Group Effort Diagnostic on M30

[Heysüß]

Symptoms:
*Loss of torque*
*Sounds like a suppressed/muffled machine gun/old lawn mower*

The sound changed from an open rumble to this muffled sound, could an exhaust problem really cause this loss in power?

Just happened over night, drove it last night at 10, sounded fine.

Does need a valve adjustment but that was already needed before this.

Thanks again R3V Nation for any input!

[MR 325]

Do you have a cat? Clogged? Check the exhaust flow out the back.

I don't know, just throwing that out there.

[Heysüß]

Wow

I didn't even think of doing that easy check before sending it to the muff shop (;

[Garageaholic]

You have 89 posts - Don't be a wiseass.

Check your engine codes.. .

Test your oxygen sensor. . .

Check for a vacuum leak. . .

Check your AFM . . .

Check for Fuel consumption. . .

Check your ECU. . .

Check your ignition system. . .




Check your engine.

[Heysüß]

I actually wasn't being a wiseass, I really hadn't thought of that, I really am a noob with these cars. this is my first BMW period, I came from a 98 chevy s10 that I drove since high school, and all the problems I had with that were easy to point out. (Alternator, head gasket, egr pipe, cracked downpipe, fuel pump, etc.)

This thing really does have me stumped. But thanks for that check list. And no I didn't do the swap, I bought it like that.

And yes there is flow but it matches the machine-like sound that the engine is doing.

[bataangpinoy]

oh my.

how roughly does it rev, and are there any other noises from the engine?


my m20 did this but it was a snapped rod.

[Heysüß]

I hope that's not what it is.

And it sounds really really rough. Still driveable but it lost all its oomph, I get my bentley back tomorrow so ill start on it then.

[bataangpinoy]

rocker, or rod.

im telling you, my m20 JUST did this. thats why im doing my m30 swap.



it can be alot of things too.

try:
distributor cap
rotor
ignition wires
fuel injectors
fpr
spark plugs

[325isStephen]

had an m20 do the same thing, ended up being broken rocker arm. Pull your valve cover and take a look.

[Heysüß]

Well pulled the valve cover and to my untrained eye everything looked to fall in line ok. Nothing looked warped and the cover didn't show signs of scrubbing.

Guess I'll move on to the spark plugs and wires. See how that goes.

[Heysüß]

update and a Question.

I found the 6th spark plug wire was twitchy so I bought a new set and waited while they came, plugged the new set yesterday and problem persists.

Question:

When checking the distributor and rotor what should I look for ?

I am planning on taking the radiator off and checking it out sometime today or as soon as possible.

[yert315]

look for excessive wear on the metal contacts - inside the cap and on the rotor.

Did you hear any noises when the symptoms started (other than the constant "machine gun" sound)? I must say, this issue sounds mechanical rather than ignition related

[Gadea]

this issue sounds mechanical rather than ignition related

+1
Could it be worn out timing components such as chain or tensioner/rail?
(hope not)
keep us posted of your progress

[Heysüß]

No clue yet but I now know for sure it's cylinder 1 and 3 misfiring. Checking fuel rail side tonight.

[jonmon6691]

I had an SHO that did something similar to this, it turned out that the catalytic converter had broken apart and was clogging the exhaust. I only suggest this because I couldn't tell that was the problem before I removed the y-pipe and actually heard it rattling around inside.