..random. It will accel about 5-10 mph then abruptly cut accel, coast back to set speed, floor it agin, and continue doing that.

Also sometimes during idles the car revs and bounces off the idle rpm as if it senses it is about to stall and compensates for it.

I have use redline SI-1 in the tank and it runs fine otherwise.

Any ideas? The dealer wants $94 to just look at it.

 

[Kirby]

When I hear this type of problem I think ECU software, so on a hunch I checked All Data TSBs for you. Holy crap! There's like 190, and MANY are ECU software. Check this out:

110499 JUN 99 Engine - Intermittent Rough Idle
610198 APR 98 Vehicle - Various Electrical System Failure
650399 FEB 99 Cruise Control - Intermittently Inoperative
120899 FEB 99 Engine Controls - Idle Speed Too Low, Update ECM

 

[Kirby]

And if none of those things check out, you might want to read or watch Stephen King's "Christine".

 

[Montana]

Thanks. The dealer said there were no "warranty" or "recall" items but I forgot to check ALLdata.

Is the ECM software something the dealer can/should update? A new unit is like $400...screw that. I'll use the foot for cruise control!

 

[northyork]

I might check the O2 sensor. This can cause the same behavior however, this would have nothing to do with the cruise control. If it was the o2 sensor it would happen randomly with or with out the cruise control.

 

[Kirby]

Thanks. The dealer said there were no "warranty" or "recall" items but I forgot to check ALLdata.

Is the ECM software something the dealer can/should update? A new unit is like $400...screw that. I'll use the foot for cruise control!

Yup, it's a download from a PC into the ECU.