Rep Power: 0

Honda Civic 2000, engine has 15000 miles on it, ran fine previously. Has been sitting since 2001, started and ran engine for 20 mins every 6months. Recently late 2010 began using and found very rough idle at low rpm. Replaced distributor, had no effect on rough idle. Checked signals to pcm, from distributor, fuel injectors, map sensor, etc. Found all signals were ok.
Checked compression on all cylinders and found number 2 considerably lower then all others. Put air hose on # 2 cylinder we find air escaping from air intake. We are assuming intake valve leakage. Computer readout gives a code of 1399 which we understand indicates a random misfire. We are also seeing another code for cylinders #1, 2 and 3 having random misfires.

We administered additive cleaning agents to the oil and gas with no change.

We are aware we will need to address the #2 cylinder issue.

Any ideas what could have caused this low compression issue under these circumstances?

 
Rep Power: 217

I had my old car run really rough one day. Turns out one of my spark plug wires fell out from not being pushed in all the way after a tune up. That probably isn't your problem though. I thought maybe I had screwed something up royally but that's all it seemed to be. You could have a leak somewhere.

 
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Thanks for your input, yes I have checked wiring and plugs. It just seem odd a 2000 yr car with 15000 miles ran fine put in storage until recently, should suddenly have low compression on # 2 cyl.

 
Rep Power: 0

its your intake manifold gasket. does it sound kind of like popcorn coming out the exhaust? i just had the same prob not too long ago. get some throttle body or carb cleaner and spray around the intake manifold with it at idle. if it sucks into it and smooths out the idle for a second, thats the culprit