E30 m3 flat spots

Hi,

E30 M3 2.3 1988 ,My car idles fine , under slow acceleration no real problems ,but under hard acceleration the car feels/sounds  like it overfuelling badly missing with lots of flat spots.I've put in a new set of sparkplugs (nil fix) and the HT leads seem to be in good condition.

Also sometimes when i turn the engine off it splutters on for a few seconds like older cars do when the timing is out ,so I'm wondering is the timing out and if so how can the timing be adjusted on an S14, ECU change?

One other annoying problem is above 4000rpm the gearstick rattles/buzzs really loudly,any ideas on how to get rid of this noise.

Cheers.

The buzzing gearknob can be sorted, but usually means replacing bushes, clips, etc, even the knob itself. If it feels sloppy, best replace the gear linkage bushes and/or the linkrods/pins. Not a bad job to do actually.

The running on... this is a weird one... I have never heard of an E30 M3 running on. But, I suppose it could if it had an air leak on the Throttle body blocks causing high combustion chamber temperatures..... leading to hot carbon deposits in the head.... leading to your running on problem, also possibly causing your "over fueling" problems.

Other than that, there are several other things which can cause your flat spots. Its best to put the car on a rolling road with an oscilloscope connected to the ignition system, a CO/HC emission tester up the exhaust and a couple of runs on the dyno while all thats connected.

Other things to check are HT leads are fully home inside the dissy cap. Check the cap for cracks, damage and all electrodes inside the cap are in good condition. Also while there, check the rotor arm for cracks, etc. Put an ohms meter across the rotor arm (middle to end of metal contact and see what the reading is. There should be a resistance, but not too high. I will need to check what it should be, but if you have a reading of infinity, althought the car will still run, it can cause the problems you describe.

AFM (Air flow meter) do wear and cause problems, Also, the blue temp sensor in the water rail above the exhaust can cause similar problems too.

What temperature does the engine run at when running normally? If just below the half way mark on the gauge, as long as the black temp sensor is in good condition, this is fine. If it stays around the 1/4 mark or lower, this is running too cold... again assuming the black temp sensor is good. The blue sensor is what gives the ECU engine temperature info. The black one does the gauge.

But a dyno run will show everything up. These engines and you E28 M5 benefit greatly to a full ignition timing and fueling remap with the AFM removed.  And if all the above doesn't help the running on, then I think the head would need to come off, decoke and modify the head ports while you're there

As to the ignition timing being out, unless there is interferrance to the 2 crank sensors or the ECU, the timing will not be out. It is ECU controlled.

Paul.

....yes he has mate and does a top job!

bbsrs wrote: One other annoying problem is above 4000rpm the gearstick rattles/buzzs really loudly,any ideas on how to get rid of this noise.Cheers.

Although I'll go along with the other comments of replacing bushes, linkages, etc on the gear-lever assembly, in MY case it was a broken valve spring, which ultimately snapped into three pieces, and ruined the cam carrier, and a few other (expensive) bits .

once I'd replaced the engine , and all the gear linkage bits - no buzz

so, it's worth a check - isn't it?

thepits,

definitly worth a look mate,

Cheers.

...funny place to have a valve spring Simon, in a gear stick!