1986 Reliant K-Car up and down revs

Hi. My 86 K-Car has started to rev quite fast upon start-up and then it
kicks down only to go back up again over and over. When it finally
drops enough I put it in Drive, but it seems to accelerate on its own
without even touching the gas pedal. When I get to where I'm going (and
the engine's warm), putting it in Neutral or Park only causes the revs
to speed up again. I don't want to shut it off when it's revving that
fast.
Thanks for your help (I have to make the K last another year).

 

I would gather that you have tried to dump diagnostic codes and didn't get
any?

I had an O2 sensor go bad on my 88 Reliant. Gave the same symptoms.

 

It's probably the AIS (automatic idle speed) motor. It could also be a
cooked wiring harness, which is what happened with our old '88 Omni.
It would too fast -- sometimes as fast as 2,400 rpm. The key was that
it was more likely to do it it wet weather. The fix was to open up the
wiring harness and re-insulate the wires within. The mechanic who did
this said that he'd seen this a few times before, especially with
Omni. His theory was that the tight engine compartment on 2.2L Omnis
did not allow enough cool air to travel over the engine, and the
insulation in the wiring would be damaged by heat. We'd gone through
two AIS motors before we got it fixed for real. It never did generate
any codes.

I'm assuming that you have either the 2.2L or the 2.5L.

 

Hi, Carl. Thanks for your reply. The diagnostic codes didn't indicate
any problems. I'll look into your suggestion.

 

Hi Jeff. Thanks for your kind input. It is a 2.2L engine. I'll have
your ideas checked out.

 

Can you be more specific on which wiring harness needs to be checked in
this situation, I have a 2.2 turbo '85 that has also been doing this,
random (but starts to want to do it after warms up) revving and
lowering of idle. Can rev way too high. All vac hoses
repaired/checked (which fixed a problem with the wastegate not kicking
in), removed and cleaned the whole throttle body etc. No codes when it
does this. Definitely the idle motor is activating the overrevving cuz
if I disconnect it the overrevving goes away (but I can't run the car
like that of course or it won't rev high enough for cold running.) Is
it only the wires for the idle motor itself that are in question here
on the insulation, or ANY wires running around under there?
thanks!....Frenchy

 

Frenchy, the harness he is referring to is not the same on your vehicle. On
Haywards vehicle the harness would rest on the intake/exhaust manifold and
short out causing the AIS motor to go crazy, all he has to do is check for
damage to the harness and get it off the manifold, You could have a problem
with the TPS sensor, coolant temp sensor, map sensor or AIS motor.
If it were mine I would have the system scanned to see the values of the
sensors. A sensor can be out of calibration without setting a fault code

Glenn Beasley
Chrysler Tech

 

Thanks very much Frenchy and Glenn for your help. It was the TPS
sensor and after replacement it seems to run okay now.

Michael.