engine wont rev above 4000 easily in my 318i

[Olie]

i have an m10 318i that is pulling really well up until about 4000rpm then it feels like I've hit an engine limiter, it shakes and rumbles and looses power, i can rev it past it but it doesn't seem to want to, any ideas.
has had a recent service with usual maintenance issues fixed, we changed the plugs yesterday and put through a load of injector cleaner, goes a bit better and is smoother but done nothing to fix the issue.
talking to some friends into period cars they say it could be coil pack or bad grounding, i have looked all over for bad grounding and coil looks fine, any other suggestion,
as i say it definitely changes at 4000 from pulling really well to nothing.

[Grrrmachine]

Unfortunately, this is a very common symptom of a worn cam; kicks in between 4000 and 5000rpm. However, it's a lot more common on the M40 engines than the M10; which year car have you got?

Have you got any other symptoms, such as hard-to-start cranking, rough idle, things like that?

[Olie]

i would never have considered that as it is so immediate at 4200 rpm, it's an 1984 Baur TC 318i, cranking is 3to4 turns to start and idle was roughish until new plugs and injector cleaner helped it. is pulling really well, torquey and smooth until that magic number. it has done 135k but had a lot of work done not long ago, how best to check the cams, i have a digital caliper if there's a measurement to check.

[Olie]

also if the cams are wearing what should i be looking for, and what price bracket are we talking for fixing it.

[maggspower]

I don't have alot of experience with this particular engine, but have spoken to others who say the valve springs become fatigued and weaker over time. This in turn causes a phenomenon known as valve bounce, where the valve will not fully seat at higher RPM. This in turn causes lack of compression and no more go. This happens abruptly.

This seams very plausable to me, as any (convential sprung valve) engine will experience valve bounce given high enough RPM or a weak enough spring, well unless it has something like Ducati's desmodromic valve sysyem.

To check the valve train, just check visually first look for wear and pitting on the working surfaces of the cam, the springs can be checked by measuring them, but testing the force they have is more reliable. To do all this the head has to come off. The question is how far do you want to go? Just fix the problem? head rebuild........................

[DanThe]

Check the rotor arm, some have a crappy rev limit mech on them that weakens and lowers the rev limit

[Olie]

Check the rotor arm, some have a crappy rev limit mech on them that weakens and lowers the rev limit

had a look and it dosent have that, had a good look at cams aswell and they dont look too bad, maybe its not that afterall

[TDSCHRIS]

Sounds like a worn out cam to me

[TDSCHRIS]

Or your ignition timing could be out
They had to be retarded to run on lead free petrol

[johnl320]

I would be checking pulse generator in the distributor, ignition amplifier and coik for breaking down at higher revs before ripping the head off

[markus_74]

hello, Olie

sorry for hijack your thread, this topic is I want to post but you have send it first.

I have experience like you and exactly same after 4000 rpm, it won't pull fast.

I have a few afm/air flow meter to try, the one is good at low rpm feel very comfortable and no kangaroing but the weakness is after 4000 rpm it no power, but rpm is still can go higher above 4000rpm only the power is loss.

so I try other afm, this one is not good at lower rpm, so I must use a little high rpm to run the car at slow speed, but for high speed it is very good, the power is come from 1500rpm to higher above 4000 rpm or to 6000 rpm no problem, No power loss at high rpm.

so, Olie you can may be try other air flow meter I hope it can be cure your car's.

i don't know why but this is based on my experience.

regards
markus

[Billwill]

Markus, Olies motor is a M10 not a M40 like yours I think!

[markus_74]

Markus, Olies motor is a M10 not a M40 like yours I think!

thank you for your correction Billwill, but I think both engine use air flow meter? so I think it use same mechanical principle?

M10 is use bosch 0280202039? and m40 use bosch 0280202203? cmiiw

and sorry my english is not good to explain.

regards
markus

[pacerpete]

The M10 DOES NOT suffer from the worn top end issues that plague old M40s BUT there are plenty of other things that can cause similar issues First thing I would check is ignition timing,not necessarily because it will cure your problem, BUT because it will be incorrect ! It should be 30 degrees @ 3000 rpm with vacuum disconnected.

I assume your plugs are CORRECT and good and the tappets have been checked / adjusted and you have checked for air leaks.

The air flow meters on this engine were quite cranky (so much so that I recall the part number ! ) All you can really check is that the flap moves freely.

If you still have dramas you need to start looking at other things like distributors and worn timing gear (the timing light should help high light these issues )

[Olie]

wow thanks for all the help, yep definitely not the cam had a good look with a mechanic, planning to do the ignition timing soon so maybe that's it, not of the ignition hardware seems to be faulty and is all in good condition. i had a thought that it may be the ecu playing up at high revs any ideas on trying another one for a test.
also about the AFM i did try and do the common tuning trick of easing the spring off and it helped but no cure so dont think its that.

[Olie]

The M10 DOES NOT suffer from the worn top end issues that plague old M40s BUT there are plenty of other things that can cause similar issues First thing I would check is ignition timing,not necessarily because it will cure your problem, BUT because it will be incorrect ! It should be 30 degrees @ 3000 rpm with vacuum disconnected.

I assume your plugs are CORRECT and good and the tappets have been checked / adjusted and you have checked for air leaks.

The air flow meters on this engine were quite cranky (so much so that I recall the part number ! ) All you can really check is that the flap moves freely.

If you still have dramas you need to start looking at other things like distributors and worn timing gear (the timing light should help high light these issues )

just wondered if you new all the values the timing should be set at, 30 seems massive to me sure you dont mean three, and the vacuum disconnected how much would that move the timing compared with vacuum

[Das_BMW_E30]

As already stated by Pacerpete, have a look at the Air Flow Meter..

I had a C180 Merc, would not rev past 4000rpm, tried everything, Plugs, air leaks, coil packs etc.. then disconnected the AFM...bingo, thing took off and revved freely.

Bought a pattern AFM, it did the job for 11 months and two weeks, before failing, same symptoms again.

Bit the bullet, and fitted OEM Bosch Unit, problem solved!

Moral of the story, pattern AFM's are no good...

[pacerpete]

The M10 DOES NOT suffer from the worn top end issues that plague old M40s BUT there are plenty of other things that can cause similar issues First thing I would check is ignition timing,not necessarily because it will cure your problem, BUT because it will be incorrect ! It should be 30 degrees @ 3000 rpm with vacuum disconnected.

I assume your plugs are CORRECT and good and the tappets have been checked / adjusted and you have checked for air leaks.

The air flow meters on this engine were quite cranky (so much so that I recall the part number ! ) All you can really check is that the flap moves freely.

If you still have dramas you need to start looking at other things like distributors and worn timing gear (the timing light should help high light these issues )

just wondered if you new all the values the timing should be set at, 30 seems massive to me sure you dont mean three, and the vacuum disconnected how much would that move the timing compared with vacuum

30 degrees @3000 revs is correct, just in case my memory was playing tricks, I checked the BMW spec sheet of the era and yes, I am not senile, yet
Your owners handbook, if you have it, also has the timing specs.

Trying to find a modern day 'fitter' who is conversant with a timing light may be tricky though !

The unleaded setting will be less but in my experience, there is no need to retard them if they do not detonate. A 318 has too few horses to start giving them away !

On a car with electronic ignition, unless something is badly worn or it has been incorrectly adjusted in the past,the tining should not change.
I doubt if your issue is due to incorrect timing , though setting it correctly is well worth doing and will be beneficial.

[Speedtouch]

Does it have a vacuum advance diaphragm? If so, try removing the distributor cap, and suck on the end of the pipe that goes into the vacuum advance diaphragm; this should cause the distributor base-plate to move a few degrees.

If it doesn't, the diaphragm is probably perished.