SOLVED: Half-power, bucking, 500rpm idle, won't rev past ~5K

[hwy84]

How little play should the vibration dampener have when bolted to the crank? <snip>

When I watch it spin with the car idling - It appears to be pretty out of round, maybe by about 3mm.

The answer is none. I know this because I investigated more, and found that my crank bolt wasn't even finger tight!! Not good. That's where the looseness stemmed from.

I removed it, loctited, and torqued to spec (hooray for manual transmission! I can just leave it in 5th, pull the ebrake, and chock the wheels to get the 300Lb/feet.

Now to replace the belts and see if a difference has been made...

[hwy84]

No change after tightening the crank bolt and thus locking down the toothed wheel.

Also replaced CTS, and spark plugs with Copper Bosch Supers. No change.

HOWEVER:

I did notice when I came back from my little test drive, that there was a lot of oil on the heat shield above the front exhaust manifold, smoking away. It was wet with oil after a 5 mile drive. Clearly my valve cover gasket is bad... maybe it's the world's biggest vacuum leak, and the easiest fix ever? (seems unlikely)

I'll keep posting as I find more, just for future reference if nothing else.

[itsonlygeorge]

I had a timing issue when I bought my car. The timing was retarded (back one) by one tooth, ran like shit and had trouble with keeping a stead idle especial in cold weather. Did not rev well and felt sluggish and lopey. Ran much better when I fixed the timing and replaced the belt.

Your out-of-round or wandering vibration dampener could be worn main bearings leading to crank wander.

[uturn]

How's the rockers and the cam? Flat spots? Leak down and compression test.

[hwy84]

I had a timing issue when I bought my car. The timing was retarded (back one) by one tooth, ran like shit and had trouble with keeping a stead idle especial in cold weather. Did not rev well and felt sluggish and lopey. Ran much better when I fixed the timing and replaced the belt.

Your out-of-round or wandering vibration dampener could be worn main bearings leading to crank wander.

This is great information. I've read a bunch of threads where the timing belt was one to three teeth off, and the car ran fine - but maybe those were all advanced, not retarded... in any case I'm going to be tearing into the timing belt next.

[hwy84]

How's the rockers and the cam? Flat spots? Leak down and compression test.

[Updated - the compression test below was done cold. When performed on a warm motor, with the throttle open, compression was nicely centered around 145-150.]

Cam looks good, and rockers are in good shape. I adjusted the valves yesterday - all the intake valves were loose, and all the exhaust valves were tight - with the number 4 cylinder being g the worst by a pretty big margin.

I ran a compression test as well - though my compression tester has seen better days ( the O ring is very tired) and got:

1 - 125
2 - 120
3 - 125
4 - 125
5 - 120
6 - 130

Seems okay to me. Low, but I think that could be my tester. I'm just glad they are within 10%.

[hwy84]

Also replaced the valve cover gasket, and torqued to spec. (The valve cover HAD been torqued down so hard, I had to really muscle those little 10mm nuts to break them loose... stupid.)

The oil spew remains. I fear the valve cover is warped. However, spraying carb cleaner around it while idling resulted in no change.

I have another set of used injectors, as well as a water pump and timing belt kit. Those are my next two experiments. I'm really leaning towards timing - it just seems to fit the symptoms so well. I want to also do further inspection of my vibration dampener to see if maybe someone welded it back together without lining up the teeth correctly... long shot, but that's how it feels.

Thanks so much for all the advice and continued attention!

[uturn]

I just hope they didn't do a head job where they skimmed the head too much that you can't get the timing back without using a thicker gasket or adjustable cam sprocket.

[hwy84]

I just hope they didn't do a head job where they skimmed the head too much that you can't get the timing back without using a thicker gasket or adjustable cam sprocket.

Hadn't considered that possibility! High compression FTW? :-?

Hopefully once I get the timing covers off, I'll be able to see if there's enough room on the tensioner adjustment to get any slack out if indeed the head has been shaved.

Not going to progress much this week - too much work, and I won't have much time for the car. But I will report back when I make more progress...

[Kershaw]

That compression is pretty low. My e30 is all 160-170. I would do the injector swap before the timing belt because injectors take 30 minutes to do and a timing belt takes a few hours.

[hwy84]

That compression is pretty low. My e30 is all 160-170.

145 is supposedly "correct."

I am hoping my low numbers are due to tester variance/bad sealing ring on the tester, and not internal problems.

The tester I used was quite tired. I was mainly looking to make sure I didn't have a totally toasted cylinder, or any major differences.

I'll come back around with a better tester if the injectors and timing don't make a difference.

Thanks!

[packratbimmer]

You tested fuel pressure, but did you test fuel delivery. Is the tank clean? Filter fresh and not clogged?

[hwy84]

Well, turns out my compression is actually low - I used the same gauge on our other 325is, and it read 165. :(

Also, my timing belt is perfect - and looks new and beautiful. I was hoping it would be a couple teeth off, and that would explain it, but no joy.

I am replacing the injectors with other used injectors, because I have 'em. I may order some refurbished ones off of the 'bay, cause they are cheap.

I used an endoscope to look into my cylinders, and I am not sure I saw "i" pistons in there. Kind of look more like Super Eta to me. Might explain the low compression numbers, and the poor running, if it's an Eta bottom end and pistons with an 885 head, but now I am just getting paranoid.

I didn't test fuel volume, because the car runs best at WOT between 5500-6500 RPM, when it theoretically needs the most fuel. It runs worst at part throttle, low RPM.

Could be just a tired engine, with leaky/non-atomizing injectors...

Last thing I'll do is start checking all the ECU pins to see if the harness is FUBARed... and if those check out... I think this motor might be pulled and replaced.

But it's late and I still have to button up the motor. So more later.

[hwy84]

The drama continues...

So, the different used injectors made no meaningful difference.

Swapped cap and rotor for known good ones. Perhaps a slight improvement in top end power (5K to redline), but could be my imagination.

Unplugged the O2 sensor and drove it - generally the same, with slightly more more backpopping and backfiring. And a CEL, of course.

I can smell raw gas when I park the car after I drive it with the new injectors, so I suspect at least one is leaky. Given that it makes no difference from the previous injectors, I imagine those were leaky/not-well-controlled as well, which seems to confirm my guess that this is a rich condition, and not a lean one.

Also - could be my imagination, but the whole exhaust system seems hotter than I am used to in my other M20 cars. Perhaps also a symptom of rich running?

I have refurbished injectors coming this weekend. I will also be testing the ECU pinouts to make sure the harness is good, and a buddy from a shop is willing to let me hook it up to his diagnostic computer that might tell me something...

[itsonlygeorge]

Did you check the ECU? What are the odds its an 027 ECU from an ETA and hence the 5500 rpm rev-limiter? It sounds like you may have an eta/seta block with an i head and that might be the cause of your issues.