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Discussion Starter · #1 ·
Folks,

The engine ran fine one moment and then next after a warm start it started surging intermittently at idle and whilst driving.
When if parked I hold revs steady at say 3000rpm every few seconds it will surge to about 3500rm and then die down again.
Between surges the engine is smooth as silk.
At idle the surge is more pronounced and erratic.

I have pushed and pulled the usual connections and pipes to no avail.

I am leaning towards the The fuel pressure regulator although it is fairly new with only about 2K since purchase.

Are there any other obvious pointers before I start a serious wild goose chase ....?

Any assistance will be greatly appreciated.
 

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As I understand it... this is a common occurance with the 164.. But my first item to check is the idle stabilizer on the back of the intake manifold. Then I would look at the AFM accordion hose for cracks and I would also check the resistance on the coolant temp sensor as it sends signal to the ECU to alter the mixture....

I hope this is accurate and helps..
Cheers
Martin
 

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Could be the throttle position switch: black box on the throttle housing. When mine went out of adjustment (since it is screwed on firmly this in itself was puzzling) the engine would rev to around 2500 all by itself while at idle and then would drop to idle randomly. First time it happened was at a red light and it felt for all the world like the car was itching for a stop light drag race!

This is a min max switch that clicks in the idle circuit for emissions control and also clicks in at 75% throttle for full throttle enrichment. Adjustment is easy. Loosen the mounting screws enough to twist the housing and feel for the click at the mini setting. This sould click just as the thottle is opened. The other maxi position is not relevant as it is tolerant of variation and is set relative to the mini setting that clicks in the idle circuit of the ECU.
 

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Discussion Starter · #4 ·
Folks,

Thanks for the response so far.
These look like good angles to pursue once the Christmas frenzy dies down and the turkey has settled tomorrow afternoon.

Merry Christmas to y'all.
 

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Discussion Starter · #5 ·
Martin and Michael,

Good input and I believe the problem is now resolved.

"check the resistance on the coolant temp sensor as it sends signal to the ECU to alter the mixture...."

This indeed was a problem as the plug to the thermostat housing sensor was disconnected and dangling loose and out of site beneath the upper radiator hose.

I had also noticed the engine check light coming on intermittently and the trouble code pointed at the ECU connection to the thermostat sensor.

One tends to look only at the temperature gauge sensor connections which are in plain view, instead of the nearby ECU connection which cannot easily be seen beneath the hose.

One tip which is totally unrelated: Don't close the trunk lid without pushing it down to locked.
I left the trunk lid down but resting on the lock so that I could open it easily later.
Two days later I could not start the car as the trunk light stayed on and drained the battery. GRRRRR....

Thanks again.

Neville.
 
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