Compression tested at 100 PSI, dry, with very small (1 - 2 PSI) deviation between cylinders. The plugs were very clean. Intake manifold and MAT sensor was wet with oil. The MAT was not coked. Power seems low with poor acceleration. Engine has less than 71,000 miles on it.

This compression seems very low to me but I've not been able to find spec on it. What compression should I be seeing?

Do I have bad rings? Burnt valves? Bad guides? I'm puzzled as to how compression could be so low but be so evenly matched between cylinders.

Any input would be greatly appreciated.

The actual results aren't usually as important as the relative compression between cylinders. 100 psi is a little low, but (assuming the test was done correctly) getting close readings (1-2 psi deviation) would indicate that there likely aren't any concerns. Having said that, it's important to do both wet and dry compression tests. Start with the dry test, then repeat the test adding about a tablespoon of oil into each cylinder before hooking up the gauge. If the compression gauge indicates an increase after adding the oil, the piston rings are worn. If the readings change little or stay the same, the head gasket, a valve or valve seat is faulty.

quote Originally posted by Neils88: The actual results aren't usually as important as the relative compression between cylinders. 100 psi is a little low, but (assuming the test was done correctly) getting close readings (1-2 psi deviation) would indicate that there likely aren't any concerns. Having said that, it's important to do both wet and dry compression tests. Start with the dry test, then repeat the test adding about a tablespoon of oil into each cylinder before hooking up the gauge. If the compression gauge indicates an increase after adding the oil, the piston rings are worn. If the readings change little or stay the same, the head gasket, a valve or valve seat is faulty.

Thanks for the input Neill. I'll try a wet test tomorrow.

Compression should be checked with all spark plugs removed, and the throttle wide open. (I just stuck a ratchet extension down in the throttle body, to hold the butterfly open.) Remove the fuel pump fuse to test.
I let mine (also an 88) hit three compression strokes on each cylinder. I saw ~140 lbs on all cylinders. Tested dry.
The strange thing is, I still don't have enough compression to stop the car from rolling, when parked on a hill. I must use my parking brake.

[This message has been edited by Raydar (edited 08-12-2018).]

[QUOTE]Originally posted by Raydar:
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Compression should be checked with all spark plugs removed, and the throttle wide open. (I just stuck a ratchet extension down in the throttle body, to hold the butterfly open.) Remove the fuel pump fuse to test.
I let mine (also an 88) hit three compression strokes on each cylinder. I saw ~140 lbs on all cylinders. Tested dry.
The strange thing is, I still don't have enough compression to stop the car from rolling, when parked on a hill. I must use my parking brake.

Thanks, Raydar about the reminder regarding the throttle being wide open. I completely forgot about that.
The only car that I ever had that wouldn't hold itself on a incline was a '58 VW and it had seriously burnt valves.

I finally got around to running a better compression check. Throttle wide open and 10 ml of oil in each cylinder. Following are the results:

,
Cylinder 1 Dry 110 Wet 130
Cylinder 2 Dry 110 Wet 133
Cylinder 3 Dry 115 Wet 135
Cylinder 4 Dry 110 Wet 128

Looks like I have worn rings/cylinder walls. I did not pass a recent smog test because of high Hc. I don't know if this plays into that problem. Doing the compression test was part of trying to find out what caused that to happen

Maybe cause you fail but likely is iffy cat and/or ECM sensor(s) or wires to them.

Example: ECM O2 uses 2 wire setup w/ tan "ground" to a tran's bell bolt on engine.

I would clean/fix every ground and power end in the engine bay then look for other problems. coat end that get wet bolted to engine etc w/ silicon/brake grease.

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