# 98 Maxima 3.0l engine problem



## rpmaltima (Jun 24, 2008)

So first off, thanks in advance for your opinions!

My car had a crack in the radiator which enlarged, and finally gave up completely. The problem is my girlfriend was driving it, didn't notice it overheat until it spun a rod bearing. Long story short, I took the engine out, put a rebuilt crank with matching rod bearings, everything seemed to be ok.

When I took the flywheel off, I failed to mark it. I looked at it and it seemed symmetric, but now I'm not sure if it has some magnetic marks that I failed to see. I saw two little pieces of metals welded to it, but I figured those were balancing weights from the factory.

So I put the car back together, and after troubleshooting vacuum hoses that were cracked, it idles kind of rough. Not horrible, but noticeably bad.

When I drive it, half the running time it acts like it doesn't have enough gas, hesitates, then all of sudden catches back up and you feel the power as it should be. When it hesitates, if you press the gas too much, it backfires, and you hear them. Let go of the gas, press it again it acts normal, then does the same thing again.

So far this is what I've looked at:
- grounds (all seem ok)
- new crankshaft sensor (ref) cause it was throwing the code for it
- vacuum hoses (no visible problems)
- timing (done it twice, it's hard to mess up markings)
- new spark plugs
- new fuel filter
- new air filter
- cleaned up the EGR valve

I'm out of ideas.

I have a code reader that can graph several engine parameters. The spark advance seems fishy to me at idle, it jumps randomly between 8 and 19 degrees or so. What does that mean? At higher RPM it's stable. I also looked at TPS, it reads linear with respect to pressing on gas. O2 sensors also seem ok from the graph (sine wave'ish).

The ECU is throwing off two codes:
- Knock sensor bank 1 sensor 1
- random cylinder misfire

What bugs me about this, is that it sounds like something mechanical, but the randomness of drivability is weird - so maybe electrical? Some sensor or valve solenoid?

Any input would be very much appreciated, I'm out of ideas


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