running a bit rough

[kingstonbe]

i've been bugged with a problem with my '89 325i sport for a few months now... It's running a bit rough at idle and sounds to be missing slightly and still if i hold it at higher revs it persists. The car failed its test on emmissions, HC's were more than double the maximum allowed, but the CO's were well below the limit. when driving, there is a harsh chug below 1500 rpm when off the accelerator

I've tryed a number of things to cure it;
-replaced the spark plugs with NGKs (old ones looked fine/ very slightly oily)
-spark colour is blueish orange, more blue than orange.
-ht leads look to be in good nick from a brief visual inspection
- the air flow meter flap is moving smootly and appears to close properly,
however using an ommeter on the unit revealed an irregular build up of om's as the flap is opened gradually to the open position
-fixed a loose air hose connecting the idle air stabiliser valve to the intake mainfold (bypasses throttle i think) this improved the up and down idle.
-K&N filter is in good nick
-Compression test revealed compressions between 10.5-12.5 bar (which i understand is ok?)
-patched a small hole in the centre section of the exhaust (scorpion s/s back section)- no noticable improvment
- i've put injector cleaner in the petrol, but didn't have any noticeable effect
-there is supposed to be an uprated chip installed by a previous owner, i haven't gone near the ecu, but i have the original chip.


I think this one could have me beat, and i'm contemplating handing it over to a specialist to have it sorted, but before i do, i want to pick the minds of all you fellow e30 enthusiasts and try to solve this one wothout the expense of a specialist. well guys, any suggestions??

[Martinaston]

Did you check the cap and rotor arm for wear ?
Hopfully someone else will help with the airflow meter readings but it doesn't sound right to me

[kevin316i]

I'm having a similar problem with my 318is. Got the car serviced including plug and plug lead change, but no improvement in problem. Hoping to get it seen by a specialist soon. I'll post whatever info I get, might be of help.

[kingstonbe]

didn't check the distributer itself, but i think its more llikely to be a feuling problem. ya i don't like the airflow meter readings- has anyone else know if these readings are normal?

will also post any info if useful, cheers.

[kingstonbe]

also changed the oil and discovered that there is no oxygen sensor as it was de-catted from new. By adjusting the hc mixture at the adjuster on the air flow meter i believe it could bring the emmissions down to pass the test, but will the car run right?or make proper power? and can this cause long term engine damage if it isn't set right?

[kevin316i]

I think you can only adjust the CO, not HC. The high HC levels are due to unburnt petrol going through the exhaust, so the underlying problem needs to be fixed to reduce these.

[kingstonbe]

apparantly the blue temp sensor is known to cause these problems aswell. does anybody know how to test these? or why it would cause this problem?

[Martinaston]

The temp sender fails and the ecu assumes the engine is cold so it adds more fuel.
You can adjust the screw on the airflow meter to get it through MOT then put it back to run a bit rich after. (just dont get stopped and checked by the old bill)