Misfire on all cylinders on one side

[Skyline]

Originally Posted by SlickGT1

No I know how the leakdown test works, my logic is something else. He should be burning oil and smoking with bad rings.

I'm not sure of that. First of all, burning synthetic does not make nearly as much smoke as conventional oil. Second, the cats can clean up quite a bit, (ultimately ruining them of course).

Clearly, with black plugs, oil is getting into the cylinders. If it were leaking through the valve seals, the car would most likely smoke quite a bit at start up.

But bad seals in themselves would NOT cause low compression. The leak down test is done with the valves closed....so bad valve seals could not influence the result; unless you are getting air out the exhaust or intake AND the valve covers, (either the oil filler on the passneger side or the brather on the driver's side). So if air is getting past the valves, then it could potentially make it back into the head through the seals.

[mrathell]

I thought the black residue on the spark plugs were carbon deposits due to the bad fuel/air mixture.

[SlickGT1]

The problem is that he is not adding any oil.

So if he is burning it, how is his level still fine. The plugs do display signs of oil though. But he had leaky VC gaskets, so that is really a moot point. He should be blowing a puff of smoke at startup.

Right, we are hoping he did the leakdown correctly, all in TDC.

Get another mech to take a look at the engine. Something is not adding up.

[mrathell]

Yeah it looks more and more like its time to throw in the towel because I don't want to invest more money into a car that may or may not run properly.

I don't mind doing the work myself but a mechanic is only going to charge me a ton of money for research and may end up with the same results.

Not in a million years am I thinking I know even a tenth of what you guys know but it seems to me that:

- bottom end piston rings would result in burning oil: not happening

- bad valve seals could mean low compression without burning oil BUT the low compression would continue even when I accelerate. Going up hills or anything that required more torque would cause for me to bog out due to low compression: not happening

- if it has low compression, wouldn't it run worse under load? The engine requires more horsepower unload right? So wouldn't the performance get worse while driving because of the compression issue?

Lord knows I could of made many mistakes in my testing, so even if we go with the notion that my data is flawed do to user error, I think certain things should be ruled out due to the facts of how the car is behaving now and only focus on the things that could result with my profile:

Facts:
- The car isn't burning oil
- the oil and antifreeze is NOT mixing
- the misfire on all driver side cylinders go away when rpm's are over 800
- the only codes being returned are for misfire
- the misfire codes go away while driving

To me it seems the direction should be: What would allow for the cylinders to get compression at 800 rpm's but not at 600 rpm's while idle?


Sorry guys, just a little frustrated after tearing down this engine and still clueless.

[Skyline]

Try cleaning every ground point you can find on the engine.

[SlickGT1]

It's a bit mind boggling.

Shot in the dark. Might be an avenue worth looking into. Check the vacuum pump. Is there a vac pump on these 4.4s.

Ground is also something to check.

[mrathell]

There are four heavy gauged rubber coated wires that bolt to the heads. Two on each head. They are bolted directly To each head under the intake manifold. They are visible in the photos on #63 of this thread.

Can anyone confirm if those are grounds.

[TwinTurboGTR]

Those are the knock sensors.

[bastereo]

Guys, rabbit trails!

He has low compression on 4 cylinder and misfires on those cylinders. That is the problem, end of story.

While it is unlikely that his rings are bad without burning any oil, its not impossible. There are 3 rings on each piston. 2 compression rings and 1 oil ring. I bet they all have specific purposes...

I had a much longer response typed into my phone, but it didn't post...

Short story, I have seen the leakage causing misfire at idle before, both times were valves, but they only missed at idle and acted fine off idle.
At idle everything moves slower and there is more time for the compression (air/fuel mix) to leak out, once the engine is spinning faster there is more air and fuel in there (the throttle is open) and with everything moving faster the time it can leak out is smaller so the leakage is a smaller percentage.

How the previous owner managed to kill the compression rings on one side, that's crazy...

[SlickGT1]

Originally Posted by bastereo

Guys, rabbit trails!

He has low compression on 4 cylinder and misfires on those cylinders. That is the problem, end of story.

While it is unlikely that his rings are bad without burning any oil, its not impossible. There are 3 rings on each piston. 2 compression rings and 1 oil ring. I bet they all have specific purposes...

I had a much longer response typed into my phone, but it didn't post...

Short story, I have seen the leakage causing misfire at idle before, both times were valves, but they only missed at idle and acted fine off idle.
At idle everything moves slower and there is more time for the compression (air/fuel mix) to leak out, once the engine is spinning faster there is more air and fuel in there (the throttle is open) and with everything moving faster the time it can leak out is smaller so the leakage is a smaller percentage.

How the previous owner managed to kill the compression rings on one side, that's crazy...

That is exactly what I keep thinking. I still don't think it is the rings. I have a funny feeling the timing went, or it needed guides. Someone dropped the ball, the valves kissed. Or maybe someone manually turned it over till the valves kiss, this would take some effort though. Figured they messed up and stopped.

Why not check a few junk yards, and get a new engine? Probably be cheaper then RR the current heads.