idle problem.(A new one!)

Fri Mar 13, 2009 10:24 pm

i have a 318i auto e30 on a j plate , M40 engine i think. it starts no probs but when its from cold it idles fine until i put it into drive or reverse. as soon as i do this the revs fluctuate badly and sometimes stalls. it drives fine once its rolling. when its warmed up it still drives fine untill i slow down. when braking it seems to take a while for the power to subside, almost like im braking and holding the throttle open at the same time? then the power drops off we brake ok. when at a standstill with my foot on the brake if its in drive the revs fluctuate once again which makes the car surge forward, almost like blipping the throttle with the hand brake on, the rear of the car dips and rises. as soon as i let the brake off it moves off smoothly and drives fine. at park with the engine running appling or pumping the brake pedal makes no difference to the revs. please help!! cheers.

Sat Mar 14, 2009 10:24 am

Sound's like an air leak fella. Check the intake side for leaks including the manifold gasket.

Sat Mar 14, 2009 4:35 pm

I had that on mine too - after i changed the airbox I tightened up the hose from the AFM and it seemed to sort it (happy accident) - as Zaust says, it sounds like an air leak.

Mon Mar 30, 2009 9:29 pm

right, here we go! found the afm pipe was split, so replaced it. it runs better but the revs sit at about 1300rpm at idle!! it hesitates slightly when you blip the throttle.
any more ideas?
cheers.

Mon Mar 30, 2009 11:41 pm

Sounds like you still have a leak somewhere. I'm sure I read somwhere on here that engines idle faster when cold too, but not by that much.

Sun Apr 12, 2009 8:10 pm

new update. i changed the afm to see if it was faulty, but the problem remains. in order to locate the air leak i have ended up stripping down the whole inlet manifold to replace all the gaskets to make sure.
my question is about the injectors. am i right in thinking they have 'o' rings on them? do they fail often? is it worth replacing them? how hard is it?
cheers.

Mon Apr 13, 2009 11:50 pm

anyone? please?

Tue Apr 14, 2009 7:37 pm

the injectors do have 'o' rings on top (fuel) and bottom (to seal the the manifold). i'd be suprised if they've failed enough to get a big air leak though, they're pretty tight in there.

have you tested the ICV or tried a new ICV?

TPS set correctly?

do you have aircon? turning this on will increase the revs to accomodate the additional load from the compressor

Sun Aug 23, 2009 1:29 pm

back again!!! have changed all the inlet gaskets and rubber pipes, brake servo, icv (twice) afm, rocker gasket and injector o rings. it now runs ok ish but when it get up to running temp the revs go up nearer 1300 and fluctuate.any ideas guys?
cheers.

Tue Aug 25, 2009 9:10 pm

the idle speed is controlled by the ECU. If the ICV is working correctly (inc getting the correct signals from the ECU - check wiring and connectors) and there are no air leaks, it whould be spot on.

the only other things that i can think of that will increase idle speed are the aircon connection (higher idle with it switched on to help wit the compressor load) and on some auto cars (not sure on E30's, not had an auto) the idle picks up when the gearbox is put into drive.

sometimes a slow idle can be botched by a dodgy previous owner (there must have been at least one by now!) by using the aircon function, maybe it's worth investigating this. probably tapped into the loom from the aircon plug under the dash. might be worth pulling the dash trims off (drivers side underdash trim iirc) and checking out any obviously non standard wiring to see what's what.

Tue Aug 25, 2009 9:10 pm

any ideas guys?

Tue Aug 25, 2009 9:12 pm

thanks gareth.

Wed Aug 26, 2009 12:23 am

thanks willnz, any info will be great. but what is thou in metric? hehe
cheers. bill.

Wed Aug 26, 2009 8:04 pm

hehe. i was born in oz but english parents. the bushwakka come from my offroading passion( more like my driving style!!)
nowt wrong with imperial just ive got metric filler guages! hehe

Thu Aug 27, 2009 7:07 pm

Hello Bushwakka.
I've just been reading this thread and have the exact problem as you explained in your first message. I've just brought a new throttle inlet rubber cos mines splitt but i've yet to fit,hopefully it will solve it?
Did you rectify yours and without being too technical,cos i'm not,what exactly did you do??