Engine hunting on idle.. M42/318is

Mon Jun 11, 2018 12:06 am

Hi everyone,

need some advice please,

my engine is hunting on idle whenever it gets up to temperature.

So a bit of history to let you know whats already been checked etc:

Engine was originally not idling until it was warm, then when warm, idling fine, I wanted to get to the bottom of it not idling when cold and found out the pipe going from the ICV to the top of the engine was split, as was the pipe going from the ICV to the air box boot. Last weekend i replaced these for new hoses. Whilst doing this I realised (shock horror) I had forgotten to connect my fuel filter since putting the engine in say 2 months ago... so it has been driven for two months with no fuel filter connected. Awful I know. So anyway, had a new one and got that connected up, cleaned the ICV, throttle body and replaced the air filter whilst I was there.

I'm now worried that it could be injector related.. due to the lack of fuel filter? but then it does seem strange that all was fine until the ICV was connected up properly with hoses that weren't sporting huge splits..

any advice much appreciated!
thanks!

Mon Jun 11, 2018 9:26 am

Perhaps try disconnecting the battery, leave it for a while (at least 20 minutes or so) to reset the ECU, reconnect then let it idle for at least 10 minutes to learn the base idle settings. Switch off, then go for a drive throughout the rev range.

Also check for air leaks around the throttle body and inlet manifold gasket - with the engine idling, spray WD40 around the gasket and if the engine speed briefly increases, you have a leak.

Mon Jun 11, 2018 2:07 pm

you may have another vacuum leak somewhere. and by fixing said issue the leak is more prominent now, as more air is being stucked in there. there are 3 ways to test for a vacuum leaks . smoke , propane gas or carb claener. always HAVE A FIRE EXTINGUISHER TO HAND . you tube it plenty of example on there.iirc Eric the car guy got a good one.

as for the injectors they have replaceable filters in the very top of them, which can be swapped out . again youtube it reconditioning injectors petrol. but its probably not that unless you run the tank very low on fuel , there is a filter in the tank anyway.

could be an issue with the blue coolant sensor. the throttle position sensor or not so likely the a.f.m. air flow meter
info on here wiki.

Mon Jun 11, 2018 2:12 pm

air filter won,t make any difference, but usual service items plugs dizzy cap rotor and leads could.
and there is a connector under the inlet manifold for the injectors that corrodes. do a search on here. mainly 6 pot i believe.

Mon Jun 11, 2018 7:53 pm

thankyou both so much for your suggestions.. i'll give them a go and report back

Sun Jun 17, 2018 8:57 pm

You can save yourself a load of hassle by binning the throttle body heater and the pipes that feed it. Next check all the hoses for splits and make sure both the throtle butterflies are fully shut when the car is at idle. Do not adjust the screw on the AFM, if the plastic plug that covers it has been removed then the chances are someone else has done so and you have another problem to deal with.

http://www.e30zone.net/e30zonewiki/inde ... ody_Heater