VIDEO: Not idling, super rough, no power

[lolcantturn]

This is an M20B25..
I've been usually able to diagnose my engine much better than when I first got the car, but this has me stumped.
It doesn't hold idle, and if it does it holds it at 200RPM, then I give it gas past 3000RPM and the engine shuts off.
Its SUPPPPPPER shaky around 2500rpm.
Starting it up is awful (as you'll see in the video)
And I basically have no power.
I DOUBT its a vacuum leak, I put a new intake boot and my ICV's been cleaned well, if its a vacuum leak then it would sure be audible because it would have to be a major one to cause it to die so easily.
I changed out the spark plugs, nothing.
Not overheated, Headgasket was changed 2 months ago so I'm pretty darn sure I have good compression.


Also, prior to this my idle was super perfect and steady at 600rpm..
My guess is a cylinder isn't firing....but I don't know how that can be. There's no arcing between the contact points on the distributor cap

[matias88e30]

Maf? Tps?.... spray some carb/ brake cleaner in al the hoses u see to make sure its not a vaccum leak, also by the intake manifold gaskets..
hope it helps, thats wierd tho.

[lolcantturn]

Maf? Tps?.... spray some carb/ brake cleaner in al the hoses u see to make sure its not a vaccum leak, also by the intake manifold gaskets..
hope it helps, thats wierd tho.

E30's dont have MAF's, I cleaned out the TPS about a month ago. How would I determine a leak from spraying the cleaner? Thanks

[Eecen]

You sure your getting spark at each cylinder?

Do a compression test maybe?
Didn't you not machine the head when you changed the gasket or something like that?


jlevie should be posting some wisdom in a minute...

[jlevie]

Hard to say what the cause of that is, but is sounds like a lot of misfires. Start by pulling the valve cover to see if you have a broken rocker. Then run the static fuel system tests in the Bentley and pull all of the plugs and check each one's spark. Make sure that each plug is firing equally strong. If the spark varies, replace the rotor, distributor and ignition wires and see if that helps.

After that, if the problem still exists, replace the crank position sensor and have the injectors cleaned and flow tested. While the injectors are out run compression (dry & wet) and leak down tests. If all else fails, replace the DME.

Although you can't find an intake leak, that doesn't mean there aren't any. A smoke test of the intake will tell for certain.

[lolcantturn]

You sure your getting spark at each cylinder?

Do a compression test maybe?
Didn't you not machine the head when you changed the gasket or something like that?


jlevie should be posting some wisdom in a minute...

I'm not too sure, but I'll test it. What should I do, hold the plug against the valve cover and see if a spark occurs?
I guess I'll have to do a compression test, I didn't machine my head, but its odd that after 4000+ miles it would fail like this. No overheating or white stuff on my dipstick, no signs of a bad head or gasket..I dunno. Just strange.

Hard to say what the cause of that is, but is sounds like a lot of misfires. Start by pulling the valve cover to see if you have a broken rocker. Then run the static fuel system tests in the Bentley and pull all of the plugs and check each one's spark. Make sure that each plug is firing equally strong. If the spark varies, replace the rotor, distributor and ignition wires and see if that helps.

After that, if the problem still exists, replace the crank position sensor and have the injectors cleaned and flow tested. While the injectors are out run compression (dry & wet) and leak down tests. If all else fails, replace the DME.

Although you can't find an intake leak, that doesn't mean there aren't any. A smoke test of the intake will tell for certain.

A broken rocker would be obvious to spot right?
CPS is fairly new.
Ahhhhhh Not looking forward to removing my injectors and having them cleaned..I surely hope it's not that.

Thanks. I guess I'll get cracking once the sun rises tomorrow :(

[matias88e30]

E30's dont have MAF's, I cleaned out the TPS about a month ago. How would I determine a leak from spraying the cleaner? Thanks

Your e30 doesnt have a AIR FLOW METTER? tps needs to be adjuste not jus cleaned... If u got any vaccum leaks and spray the brake/carb cleaner you will notice that the engine rpms will go higher, it accelerates by it self, if that happens u got a vaccum leak, U can also perform a smoke test but honestly i dont know how.

[Eecen]

MAF and AFM are different things...



Broken rocker would be very obvious to spot. Were you riding the car extra hard before this started happening, bouncing off the redline a-lot? Rockers shouldn't just break out of nowhere if your driving normally.


Clogged fuel injector would make sense..you can get the rail out w/ the intake manifold still on, just get the valve cover off...don't quote me on that though.

edit
An yeah, just pull you fuel pump relay and crank w/ the sparkplug close to something metallic to check for spark

Have fun

[lolcantturn]

MAF and AFM are different things...



Broken rocker would be very obvious to spot. Were you riding the car extra hard before this started happening, bouncing off the redline a-lot? Rockers shouldn't just break out of nowhere if your driving normally.

Eeeeek! You got me.
This curvy road in my town that's usually boring was covered with snow and was abanonded so naturally, I had to drive it. Lots of sliding and bouncing off the limiter. Not only that but this winter and getting stuck in a SHITLOAD of ice patches must have killed my rocker arm. I'll open up the valve cover and check it out in a little, I've been trying to diagnose this for quite a few hours so I'm pooped

[gearheadE30]

fwiw if you're going to slide the car around, you don't exactly have to bounce the limiter.... I enjoy a good slide as much as the next guy, but I have never once tapped the limiter on my M42, and to slide that before turbo it had to be wound out pretty good....but yeah. That sounds like a broken rocker.

[lolcantturn]

fwiw if you're going to slide the car around, you don't exactly have to bounce the limiter.... I enjoy a good slide as much as the next guy, but I have never once tapped the limiter on my M42, and to slide that before turbo it had to be wound out pretty good....but yeah. That sounds like a broken rocker.

I know, I'm new to the whole sliding thing so I was just having some fun.


Also, yeah, when I was revving high right before the car starting having these symptoms, as soon as I let off the gas it shut off just like how you see in the video.

Oh geeze I hope it's not a broken rocker. I'm not mad about it or anything, I just hate that I have to take my head out in 5* weather.

[txtorquemade]

Subd.

Let us know if it was a rocker!!

[lolcantturn]

Subd.

Let us know if it was a rocker!!

Gotcha, heading out now to check it out.

[lolcantturn]

So I went to try and inspect some aforementioned stuff and I've concluded:
1: fuck its cold
2: its REALLY COLD
3: wow its cold
4: It's actually 3*F outside.
5: All rockers are fine..when I'm kind of bittersweet about. I was hoping I was going to find the problem, which I didn't so I'm disappointed, but I'm happy I don't have to take my head off.
6: The hose that goes from the valve cover to somewhere inside the intake manifold is really crackly and brittle...
7: It's cold

[jlevie]

Broken rocker would be very obvious to spot. Were you riding the car extra hard before this started happening, bouncing off the redline a-lot? Rockers shouldn't just break out of nowhere if your driving normally.

Unfortunately that isn't true. I've seen broken rockers on M20's with automatic transmission that probably never saw over 5k (if that) in the life of the car. My theory is that the biggest contributor to rocker failure is a lack of timely valve adjustments. Excessive valve clearance causes impact loading of the rocker and that repetitive stress leads to failure.