Help troubleshooting overheating/missing cylinder

[amarokorg]

Could use some help troubleshooting my '92 Vert, stock KA24DE engine.

Loaned it to a friend (I know, I know...) and got it back with overheating problems.

First thing I noticed was that #4 was missing. Rough idle, pull the plug wire, no change. Swapped plugs/wires between #4 and #3, and the problem went completely away - all cylinders firing properly. I figured I just had a loose connection or some such that good taking apart resolved.

Friend had run the overflow bottle dry, so I topped up the bottle, radiator and burped the system by opening the bleed screw at the intake manifold and filling until coolant came out. Put it back together, drove the piss out of it for 30 minutes or so, no overheating issues at all.

Fast forward to a few days later, decided to take the Vert on a few errands.

About 10 minutes into driving, it started overheating quicking and badly. Pulled over and let it cool for 20 minutes or so, and started trying to limp it home. Interesting (and probably important) point - while it was overheating, I tried running the heater to draw some heat away from the engine - the heat setting would only blow cold air (A/C switch was off). Long story short, it finally died about 2 houses from a friend, so I pushed it the rest of the way and let it cool overnight.

Came back the next day to see if it would start, and sure enough it would run, but now #2 is missing. Limped it home (about 1.5 miles) on three cylinders and now I'm into it to try and figure this out.

Put new plugs in (it was time anyway), old ones (Bosch Platinum) looked nicely colored except for #2 which was expected since it wasn't firing. No amount of swapping plugs, wires, etc has gotten #2 to fire. I have verified that I have spark to #2 by taking the plug out, grounding it, and turning the engine over - nice blue spark.

Ran a compression test (twice) and here are the results:

Cylinder #1 120, 130Cylinder #2 130, 135Cylinder #3 110, 110Cylinder #4 115, 115

I realize these are pretty low - the engine was cold, and I didn't really want to run it long enough to get it hot on 3 cylinders. I was mostly looking for any serious differences that might indicate a blown head gasket.

So I've really got two issues here - the #2 cylinder and the overheating. Until I get all cylinders firing, however, I'm not really going to be able to do much about the overheating.

For what it's worth, I'm suspecting a stuck (closed) thermostat for the overheating. I've got another one in the box ready to go in once I get this firing thing figured out.

I'm guessing my next troubleshooting step is to try swapping injectors from another working cylinder. Ideas, anyone?

Thanks!

- Dave'92 Vert

[amarokorg]

I decided to go ahead and let the engine warm up on 3 cylinders to get a better feel for the compression. After idling for 10 minutes or so and the temp gauge showing normal running temp (right in the middle), I checked the compression again.

Results were very similar to the cold readings:

Cylinder 1 : 130, 130Cylinder 2 : 130, 130Cylinder 3 : 115, 115Cylinder 4 : 120, 120

This engine is original, as far as I know, and the chassis has about 160k on it, so I'm not terribly surprised that the engine is a little tired. After adding oil to the cylinders, I get the following:

Cylinder 1 : 180Cylinder 2 : 200Cylinder 3 : 160Cylinder 4 : 170

My assessment of this is that the rings are dying - not surprising for 160k. But... that doesn't really help me with the missing cylinder or overheating.

Oops, almost forgot - while letting the engine warm up, I *did* find a tiny crack in the top plastic of the radiator, it was bubbling just enough to be visible. I'm going to get some hi-temp RTV and fix that. Obviously, that could have something to do with my overheating, if it's never able to get proper pressure.

Other ideas?

Thanks!

- Dave

[nissans13240sx]

compression seems alittle low. i think they are supposed to be between 150-170 maybe headgasket is bad. would explain overheating, and possibly why u have a misfire.

[GoinTopless240]

Had similar problem when the marbles in the can syndrome started. I brought it to a shop and then "supposedly replaced the timing chain without pulling the head. I got the car back and they told me now it had an overheating problem. It would seem that they let in run in shop parking lot and it WAY overheated and was told that it had a overheating problem. I got the car back and parked it (had no more money to fix). I had same problems you had with sputtering and not wanting to run. I finally had someone I trusted look at it and the head was warped. Since it was machined no more overheating. I still get the sputtering on occasion, but have narrowed it down to the infamous transmission problem. From the sounds of your compression results I would think you're really low. I would suspect possible head gasket/head issues. I would think if rings were that bad that you would notice some serious oil consumption issues/loss. I did not remember but did you check the oil for possible coolant contamination. Hopefully you can catch it before more damage occurs.. Good luck

[amarokorg]

Not doubting that the compression is low - but in all the headgasket failures I've seen, there'd be one or two (usually two) with VERY low compression indicating a blowout between them with the other two at reasonable (or comparable, anywy) levels.

Also, the fact that there's enough compression for combustion still doesn't help me figure out why #2 is failing to fire.

At this point, if I can get #2 running, I'll putter with the overheating issue and drive this engine until it gives up and then replace it.

Comments?

- Dave

[amarokorg]

Well, looks like the cylinder miss is a bad injector. Got the trusty Fluke out, #2 shows an open circuit, the other three show 10.9-11 ohm as per spec.

Now I just need to find an injector.

Once I've got that fixed, back to the overheating issue...

- Dave