• We’re currently investigating an issue related to the forum theme and styling that is impacting page layout and visual formatting. The problem has been identified, and we are actively working on a resolution. There is no impact to user data or functionality, this is strictly a front-end display issue. We’ll post an update once the fix has been deployed. Thanks for your patience while we get this sorted.

'91 Civic oil on plugs 2 and 4

J

jana519

Senior member
I'm rebuilding my 91 Honda Civic CX. I pulled the plugs and there was oil on plugs 2 and 4. 1 and 3 were both completely dry. I can't help but think that means something. I don't believe the rings are worn. The car has only 150K miles but the previous owner did neglect the shit out of it. I'm wondering if perhaps the valves are burnt. Engine seems to run pretty good except for a very small backfire/misfire. Any ideas?
 
jana519 said:
Does a leakdown test pinpoint the problem, or does it just give compression numbers in general. I will try this.



Hmm yeah, definitely possible. Any idea what leads to bad valve seals? Wondering if there's some problem that needs to be rectified.
Click to expand...

A leakdown test is pretty much the opposite of a compression test, it tests how much the cylinder is leaking not how much pressure it is making.

EDIT TO ADD: make sure piston is at TDC when doing leakdown test, obviously, as you want the valves closed.
 
jana519 said:
Does a leakdown test pinpoint the problem, or does it just give compression numbers in general. I will try this.

Hmm yeah, definitely possible. Any idea what leads to bad valve seals? Wondering if there's some problem that needs to be rectified.
Click to expand...
Bad valve seals are usually just wear, possibly accelerated by insufficient oil change frequency. A common symptom of that is excessive blue smoke upon startup, after sitting for a while some oil has drained down into the cylinder.

You can get so-called "high mileage" oil that has a seal swelling additive in it, but you only want to use as much of that as necessary because swelling the seals too much including those that don't need it, will cause more wear. In other words it's perfectly fine to mix the stuff with another non-high-mileage oil.

The real question is what you meant by "rebuilding" it. If you mean that you're (at least mechanically) restoring it with the hopes of getting a lot more miles and years out of it, you may need to swap the engine, or have the head(s) rebuilt if the compression #s look good otherwise. On the other hand, it could just be a leaking head gasket which is something closer to DIY territory and the cost of gasket(s) and whatever else seems prudent to replace while the top end of the engine is off. Then again, maybe you're up for rebuilding a whole engine, we don't know the scope of your efforts or the time frame and budget, but generally a crate rebuilt engine is the way to go for someone not experienced in rebuilding.

With the intake manifold off you should be able to see how bad the valves are gunked up, or to a lesser extent with a borescope which can also be used to do a (poor) inspection of the oily cylinders but not so much looking backwards from the 'scope, at the valves, yet in those oily cylinders you can see how bad the buildup is.
 
Last edited:
You must log in or register to reply here.

TRENDING THREADS

Back
Top