Misfiring.....

Hi All,

My 89' 318i is missing at low revs, I've tried a lot of things including, new plugs, new leads, new coil, new battery, checked distributor, replaced vacuum hoses, (although not sure if I did them all but the two I can see are done)

I'm now lost as it is still missing but as you go higher up the range the misfire stops.

Does anyone have any suggestions? Help/advice would be greatly appreciated!

Thanks in advance....

Originally Posted by Luke1985

Hi All,

My 89' 318i is missing at low revs, I've tried a lot of things including, new plugs, new leads, new coil, new battery, checked distributor, replaced vacuum hoses, (although not sure if I did them all but the two I can see are done)

I'm now lost as it is still missing but as you go higher up the range the misfire stops.

Does anyone have any suggestions? Help/advice would be greatly appreciated!

Thanks in advance....

I presume this is the 318i M40?

Only use the NGK spark plugs...strangely the E30 does not like Bosch plugs.
If you replaced the leads...did you get OEM ones with the extra lead wrapped around lead number 4 to set the timing? It will run without that extra lead but not as good.

You need to spray some Carb Cleaner around all the hoses and gaskets in the inlet area to look for air leaks...very common on an M40.

Could be the AFM, the camshaft timing or camshaft wear.

You need to have a look at the cam belt to check its condition and check the cam timing while you are about it.

The best site for advise on the M40 318i is the UK site:http://www.e30zone.net

Thanks for that,

I used Bosch super 4's and non oem leads, updated 8mm... The car was running poorly before I replaced plugs and leads and the cid you described broke....oem leads are seriously expensive but did not realise replacements would be a problem otherwise would have paid the amount.

Am going to get the timing looked at to see if that's the issue and will check for leaks....

The miss does disappear when you rev the engine up...

Sent from my HTC One X using Bimmer App

And yes its the m40 motor.

Sent from my HTC One X using Bimmer App

Originally Posted by Luke1985

And yes its the m40 motor.

Sent from my HTC One X using Bimmer App

The e30zone site has a good Wikki on the M40 and also on replacing/timing the cambelt

It could be the miss-fire is masked at higher speed rather than going away. Also get injector clean (on a rig, not in a can). Check FPR hoses and unit for vacuum leaks.

Looking at it today...took lead 4 off and no change in engine idle, thinking it may be an injector and as you said bmwfatherfigure higher revs may have been masking it. Will try replacing this injector. Have a good spark and when I removed plug it was damp...maybe not enough fuel getting through...

Sent from my HTC One X using Bimmer App

If the plug was wet it's getting too much fuel or that plug isn't firing.

+1 Ken. If one injector is bad get them all cleaned and flow tested.

Thanks all for continued support...got 4 recon injectors on the way...

Also I'm going to replace fpr for piece of mind as I've got one available to me for free.



Sent from my HTC One X using Bimmer App

Recon is good if from a reliable source. Hope it fixes things up..

Originally Posted by hornhospital

If the plug was wet it's getting too much fuel or that plug isn't firing.

Or that the injector is spraying a stream of non atomized fuel...which won't burn.

m

True.

Is there a spark going to #4?

Thanks all,

I have resolved the issue, decided there must be something wrong with injectors, took everything off, got to number 4 and as I withdrew it it was carbon city and the jet fell off! Coupled with a blown out lower manifold gasket and seriously unhealthy looking icv I realised where the issues were.

Fitted four recon injectors, cleaned icv (extensively), replaced gasket put it all back together and TA DA! Perfect.

Thank you so much for your suggestions and theories all this info helped me a lot!

Luke