Griff is oscillating around 1600-2000 RPM

[dantvrgriff]

Hi

My Griff 500 from 1997 is often oscillating around 1600-2000 RPM under low load. When cruising at almost no load it is, as if it can't decide if it wants to accelerate of de-accelerate why it jumps from one to the other. Could it be the stepper-motor that tries to regulate but is not fast enough, the fuel pressure regulator or the air flow meter (I have the suspicion that mine isn't good anymore). Any help most welcome.

Cheers

Dan

[blitzracing]

I think you are talking about the legendary "shunting" under light load. There is a whole set of reasons for it from cam type. mixture, mixture burn etc. The stepper is not no 1 in the suspect list. First make sure everything is in good shape ignition wise. and that the temp senders are giving the correct reading, and no fault codes are logged, or the ECU is not showing high levels of long term fuel trim that may reflect an AFM fault. Some cars still do it when everything is perfect, and short of fitting throttle bodies to the car you may have to live with it.

[waggy]

Couple of mid essex have had a problem with idle creeping up to 2000rpm, bit dangerous when your in top gear doing 60mph,,,
Can be caused by an air leak on plenum upsetting the idle mixture. You can prove the stepper motor by crushing the rubber pipe from the stepper to the air inlet on the plenum, the idle should drop until it stalls. If it doesnt make any difference then the plenum is leaking.

Good luck

[simonwedge]

Timing being too far advanced can also cause high and erratic idle.

[FlipFlopGriff]

Its not the exhaust touching on something metal is it?
FFG

[dantvrgriff]

Thanks for the feedback. Will begin to investigate.

FFG - why would the exhaust touching the frame be able to cause such behavior ?. Actually my exhaust does touch the frame slightly in low revs - have tried to tighten the exhaust at the silencer (squeezing the rubbers) but it still rattles when under load below 2000 Revs. When driving home last night I actually had the feeling my light was flickering slightly below 2000 revs ?

Cheers

Dan

Edited by dantvrgriff on Friday 16th September 07:22