325i jerks at about 2K RPM

[sean_318i]

This is driving me mad. Engine idles a little lumpy accelerates fine but jerks like a bitch
when holding constant speed or light throttle feels like someone is kicking the back of my seat
its also running very rich drinking petrol and sometimes puffs black smoke on acceleration.
Its a 325i tourer 1991. Fitted brand new AFM, Press Regulator, Blue temp sensor, tried different ECU,
Checked main engine plug and all other plugs adusted TPS and did all other checks that i could find in haynes and zone.
Please HELP.

[NH325CAB]

Have you checked the distributor and rotor? Mine did the jerky thing for a while until i replaced them and then it was fine! Also checked the valve clearances too.

[sean_318i]

Yep cleaned up cap and leads set tappets and did a compression test.
Tomorrow im going to change the injectors They have done 165 k miles ill check the inlet manifold gaskets too but this doesnt explain my over fueling problem.

[E30BeemerLad]

my money is on manifold gasket, spray some WD40 or carb cleaner around it where it bolts to the head, should restore normal idle very briefly

you have exactly the same symptoms mine had and this was the culprit

[sean_318i]

Was Yours over fuelling too cos mine is really bad its hard to stand behind it when its running.

[sean_318i]

I changed injectors and fuel rail no change and sprayed wd40 around intake pipes inlet manifold and throttle body still no change. Running out of ideas now.

[Martinaston]

It could be play in the diff
Crawl underneath and with the car in 1st or 2nd and the handbrake on, see how much the prop shaft rotates. On a new car it won't move at all.
It's a problem that only becomes apparent once the engine is working normaly and not idling too fast.

It can also be wear in the drive shaft's and the gearbox. Ԛ£Ã”šÃ‚£Ãƒ”šÃ‚£Ãƒ”šÃ‚£Ãƒ”šÃ‚£Ãƒ”šÃ‚£

[sean_318i]

I tried wobbling the prop im only getting about 2 to 3mm play which i dont think is enough to be concerned about. I think its more of an engine running problem anyway. i just swapped the dme relays from my 318i to the 325i and it made no change either.

[Martinaston]

Did you try another coil ?
Have you changed the air filter ?

[sean_318i]

The air filter is brand new i didnt try the coil yet because it runs fine when accelerating hard i thought these ignition faults would only show up when the engine is under load.

[Martinaston]

If accelerating hard is not under load then what is ?

[sean_318i]

What i meant was i didnt check the coil because the engine runs fine when under load / accelerating. Anyway i just changed the coil a minute ago and it made no difference except that it started a little easier i thought.
Also both coils have "TCI COIL" marked on them and i thought that the tci system preceded the later motronic system could these be the wrong coils altogether. The 318i took the second coil from ran sweet till i parked it and is the later type motronic injection.

[Martinaston]

Well i'm as stumped as you

Mine has a problem similar to your's in that it jerks when running at a constant low speed and can only be cured by dipping the cluth and accelerating again.
This is down to a knackerd diff and nothing to do with the running of the engine.

You can sometimes spot this if the car appears to run ok from cold but then it starts to happen once the engine has warmed up and idling at the correct speed.

Try coasting along in second without touching the pedals with the engine cold and then do it again once the engine is at running temp and see if you can feel a difference.

If you have a rough idle it could be down to clogged injectors that are not atomising the fuel correctly at low engine speeds and is not related to the running problem you described. It will also cost you on the fuel economy and rot the exhaust eventualy.

[Martinaston]

As for the coil i think it's different between the M40 and M20 engines.

[tonyppe]

sounds like an air leak on the induction side.

like someone said before, spray wd or carb cleaner around all the joins with the engine running. the engine will change speed if the air leak sucks in whatever your spraying.

if it were to do with the diff, it would happen whatever rpm if your holding it constant. plus it wouldnt judder like you have described.

[sean_318i]

Thanks lads for all the help. Im just back from dropping it off at a local garage heres hoping it doesnt cost too much to sort will get co level sorted while its there. Ill post up my results. Thanks again.

[MONSPORT42]

I had a rough running problem which turned out to be a dodgey connection in the connection block situated on the block under the inlet manifold which governs the inectors. The rubber boot had come off and it had dirt in it. I also notice that no one has mentioned cleaning and checking the ICV which could have an effect at only 2000rpm.

[sean_318i]

Ive already checked these plugs on both sides and are perfectly clean unfortunaley also checked resistance of ICV and cleaned several times seems perfect. Thanks though.

[Ratfink]

It was the HT leads making mine do it

[fannyj]

Hi
I have a 325i, got it in almost perfect condition has 149 000km's on the clock. It does the exact same thing as yours. Had it serviced at the agents recently and i descibed the problem to the BMW technician when i dropped her off. They couldn't diagnose the problem. I checked the service history of the car and noticed that the car has had this problem for the past 8 years!
Got new injectors/coil/plug wires/AFM/ICV amongst a whole host of other things.. I aint planning on spending a penny more to solve it. I just accelerate quickly beyond 2000rpm.