Pinging M20b25?

[Kepes 231]

Hello,

I think my E30 may be pinging, however I have nothing to compare the noises/symptoms to so not sure. M20 doesn't seem like an engine that would ping but who knows.

Basically i'm hearing a 'rattling' noise from the engine. However only under certain circumstances. 1) When low RPMs in 2nd or 3rd and I floor it, I can hear the rattle. As the RPMs get up a bit (2.5-3k) the sounds goes away. 2) When under load (driving up a hill) and flooring it the rattle sound will audible at about 4k RPMs until ~6k or whenever I change gears. Don't hear it on deceleration etc.

It is a metallic sound, and sounds a loose piece of metal or something being thrown around the engine (which it won't be). I don't really know how else to explain it unfortunately! Head has been resurfaced when I did the head gasket, and engine has 325kms on it so perhaps compression has increased and I need to use a higher grade fuel (currently running 91).
Read online that it could be the crank bearings. Only other thing I can think of is pinging/fuel knock or whatever it's called.

If anybody has experienced something similar and may be able to shed some light it would be greatly appreciated! :~)

[hotwire 352]

Has yours got the conventional distributor? If so - check the ign timing. Depending how much was taken off the head may be the cause.

Also, don't run it on 91, 95 at least, 98 best.

[scottbeattie 63]

My E28 pinged on 91, it's an M20B27 though and has quite high compression. Changed to 95 and hasn't pinged since. As above, if the head has been skimmed, compression will be a tad higher possibly causing the pinging. Good thing fuel is cheap at the moment!

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[Kepes 231]

Has yours got the conventional distributor? If so - check the ign timing. Depending how much was taken off the head may be the cause.

Also, don't run it on 91, 95 at least, 98 best.

Does have the conventional distributor - however I think the timing is ok as even before doing the head gasket it would rattle, but not quite as often as it does now. I'm thinking it will be compression. Will run 98 from Mobil for my next fill and see if it helps.

My E28 pinged on 91, it's an M20B27 though and has quite high compression. Changed to 95 and hasn't pinged since. As above, if the head has been skimmed, compression will be a tad higher possibly causing the pinging. Good thing fuel is cheap at the moment!

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Does the b27 have the same compression as the b25? Also when it was pinging did it sound like a rattle from the engine? I've never heard a car ping so i'm not really sure what it is. Very lucky fuel is cheap at the moment!!

Are there any adverse effects of running 98 over 95? It wouldn't be too high would it. Only reason I ask is because I much prefer fueling at Mobil than at Z.

[polley 916]

Hello,

I think my E30 may be pinging,

If its doing it all the time, there is maybe some people here that can help:

http://www.police.govt.nz/advice/drugs-and-alcohol/drugs-and-alcohol-getting-help

[hotwire 352]

Does have the conventional distributor - however I think the timing is ok as even before doing the head gasket it would rattle, but not quite as often as it does now. I'm thinking it will be compression. Will run 98 from Mobil for my next fill and see if it helps.

Does the b27 have the same compression as the b25? Also when it was pinging did it sound like a rattle from the engine? I've never heard a car ping so i'm not really sure what it is. Very lucky fuel is cheap at the moment!!

Are there any adverse effects of running 98 over 95? It wouldn't be too high would it. Only reason I ask is because I much prefer fueling at Mobil than at Z.

Over advanced ign timing (even by a little) will cause pre ignition. So check/get it checked.

It is NOT at all good for an engine to pre ignite.

Pinging does sound like a rattle when engine is under load at lower speed.

98 is the best fuel for it, certainly not too high. Av gas makes them even better at around 105 ish octain

[Kepes 231]

Over advanced ign timing (even by a little) will cause pre ignition. So check/get it checked.

It is NOT at all good for an engine to pre ignite.

Pinging does sound like a rattle when engine is under load at lower speed.

98 is the best fuel for it, certainly not too high. Av gas makes them even better at around 105 ish octain

Will try 98 and if the problem persists will check timing. Is there a quick way to do this or can it only be done by checking the timing marks on the crank and cams? Probably will be in there again soon anyway to re-tension the t/belt after 600kms.

[BM WORLD 1283]

WTF 91 ,

I never use that in any bmw !!!!!!!!!!!! you just use more fuel when you use a lower octane fuel because you have to put your foot into it more

most bmw's are higher compression engines

always use 95 or higher .

make sure you have zero vac leaks around the intake system.

you may need to get ecu remapped if the compression has been raised heaps

to resort the fueling and timing etc

also the air flow meters go off tune9wear out etc) after years of use and can give wrong readings to the ecu

[Kepes 231]

Problem solved after filling up w/ 98 at mobil!! No more rattle, i'm very glad I didn't have to get into timing.

At only 15c more per litre it works out to be about $6 more than 91 per fill, nothing to be alarmed about at all.

Also, should I be worried about any damage that occurred while running it on 91? I really hope I haven't done anything harmful.

[hotwire 352]

I would always by choice run on 98. We only have 95 locally so 98 only gets used when I am passing a 98 station.

I would still get the ign timing checked, yes it needs doing with a timing light - Simple job. It may still be a tad over advanced. If pre ignition is very slight - it may not be obvious.

I doubt any damage has been caused at this stage.

[Allanw 1071]

I would still get the ign timing checked, yes it needs doing with a timing light - Simple job. It may still be a tad over advanced. If pre ignition is very slight - it may not be obvious.

I agree - just because you can't hear pre-ignition, doesn't mean it isn't there... and it's potentially worse, because you can't hear it, you don't back off the throttle.

Over a long period, it can do damage too.

[will 169]

I would always by choice run on 98. We only have 95 locally so 98 only gets used when I am passing a 98 station.

I would still get the ign timing checked, yes it needs doing with a timing light - Simple job. It may still be a tad over advanced. If pre ignition is very slight - it may not be obvious.

I doubt any damage has been caused at this stage.

Being a 325i, it has the distributor cap fixed on the front of the head. The timing is set by the ecu, it cant be adjusted unlike the earlier 320i/323i which has a conventional distributor on the side of the block. The ecu should adjust the timing to suit lower octane fuel.

Check for air leaks into the intake, check the afm is working correctly, if you have an oxygen sensor, check that it is working. Check that you have the correct spark plugs.

Something is likely leaning the mix out, using 98 is just masking the problem, you need to sort it out what is causing the detonation or it will cause damage.

The best way is to take the car to someone with a rolling road and test it under load, specifically the emissions.

[Kepes 231]

Being a 325i, it has the distributor cap fixed on the front of the head. The timing is set by the ecu, it cant be adjusted unlike the earlier 320i/323i which has a conventional distributor on the side of the block. The ecu should adjust the timing to suit lower octane fuel.

Check for air leaks into the intake, check the afm is working correctly, if you have an oxygen sensor, check that it is working. Check that you have the correct spark plugs.

Something is likely leaning the mix out, using 98 is just masking the problem, you need to sort it out what is causing the detonation or it will cause damage.

The best way is to take the car to someone with a rolling road and test it under load, specifically the emissions.

Really? I thought it would just be the raised compression as a result of having the head resurfaced and also having 325,000km on it perhaps some carbon buildup also contributing to higher compression?

AFM was cleaned a few months ago. Spark plugs are about 1year old and the correct type. Air leak is possible, but car runs great right now. Spark plugs look normal and fuel consumption is surprisingly good so I don't think it is running rich either.

[polley 916]

Being a 325i, it has the distributor cap fixed on the front of the head. The timing is set by the ecu, it cant be adjusted unlike the earlier 320i/323i which has a conventional distributor on the side of the block. The ecu should adjust the timing to suit lower octane fuel.

Check for air leaks into the intake, check the afm is working correctly, if you have an oxygen sensor, check that it is working. Check that you have the correct spark plugs.

Something is likely leaning the mix out, using 98 is just masking the problem, you need to sort it out what is causing the detonation or it will cause damage.

The best way is to take the car to someone with a rolling road and test it under load, specifically the emissions.

M20's don't have knock sensors or any way to tell the engine is pinging or knocking and reduce ignition timing. So if you do run crappy fuel, it will ping/knock and the ECU will not know a thing about it.

[hotwire 352]

Being a 325i, it has the distributor cap fixed on the front of the head. The timing is set by the ecu, it cant be adjusted unlike the earlier 320i/323i which has a conventional distributor on the side of the block. The ecu should adjust the timing to suit lower octane fuel.

Check for air leaks into the intake, check the afm is working correctly, if you have an oxygen sensor, check that it is working. Check that you have the correct spark plugs.

Something is likely leaning the mix out, using 98 is just masking the problem, you need to sort it out what is causing the detonation or it will cause damage.

The best way is to take the car to someone with a rolling road and test it under load, specifically the emissions.

I was under the impression (because I had questioned him early in the thread) that the engine had the standard distributor, hence being able to adjust timing. I stand corrected but I thought I remembered early 325's as not being Motronic.

Agree with your comments though

[Kepes 231]

Apologies for any confusion I may have caused!! I'm still a noob :~)

[hotwire 352]

No Problem, so is it at the front as Will suggests?

[Allanw 1071]

I was under the impression (because I had questioned him early in the thread) that the engine had the standard distributor, hence being able to adjust timing.

Ha - I thought that too. OOps.

Apologies for any confusion I may have caused!! I'm still a noob :~)

We all are - when we think we know everything, someone changes the rules (or you have kids, and they really DO know everything!)