328 Sport - engine issue
328 Sport - engine issue
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Discussion

S3_Graham

Original Poster:

12,835 posts

229 months

Wednesday 2nd February 2011
quotequote all
Afternoon,

Have a small issue with my car. Its a '96 328. It seems to be misfiring slightly but permanently. It appears to be in the lower revs as above 3k it seems fine.

The main symptom is that it feels like it holds back. If you drive along at say 60mph in 5th. It misses and feels almost like someone is dabbing the brakes.

The car starts and idles perfectly. It doesnt seem to be related to temperature as i drove it for an hour last night and although it was worse when cold it was still doing it as i got home and the car was up to temp.

Any ideas where i should attack first??

Gut feeling is that its an ignition issue so plugs/leads or coil pack.

pstruck

3,548 posts

279 months

Wednesday 2nd February 2011
quotequote all
Had very similar symptoms on a (non-BMW) car of mine. Turned out just to be the leads starting to deteriorate. Cheap first port of call on the process of elimination.

E30M3SE

8,493 posts

226 months

Wednesday 2nd February 2011
quotequote all
Probably be one of the 6 ignition coils starting to die.

S3_Graham

Original Poster:

12,835 posts

229 months

Wednesday 2nd February 2011
quotequote all
would that show up on a code reader? as in point me to the defective coil pack as opposed to me having to trial and error it?

E30M3SE

8,493 posts

226 months

Wednesday 2nd February 2011
quotequote all
S3_Graham said:
would that show up on a code reader? as in point me to the defective coil pack as opposed to me having to trial and error it?


Yes, should do.

S3_Graham

Original Poster:

12,835 posts

229 months

Saturday 5th February 2011
quotequote all
99% sure its a crank sensor. had a peek this morning (after buying a coil and 6 plugs - TYPICAL) the actual crank sensor was loose in its mounting so tightened it up and in trying to trace the wire to connector under the intake found its been massively routed wrongly and as such has been pinched against the block for what looks like years.

Ive re-routed through its plastic casing but the problem is now worse so i think i have narrowed down the culprit!

Only downside being that now the car is cutting out and i need to get it to a garage on monday preferably!! ( could always change it myself i guess )

Any idea how much they are??

E30M3SE

8,493 posts

226 months

Saturday 5th February 2011
quotequote all
A pattern part is £21.45, have heard that pattern parts can cause their own issues.

A genuine one probably closer to £90.

Last (genuine) one I bought for a VW was just over £100.

S3_Graham

Original Poster:

12,835 posts

229 months

Saturday 5th February 2011
quotequote all
oh balls. wont be servicing the car this month then. had £100 set aside for that!

Smike

24,492 posts

233 months

Sunday 6th February 2011
quotequote all
E30M3SE said:
A pattern part is £21.45, have heard that pattern parts can cause their own issues.

A genuine one probably closer to £90.

Last (genuine) one I bought for a VW was just over £100.
BMW one was £62.82 + Vat at back end of 2008........plus 38p each for the fiddly little circlips that hold the plastic cable router in place! I bought a couple smile

S3_Graham

Original Poster:

12,835 posts

229 months

Thursday 10th February 2011
quotequote all
Smike said:
BMW one was £62.82 + Vat at back end of 2008........plus 38p each for the fiddly little circlips that hold the plastic cable router in place! I bought a couple smile
errr i bought a crank sensor from GSF. £50 instead of the BMW quoted £92.

Fitted it and.....






Made no difference. Even if it is a bad part i'd expect a different fault. So car is in the garage awaiting a diagnosis from mechanic. We shall see... i left them with a coil pack and 6 plugs but they have already called and said they cant find anything just leaving the car running. No faults posted on the ECU. Very frustrating!!

john_p

7,073 posts

280 months

Thursday 10th February 2011
quotequote all
S3_Graham said:
errr i bought a crank sensor from GSF. £50 instead of the BMW quoted £92.

Fitted it and.....
I've never heard good things about the aftermarket crank sensors. OEM all the way for those.

TheEnd

15,370 posts

218 months

Thursday 10th February 2011
quotequote all
Crank sensors make the car cut out and the RPM needle kick about.
Cam sensors dull the performance all over.

Have you looked at the plugs? leaking rocker cover gaskets or water in the plug holes will also cause misfires.

Another option to check is that the ECU isn't waterlogged.
It's tucked in behind the fuse box.

S3_Graham

Original Poster:

12,835 posts

229 months

Thursday 10th February 2011
quotequote all
TheEnd said:
Crank sensors make the car cut out and the RPM needle kick about.
Cam sensors dull the performance all over.

Have you looked at the plugs? leaking rocker cover gaskets or water in the plug holes will also cause misfires.

Another option to check is that the ECU isn't waterlogged.
It's tucked in behind the fuse box.
symptoms are:

It cuts out when coasting up to junctions out of gear.

at a steady throttle position it judders about like crazy however under acceleration or deceleration and on idle its perfect.

i can sit of the drive and rev it and hold it at certain revs and its fine. it only seems to be when driving at a steady pace (motorway driving for instance) that it plays up.

TheEnd

15,370 posts

218 months

Thursday 10th February 2011
quotequote all
Are you able to get the codes read?

S3_Graham

Original Poster:

12,835 posts

229 months

Thursday 10th February 2011
quotequote all
it may be worth noting also that when i am coasting at say 60 on M'way and it starts its juddering you can watch the MPG needle move with the pause on the engine / RPM drop. (sounds like the symptoms of Crank sensor)

not changed plugs or coil yet, as i was hoping garage it went to today would diagnose which coil needed changing, as it is, they cant find anything wrong!!


ETA: no codes are reading when its idling perfectly.

TheEnd

15,370 posts

218 months

Thursday 10th February 2011
quotequote all
That could be the cam sensor, the MPG is worked out by injector opening times outputted by the ECU, and the roadspeed, so for the mpg to move at a steady speed, the injectors are changing their firing.

cam sensors, throttle position etc, something is making the ECU decide not to make power

S3_Graham

Original Poster:

12,835 posts

229 months

Thursday 10th February 2011
quotequote all
thats interesting. Cam sensor isnt too bad to change i dont think.

the MPG needle drops when the engine stutters then instantly pops back to where it should be, this all happens in say less than a second and then its fine for say 5-10 seconds and it does it again.

can only be cured by accelerating or decelerating.

TheEnd

15,370 posts

218 months

Thursday 10th February 2011
quotequote all
I'd still try and get a fault code read before, just to make sure you're going after the right one

Smike

24,492 posts

233 months

Friday 11th February 2011
quotequote all
S3_Graham said:
thats interesting. Cam sensor isnt too bad to change i dont think.
It was easier on mine than the crank sensor for sure.

S3_Graham

Original Poster:

12,835 posts

229 months

Monday 14th February 2011
quotequote all
Right, its back from the garage.

Suprise suprise they couldnt find anything wrong. There are no codes reading at all but they did confirm that they can feel the loss of power. Its due a service anyway an i'd already bought them so i got them to change the plugs while it was there to give them a job in return for their 2 days work on the car FOC!

Randomly the car is now better. Its not fixed as it still stalls and you can still feel the 'juddering' but its no where near as bad as it was. The guy at the garage has said that his next point of call would be the Air flow sensor.

What do you guys think? I'm still tempted by a cam sensor as it still feels sluggish pulling away from junctions through the revs and the idle is still perfect and i have no signs of a lumpy running.

At a bit of a loss still as i cant really afford to be chucking expensive parts like the Air flow meter at the car 'just in case'.