strange sound from engine bay, advice??

[mrclam]

Hi everyone,
Lately under hard acceleration in 3-5th gear in low rpms, my engine has been making funny rattling noises that almost make me think the motor is sucking up tiny rocks in the intake. it only happens in low rpms(<3k) and is not always consistent. it will usually goes away if i accelerate hard a few times. does anyone know what this might be? I had the vanos changed....6 months ago so I would hope it isn't that again. Thanks!

[MauiM3Mania]

Hi MrClam,

Perhaps you could try some high octane gas (a bit of racing grade mixed in with your 92 stuff)...

You may be feeling the effects of CA's lower octane of premium grade fuel.

Scott

[John in Houston]

I agree.... low RPM situations where there is alot of load on the engine (hard acceleration from 3rd, 4th or 5th from low RPMs) is a key place to get detonation. Especially with the crappy LE fuels they are producing now.

Try a higher grade and see what that does. Also, pull your plugs and check them. If you've been detonating alot, your plugs are probably showing it... and need to be replaced.

John.

[mrclam]

thanks guys! i guess now is the time to get those NGK plugs

[fast4d]

what brand of gas are you using?

try unocal 76 gas. They are suppose to be mtbe free already so you're less likely to know/detonate.

run a bottle of redline fuel sys/injector cleaner.

[mrclam]

UPDATE: i changed my plugs to the NGK's spec'd for e46 m3s. detonation is still there, tried 76 gas, detonation still comes back, my next step will be to try 100 octane with ca's mix of 91.


on a side note, while i was tightening a bolt that ties down one of the ignition coils, i manage to snap it from overtorqueing it. is this likely to cause a problem? the ignition coil is still firmly in place and the other bolt is doing its job. if this isn't a good temporary solution, i'll probably go get one of those kits you can use to take out the remains of the bolt and buy a new one and put that in, if you guys could give me advice on that i'd appreciate it, thanks!

[MauiM3Mania]

Originally posted by mrclam
is this likely to cause a problem?

Manufacturer's don't use parts/fasteners unless those pieces are needed.

Get an 'easy-out' to remove the broken stud and replace it. Although there may be no problem, you'll feel better and no doubt will exist as this as being a problem.

You would do well by placing a torque wrench on your Christmas list! :

Scott

[mrclam]

indeed, i actually had a torque wrench with me, but it was rated from 30-1xx lbs, so i doubt it would've helped. i didn't think i had the bolt on that tight, and i was careful when torqueing down the spark plugs, but i guess i should've been more careful. i can get one of these kits at home depot yeah?

[MauiM3Mania]

If you work on your car often, a pair of torque wrenches may be a good idea. One for the 'big' numbers (ft. lbs) and another for the smaller fasteners.

Just my opinion, but I'm not impressed with the tools at HD. Decent tools can be had at good ol Sears, including torqe wrenches.

Best of luck, dude.

Scott

[John H]

Originally posted by MauiM3Mania
Just my opinion, but I'm not impressed with the tools at HD. Decent tools can be had at good ol Sears, including torqe wrenches.

Which torque wrenches do you guys prefer? the cheap ones with a needle that points to the torque figure, or the more expensive ones with a twist-grip that clicks when you get to the right number? i was considering getting the more expensive kind, but wanted to know if this was worth it and not overkill (i have one of the cheaper ones and it seems like a real POS to me, but maybe i don't know how to use it right).

Cheers,
John