omg my m20 sounds like a subaru... part 2

[NC325iC]

Driving my e30 to work yesterday pulled off the highway and came up to a stop sign. I left the stop sign in first gear and decided it would be a nice time to let my 3.0L sing and ran it up to ~6000rpm. Heard some weird noises and all the sudden she sounds like a subaru.

My immediate thought, remembering a thread with a similar title to this one from years ago, is that i have broken a rocker arm. So after work i have the car towed home.

Just pulled the vavle cover to figure out which one it was. And they are all pristine and look brand fking new.

So... What else should i check?

Im gonna give the whole engine compartment a good look over for anything that is obvious. Ill change the oil and look for large metal chunks of sadness as well.

[e30trooper]

fouled plug? Mine does that ever month or two ( one cyl has bad rings )

[NC325iC]

not a bad thought, just went to pull the plug wires to check to see those and the #6 wire seperated from the cap. New plug wires are needed. I'll be sure to update the thread once I can replace them.

[E30_fiend]

I was going to say check your plug wires haha.

Other than that, I would focus your attention on just the ignition system as a whole. Spark plugs are cheap, change em. As well as the cap, rotor and wires. All in all youd be looking at like $250-300 in parts but your ignition system will be good for quite some time so long as the motor is running correctly. If you buy a new set of plug wires, you will probably never need to buy another set for as long as you own the car. They are very resilient pieces.

Do all that and check back. I still think it was the plug wires haha. Your thought process is the same as mine. I first thought broken rocker because I have been there before.

Good luck!


Taylor

[NC325iC]

Tell that to the set that I pulled off with ~30k miles... I'll order a new set as I would bet that's the problem. I'm a bit relieved.

Come to think it was prob more like 15k miles...

[e30construction]

does it feel like its slipping when your put the pedal to the floor?

[Cabriolet]

if you havent figure it out. you have bad compression in 1 or more cylinders. i know the sound you are talking about. because it's happened to me.

[NC325iC]

Continuing on now. Plug wires didn't help just bought a compression gauge. Pulled the plugs. I'm leaning toward the bad cyl being #5. Here they are.

[NC325iC]

1: 180
2: 180
3: 180
4: 90
5: 80
6: 178

Approximately. I'd say likely a headgasket btw 4&5, right? I mean that's kinda best case.

[E30_fiend]

That would be my guess. The less likely issue could be a cracked head or block between those two cylinders. Even less likely than that is cracked valve guides on both those cylinders.

How did you check compression? Hot? Cold? how many cranks on the motor?

[NC325iC]

Very cold. 4 cranks. Dry

[E30FreaK89]

Also check that all of your plugs on the injectors are clicked all the way down! After replacing my broken arm my m20 did it again! I was freaking out thinking i broke another rocker arm.. Turned out to be one of my fuel injectors wasn't plugged in all the way... Ran good after that!

[Cabriolet]

Approximately. I'd say likely a headgasket btw 4&5, right? I mean that's kinda best case.

this is a blown HG. get the head resurfaced and pressure tested. and do valve guide seals while it's off. best of luck