wedge 350i idling

[SteveBikeandAuto]

Hi All

I know this subject has probably been done to death, but forgive me, just joined and thought better to start new. Got a 1986 350i, doesn't want to idle below 1100 rpm and shunts at low revs. Have fitted new plugs, new leads,checked for air leaks and checked timing, none have made any difference. What may be a clue is that when idling, if I lift clutch just enough to engage,then put clutch in again, the revs drop to 600rpm. Can any of you knowledgeable folks point me the right way?

[Wedg1e]

Ignition timing, fuel pressure, AFM monkeyed with, stupid cam... etc etc etc etc etc.....

[mrzigazaga]

Hi mate...Sounds a bit strange...Does it do it all the time whether its hot or cold?...Check to make sure the throttle butterfly is not sticking..Or it might be the idle speed control thingy on the side of the plenum getting stuck...If you take it off to clean it make sure you use a new gasket, Even some gasket paper and some blue hylomar or similar to make sure it is sealed properly..Ziga

[mark387mw]

I've had my '85 350i 25 years now and it's always been 1100 - 1200 at idle. A bit high for my liking but it's where it works.
I got it from HHC and has had FSH for at least the first 10 years and that's how they set it. Not changed since!

Does adjusting the idle slightly higher, or adding a few more revs, get rid of the shunting?

[mrzigazaga]

mark387mw said:

I've had my '85 350i 25 years now and it's always been 1100 - 1200 at idle. A bit high for my liking but it's where it works.

Hi mate...That does sound a bit high..Mine idles at around 950-980rpm and some say that is even too high but thats where its happiest, As i understand it the bigger V8's tend to be around 700-800rpm...But like they say.."If its not broke then don't fix it"...Just wondering if the OP's idle is higher when cold as it should be or if something like the temperature sender or EAV is not working as it should...I would check the condition of the plugs after running it a few times to see if its running either rich or lean..As i have learnt it is far better to systematically check one thing at a time..The scatter gun approach might yield results but doesn't determine the actual fault and teaches you nothing, Far too often the AFM or ECU is pointed at as the problem but turns out to be something else...
I had symptoms that were similar to those of a faulty ECU...AFM...TPS...Temperature sender...etc etc..But turned out to be a failing fuel pump and a dodgy king lead.

I learnt with the 280i that changing one thing at a time taught me more about pin pointing the issue than just running blind...It helped me to help others....Cheers...Ziga

[jon haines]

Well i have had this in the past and it can be a question of going through a process as Zig suggests. First thing i found was that they dont like the cold start injector so disconnect it. Assuming its set up right it could be afm or ignition amplifier both of which i have had to replace under similar situation as described. My 350 idles at 1100 - 1200 cold dropping to 750-800 when warm then to 500-600 when hot but dosent conk out.

[adam quantrill]

with these tricky ones I would start with the unexpected - so clean all the earth straps at both ends and make sure the strap underneath between gearbox (or engine) and chassis is there and connected.

[SteveBikeandAuto]

Hi Guys

Thanks for all the responses and advice, certainly plenty to think about there. Just to answer one or two of the qestions, the car idles at a steady 1100 from cold. Once it has warmed up, the idling is as described consistently.From what a couple of you are saying, idle speed of 1100 isn't uncommon. I just worry a bit about idle at that level for any length of time as the temperature needle soon rises. As I said, I can drop it by just engaging and then just dipping the clutch again-I just can't help thinkong I shouldn't have to do that.I will check the basic things mentioned and update-Thanks again for all the responses.

Steve

[keatsie]

Switch the ignition on, with the engine off check the voltage on the yellow wire of the throttle pot. Make sure it read between .33 and .35 volts.

Run the engine and measure again. If it is out, check and adjust the bad idle setting.

[SteveBikeandAuto]

Hi All

Just a quick update. I checked all hoses & connections, removed plenum cover, cleaned out and replaced, checked timing, new plugs and leads have been fitted, checked earth leads and electrical connections. After all that, there was an improvement, but still not right. Finaly, I adjusted the idle on the AFM and that seems to mostly have done the trick. Idle is not perfect, but doesn't fluctuate anything like as much and is much smother to drive at low revs. I plan on changing the camshaft over winter, but in the meantime, happy days- thanks for all the advice.

Steve

[celcius]

Nice one