I have an INTERMITTENT sputtering/stalling/bogging issue that shows up when the car is at full operating temp--oil and coolant. When the problem crops up, it requires nursing the car along in 1st gear. Sometimes restarting it makes it run normal again, other times not. It doesn't happen all the time--there are days when I drove all over with the car and no problem. Other days, once it reaches full operating temp, it surfaces.

I replaced the fuel filter, and the problem didn't surface for a while, but then it happened again.

Other potential causes, based on what I have read here and on S14.net, are:

- engine ground (I replaced this yesterday--didn't test yet at full operating temp, but I noticed the gas gauge works again!)
- Idle Control Valve
- Oxygen Sensor
- Throttle Postion Sensor
- Coolant Sensor(s) (are there 2?)
- Air Flow Meter
- ECU

I'd really like to find the problem and fix it, as I'm having trouble selling the car.

Thanks for any tips you can provide.

Paul

i saw your FS ad on s14 and i cant tell you how much i want to buy it, but being a college student have no moneys and i dont want to have to be paying a loan off in school. it kills me


also id start with the o2 sensor and maybe crack open you AFM and look and see that it doesnt have any heavily worn spots along the tracks

It's free and easy to check the condition of the distributor cap if you haven't. I've had a bad cap exhibit similar symptoms.

Coolant Sensor(s) (are there 2?)

yes there are 2, and not an expensive fix. you can get them at BMA parts.

It's free and easy to check the condition of the distributor cap if you haven't. I've had a bad cap exhibit similar symptoms.

Cap has only 100 miles on it, and I just checked--it's as good as new inside. Plugs look fine too.

How about the fuel pump?? I know on 84-87 models there are 2 fuel pumps,a transfer pump(supplies fuel to main pump) in the tank and the main pump under the drivers rear door. 88' (like yours, unless it's a late 87) and up, have just the one pump in the tank. Bentley manual says the transfer pump (84-87) can go out but still run the car, just starves the main pump,and happens in hot weather. If you see a pump under your car you have a late 87',....unless M3's came with 2 pumps. :confused Just thought i'd throw out a rambling idea . :D

Thanks! I do have 2 pumps. The one under the driver's door was a lot louder before I replaced the fuel filter.

I have the same issues, it looks like the AFM or coolant temp sensor are items to check right away like your list shows....

Hi people,
Hoping this thread might help some of you who have been struggling with this annoying problem.

I have completed reworking the following systems over the past year;

PCV, Fuel pressure regulator O rings,injector O rings and all viton seals on intake manifold as well as the majority of the vacum lines.

fuel pump (old one was really noisy and pressure was a bit low), feed lines and filter

Camshaft cover gaskets (don't forget the isolator rubbers too- 14 of them on non-vanos engines), Plug boots, and three coils (abeit used ones), oil filter housing to block gasket and O rings (that's another story on that one if anyone is curious)

Yes, after 15 years all the gaskets do get hard and will leak. What appears to happen with the plug boots is that they not only deteriorate with exposure to the hot oil but they also absorb any moisture that might collect on the engine once it cools. Rainy days in high humidity were the worst for misfire,backfire, stumble.

After replacing the plug boots, things were very much better, I was still running single mass (electrode) NGK plugs so I screw'd-up my courage and got the dealer quoted 4mass plugs. Suprisingly they do not quote bosch plugs for this application, they quote NGK's BKR6EQUP plugs. In Canada, where everything costs too much, they are $23ea at the dealer, I got them for $13ea at a local parts store.

I also noted that I had evidence of arcing and (slighly) changed primary resistance on 3 coils (sure enough, #5,4, and 3) all of the coil cases had minor cracking. But they are OEM used coils out of another '92. These coils seem to get more heat soak than the outer ones that is probably what fails them.

Once changed, the car runs much stronger at the bottom end with the air-cond off. The sound of the engine as it winds up is wonderful. BUT- with the air on (and therefore the idle speed and mixutre are bumped up) the same low end (under 2000 RPM) stumble is there.

Now the wife is looking at me with that really annoyed, Why TF did we spend that extra money for, look.

I tried cleaning the MAF unit. It was very clean to begin with, no difference. Mechanically the motor is in good condition. Compression is strong and even. Injectors otherwise seem to be clean, plug colour is normal and consistent on all plugs. ICV has been meticulously cleaned and restistance checks to the manual specs too. DME flooding has also been checked and ruled out, airbox plenum drains are clean and dry.

I know this has to be a fuel mapping or an ICV control related problem. When the air is not on the motor runs very good and stong like it should.

Still the coils? I'm not so sure. I don't want to fork out the $$ for coils that I may not need to change yet.

Any other suggestions ?

Grimsby325is

PS- Oh ya, the voltage part you may be wondering about? The 4mass plugs behave like surface gap plugs (anyone remember those old days from Mercury marine?) therefore the voltage requirement of these plugs are definetly higher. However, if the coils are in fact breaking down, what I don't understand is why the problem does not get worse under WOT-FULL RPM- FULL LOAD conditions like you would normally expect from a voltage requirement problem ???

I had been having a stumbling problem with my M3. A member on S14.net saw that I JB welded the elbow on the plenum because they are press fitted and it is known they come loose. He also mentioned that there is another one that goes into the TB. You will see the hose it attaches to the Brake Booster. I was able to take it and remove it by hand. Mine moved freely no problem. Well I JB welded it in place. Guess what no stumble anymore. If you can move the metal piece by hand that could be your be your problem. I did not see it in the things you fixed.

Also if you want to check for vacume leaks take your fan off and get a propane torch. Open up the gas and move it around the car. If you get to a place and your idle changes that also can be a sign of a vacume leak.