Help Interpreting Compression Test

[Chebyshev]

My '89 325iX is having some very rough idle and stuttering problems when given throttle. I almost didn't make it home the other day, trying to nurse the throttle for the last 1/8 mile or so. I just did the timing betl/tensioner/water pump/etc and this problem didn't show up until after I did that work. That being said it first showed up a few weeks ago and I cleaned the ICV thinking that might be it and it seemed to fix it. Then it started happening again over the last couple days. There's only 137k on this engine (supposedly, relying on the previous owner for that information).

I pulled out the plugs today and did a (dry) compression test using a Harbor Freight compression tester. The results are:

1 - 110psi
2 - 115psi
3 - 90psi
4 - 120psi
5 - 118psi
6 - 120psi

I know those are all lower than the spec in the Bentley manual by about 30psi and the #3 cylinder must have something wrong, but I don't really know where to go from here. Should I do a wet compression test on all the cylinders? Is a leak-down test the next step? Is it possible that I bent a valve in #3 somehow while doing the timing belt?

[McGyver]

...I just did the timing betl/tensioner/water pump/etc and this problem didn't show up until after I did that work. That being said it first showed up a few weeks ago and I cleaned the ICV thinking that might be it and it seemed to fix it. Then it started happening again over the last couple days.

This is confusing. Did the problem show up immediately after the TB change, or several days/weeks after you did the work?

[Chebyshev]

This is confusing. Did the problem show up immediately after the TB change, or several days/weeks after you did the work?

Sorry, that is confusing...

I did the timing belt and then this problem showed up maybe a week later. I then cleaned the ICV because it was only an idle problem (so I thought) and it went away for a couple weeks. Then it came back a couple days ago, except now it isn't just rough and surging idle, but hesitating and almost stalling under throttle.

Could it be as simple as the valves need adjustment? I haven't done that yet since I got it.

[Chebyshev]

I just rechecked the compression this morning before going out to get tools for a leak down test and all that and now all cylinders are at 120. I'm not sure what was going on with #3 yesterday, but I made sure it was fully warmed up this morning before doing it.

It is still running like shit though.

[moatilliatta]

Maybe had grit on the o-ring, or the one way valve is acting funny

Numbers sound low, check your timing marks again.

[Chebyshev]

Maybe had grit on the o-ring, or the one way valve is acting funny

Numbers sound low, check your timing marks again.

Any way to do that without taking out the radiator and all that? Not sure I can see the mark on the camshaft sprocket with just the distributor cap and rotor off.

[moatilliatta]

Depends on how accurate you're trying to be, If you wedge the lower hose to the side, you should be able to see the crank timing mark onto the front timing belt cover. Assuming the hub and balancer are in line with the crank and reinstalled properly.

If running excessively rich, you can wash the cylinders down with fuel lowering your compression numbers, but I'd retrace your steps from the beginning.