Well, as some of you might recall, I did my first compression test last month on my 2000 Maxima. The readings turned out very high, somewhere around 230psi. Afterwards I used SeaFoam, hoping that maybe it'd reduce the readings a little (by cleaning out some carbon). Unfortunately I never got around to doing a followup that next weekend, but this weekend I did. I also changed my spark plugs, as I put coppers in ~30K miles ago, so I figured they're close to needing change. (the gap was wider than .044", in fact it was between .045" and .050", not sure which since my gauge didn't have any wires in between those 2 sizes)

So anyway, earlier today I did another SeaFoam treatment, waiting 10 minutes after dispensing it through the vacuum hose. Surely the compression readings should be lower by now, right?

Nope.

Last time I did my tests with the throttle closed. Today I started off by doing cylinder 1 with the throttle closed, and I got a similar reading as last time--230psi. This was after 12 cranks of the engine. I did all of these with 12 cranks of the engine.
So just for the hell of it, I tried flooring the accelerator and doing it. Got 240 psi. Did the rest with the accelerator to the floor:

Cyl#1: 240psi
Cyl#2: 240
Cyl#3: 240
Cyl#4: 245
Cyl#5: 240
Cyl#6: 245

Interesting. SeaFoam obviously didn't do anything. (to the compression readings, that is...)

BlackBIRDVQ mentioned a theory related to the old SE-Rs ("Slow 96s") where a camshaft flaw resulted in consistently high cylinder pressures, but a loss of ~10FWTQ. (post: http://forums.maxima.org/showpost.ph...45&postcount=8 ) Makes me wonder...

The old compression test thread is here: http://forums.maxima.org/showthread.php?t=328421

 

heh as a side note, I can't find any information through google about this SE-R problem BlackBIRDVQ mentioned...

 

i am going to a compression test on my 2000 this coming weekend, nothing wrong with it but since I am changing the plugs and the car has 110k miiles I wanted to check out cyl pressure anyways.
But, how in the hell do you get the compression tester in that rear cylinder bank??? i can barely get my fingers in there.....can you shed any tips??
I will gladly post my results when am done....

 

Huh? My tester has a decent size hose... I put the hose down in there, try screwing it in (backing it out if it doesn't feel like it's going in right), screw in until I feel a little resistance (O-ring sealing), then put the gauge on top (it's detachable). It's a ~$30 tester from Autozone. I can't see it from the interior, but I'm not really worried about that... (I would be if the reading was low, 'cause I'd want to see how fast the reading rose)

 

yea mine has hose too, but there is so much junk on the way and its almost impossible to see back there, I do like to see the gauge while I am cranking the engine, should not take more than 3 turns of the engine for cylinder to reach peak pressure.

 

ah yeah. I did try 1 cylinder out by cranking it 4 times, looking at the gauge, and it read 210psi. I did it another 8 and it finally read 240psi. I think it actually hits 240psi by the 6th crank or so, after which it tops out.

 

I'm at work right now just messn around on the .org durring my lunch break ( at some bad White Castles in the morning for hang over cure and now I'm hurting ) once I get home I will dig up the info on the Slow 96 club stuff I talked bout.