Idling up and down between 500-1500rpm

[philKS2]

Argghh.....


My car has been running so sweetly the last couple of months... just beautiful.. and since I started using 98 RON, she's been even better. than on the 95 RON.


BUT on Friday last week, I let her run very low, and put in half a tank of 97 RON.. and within minutes of leaving the garage., she's changed... symptom is that at idle she's reving at anything from 500rpm to 1500 rpm, up and down... and so I even stalled in second at 20mph (gentle pull away)

Could this just be the petrol..its rather like my old Cavalier when it had a loose air hose into the petrol injection.


Phil

[A80Avant]

dont despair.It has happened to me a few times.Just find a way to erase the fault codes,do a few runs and it may come back to normal.All that of course supposing you have a fairly new lambda and maf

[frazz]

hiya mate,
you could use whats in the tank and fill it back up with 98 ron and add some fuel treatment at the same time then see how it runs. Failing that have you checked your idle air control valve.

[UrS4boy]

Well, you might have taken on a load of bad fuel but if I didn't think that, I would be pointing you to the N71 Idle Stabilization Valve.

Follow this link to N71 info

[Rusty]

Clean the ISV out give the MAF a quick squirt of carb cleaner whilst you're at it, should go a long way towards sorting it out, I think the fuel issue is a bit of a side issue, you need to run 98 to get anywhere near full performance, Tesco 99 is the best stuff I've found

[ifa]

Test idle switch and TPS.

[popdemonic]

It happended to me a few times.Simply the best,just try to remove the N71-Idle Stabilisation Valve and clean it up the carb cleaner.Anyway,Don't forget your Throttle body as well.hope will helps.

PS.when you disconnected the wires. it's good idea to clear the sporadic fault after finished everything.

[S4 CRUISER]

Hi. Check your intake pipe on the inlet manifold. The short black rubber hose. Common for splits.

[LVrainman]

got a bit of same problem.. jumping idling revs while disengeging clutch. and then after 3 jumps ir stabilizes. but sometimes it starts to jump again by itself while waiting to the green light. measured the resistance of ISV it was 9.x (something)... should be OK. disconnected the connector of ISV, and then the revs went stable on ~1000 rpm on warm engine, but should be ~800.

please any comments on my issue...