Hard start and rought idle/power loss

[t_marat]

Not sure if that helps, but read the problem and how it was solved
http://www.bimmerboard.com/forums/posts/360519

I will try that tomorrow, disconnecting the O2 sensor.

Is it possible to clean the MAF by spraying carb cleaner on it? I know I should not touch it, too delicate.

Can you hear how air moves inside the air intake manifold? I mean a shshsh sound with hood open. I can hear it if I rev to 2000, higher than that engine sound becomes louder. no such sound while in idle. I looked where I could, sprayed carb cleaner on hoses and under the intake manifold, but it did not see any increase in rpm. I always had this sound and thought it is normal. I think it is the sound of air moving through intake manifold. am I right?

[shogun]

I have never cleaned my MAF, it is self cleaning.

When the air-mass sensor is working normal, the hot wire does not glow. To burn off any deposits and dirt, the control system will heat the wire red hot to 1000 degrees Celsius (1800 F) for about 1 second, after you shut off your engine. This is the cleaning process and only performed if the engine is revved up to at least 2000 rpm. So starting your engine, let it idle for a certain time and shut off means no hot wire cleaning.

That is the 750 MAF, not sure if you have the same system
http://bmwe32.masscom.net/sean750/MA...leshooting.htm

Here's a link you might find interesting,all though it's a Porsche 944 AFM, he's desribing it is a MOTRONIC set up from around the same era as your E34, so they should be very similar our BM's.


http://frwilk.com/944dme/afm.htm

[t_marat]

I have never cleaned my MAF, it is self cleaning.

When the air-mass sensor is working normal, the hot wire does not glow. To burn off any deposits and dirt, the control system will heat the wire red hot to 1000 degrees Celsius (1800 F) for about 1 second, after you shut off your engine. This is the cleaning process and only performed if the engine is revved up to at least 2000 rpm. So starting your engine, let it idle for a certain time and shut off means no hot wire cleaning.

That is the 750 MAF, not sure if you have the same system
http://bmwe32.masscom.net/sean750/MA...leshooting.htm

Here's a link you might find interesting,all though it's a Porsche 944 AFM, he's desribing it is a MOTRONIC set up from around the same era as your E34, so they should be very similar our BM's.


http://frwilk.com/944dme/afm.htm

I have read in Bentley that it is supposed to clear itself. its just I remember reading about some MAF cleaner on this board. MAF on my engine is principally the same as in that link, but it has only 4 pins.

I noticed that whenever car starts running rough the exhaust gets more black and clears out as soon as engine starts running normally. smoke isn't very black, but has a tint of blackness. one cylinder not running for some reason?

Other thing. after some hard accelerations engine started making a ticking/knocking sound. sound was coming from the valve cover/intake manifold area. got scared with a thought of piston hitting the valve, but the sound was not metallic, more like something plastic hitting plastic. plus car run normal, with no loss of power. it wasn't fan, tried spinning it with engine off, no obstruction. sound was rather loud, could hear even with hood closed. after a while ticking disappeared. could this be injectors? maybe from time to time one of the injectors starting to leak badly, fouling the spark plug?

[Morgenster]

When's the last time you used injector/valve cleaner in the tank?

[t_marat]

Last year. But after using the cleaner, I did not see any difference in how the engine ran.

[Morgenster]

Last year. But after using the cleaner, I did not see any difference in how the engine ran.

Maybe now you will?
I'm not too sure about your problem, but with the added info on the piston I'd say take a look at the injectors. I never get black smoke, ever. So one cilinder at least is not firing on startup and maybe cuts out once in a while.
However, that won't explain why your engine runs fine right after a reset and starts coughing after a while. How long did the effect of the reset last?

[t_marat]

Maybe for a day I think.
Coughing is also strange. Sometimes there is no coughing, sometimes it starts coughing badly (but again only when I am braking with engine).
Somebody here told me it could be a crankshaft sensor. Can it go bad from time to time, especially when its hot? If it isn't functioning properly then I think fuel pump won't pump as it should and ignitiion will also be wrong (pinging). It kind of fits perfectly.
But it doesn't explain the knocking noise.

[Morgenster]

Maybe for a day I think.
Coughing is also strange. Sometimes there is no coughing, sometimes it starts coughing badly (but again only when I am braking with engine).

Are things getting worse?
Engine braking should cut off fuel and spark so the engine shouldn't cough when you do that!

[shrike071]

It could also be the DME itself going out. Electronics do all sorts of odd things when they begin to fail...

[t_marat]

how strange it is, but it coughs only while braking with engine. meaning releasing the gas pedal while in motion in say 3rd gear. by coughing I mean the puffing sound that comes out of exhaust (?).