Light Pinging Uphill: Stock 525i- Any Ideas?

[justme]

Hello- I have a totally stock 95 525i with 120K very well cared for miles.

Symptoms:
- Light pinging when outside temps are above~72 and going up a steep hill @ ~25mph and @ ~2000-2500RPM. Occasionally pings btwn shifts (automatic)

What's already been done:
- O2 sensor
- 1 step cooler plug
- Searched for vacuum leak
- Borescoped
- New fuel filter
- Test fuel pressure
- Reset ECU
- Hooked up to computer while driving... Timing is adjusting
- No errors (ex: faulty sensor)
- Checked running temp... all good
- Running Chevron 91 octane (california crap, but oh well, no choice). Pings MUCH worse with Shell.

Car details:
- 95 325iA with single vanos

Thx!

[JhwShark]

Take a compression test...you indicate timing is OK. Something up with valves is the possibility.

You also mention pings going uphill. Typically, what gear do you put it in when going up hills?? or do you let the car shift on the uphill??

Occasionally pings between shifts...when the car does it's own shifting, such that at the top of the rpm's prior to the shift it pings?? y or n

[justme]

Hey- Thanks for the help.

Haven't done a compression check yet. Will grab the tool and try it.

Gear/Shifting:
In terms of gearing uphill, I usually shift down to Sport mode, thus, I adjust my speed so the RPMs are higher, but stays in 2nd instead of going into 3rd. This usually reduces the pinging a bit (less engine load).

Pinging btwn shifts:
I doesn't ping once its above about 2500. Thus, it usually does the in btwn shifts just when it goes into the taller gear. Then the knock sensors kick in and it stops. But the 1 sec of so that its pinging is pretty strong.

Additional info:
It seems the biggest influence is temperature. The warmer it gets outside, the more it pings (assuming at at running temp. Doesn't ping until the engine is hot-obviously). Thus, I ordered intake air temp sensors and ECU water temp sending unit just in case these are sending bad readings. Also, I once did an excelerator stomp code test and it said engine running lean. Didn't show up when I actually plugged it into a laptop code reader.

PS- Noticed your user name is Shark head... gotta shark by any chance? I'm also in the SF Bay area and have an 87 635. Great car!

Thanks!

[JhwShark]

The lean engine can cause ping'n...but why is it lean? FP is OK, checking compression...injector flow? When you check comp. note the the plugs condition...

I have two Sharks, the original BMW shark the e9 (low production count predecessor to the 635, but the 635 is the common known Shark) and a Porsche 928 (known as Shark in the P crowd...though some of the 911 up-tights don't think the 928 is a "real" Porsche).

[justme]

Hey- Thx again for the ideas...

When I pulled the last set of plugs out, they looked picture perfect. I'm not getting the lean readout any longer from either the gas pedal method or a direct hookup to a laptop for all the codes and such. I'm thinking the one lean code is a red haring.

In terms of injector flow- I'm not really sure how to check that. The closest I came was looking at fuel pressure which was ok. I'll check the compression and see what happens.

Finally a little more observation information... I drove it last night and it was around 53 degrees outside. I heard the pinging. It consistently happens at exactly 2100-2500 rpms no matter what. My VANOS is noisy and I'm planning on a rebuild or replacement. Is there any chance a really noisy VANOS at those RPMs could sound like pre-detonation? My ears are really tuned to the sound of detonation from my days racing drag cars so I'm pretty sure its pinging, but I could be 'Too' tuned into that sound.

Thx!

[JhwShark]

I read about combustion chamber carbon buildup that can cause similar issues. Here is a link to one method...BMW E34 Ping Preignition

Might want to do some more searches.

Not sure about VANOS noises...

[justme]

Hello Again- Sry for the delayed reply.

I used combustion chamber cleaner from Nevada (mopar) since the stuff in CA is not very effective due to emissions laws. I then borescoped all the chambers and they are spotless. Exceptionally clean so I know its not a carbon problem. I was even able to look at the valves they were also very very clean.

Thus, I don't have that many options left. So here's my thinking: Let me know if you think I'm crazy....

1) I'm getting very slight oil buildup in my plug chambers even after changing valve cover gaskets. Electricity is going to take the shortest route so there is a chance the plugs are prefiring. So I'm going to replace and install a new valve cover and gaskets (in case mine is warped). Its a stretch this is the problem, but its an easy fix.
2) Will replace both ECU water temp sensor and intake air sensor since these both influence the level of fuel the injectors spray in (via the ECU). Again, this isn't that hard to do.

If none of these work, I'm pretty much at a point where its looking like either a bad knock sensor (very much doubt it) or a bad ECU. I really don't want to change the knock senors because the whole intake has to come off and then I'm really in deep with hose replacements and such... ugh. Thus, this is pretty much last resort.

Sound or crazy

Thx!

[justme]

Quick update/question-

I pulled a couple plugs list night. There was indeed oil in the chambers. Thus, I'll change the valve cover and gaskets (changed gaskets about 4 months ago) in case the cover is warped.

But take a look at the color of the plug. This looks lean to me, but my experience is more with American V8 race engines so I want to get other's opinions. This plug only has about 5K miles on them. Thoughts?

Thanks!

[Jared at Pelican Parts]

I'm thinking you have a bad knock sensor or MAF. That plug looks like it's not burning anything.

[justme]

Hey- Hmmm... no codes thrown for a Knock sensor, but I have worried this is what it was. Ugh... really don't wanna take the intake off because then I'm in deep with hose replacements and such (not required, but right to do). But I tend to agree... its just got to be a senor (knock or MAF)... was putting my head in the ground over it.

Thx.