No more oil leak, but...

[SilverSHO]

I fixed the oil leak! A new oil pressure sender solved the problem. I'm still getting down and looking under the car every time I park.

It's still got other issues that I can't figure out, though.

I have a problem with constant backfiring through the exhaust. I don't know where it came from, but my dad suggested that some of the valves may be burnt. A check of the cylinder balance revealed that cylinders 1 and 3 are weak.

According to my dad, if the exhaust valves in those cylinders are indeed burnt, the valves would not seal properly, and some of the exhaust gas would seep out and somehow cause the incessant backfiring.

In other news...other codes indicated that the rear O2 sensor indicates rear bank lean; PIP failure; and SPOUT circuit open. I know about the PIP and SPOUT codes, but how could the car be running lean when the exhaust is slightly smoky (grayish in color, LOTS of smoke when I rev the car at a standstill) and smells strongly of unburned gas all the time (cold and warm)? I had figured that it would be running really rich, especially with the bad gas mileage. I'm baffled.

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Nick
Lt. Titanium 90 135k
Coneless, ACCEL 8.8 stainless steel wires,
SHO Shop torque limiters, Cherry Bomb Turbo II mufflers
AIM: loudog6491, TitaniumSHO

 

[Rob94]

Hmmmmm....if the O2 sensor is reporting a lean mixture, perhaps it is being overcompensated for???

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Rob
White 94MTX
K&N Filter otherwise stock

 

[fredhurderjr]

Check for an exhaust leak near the cats / resonator area. The pipes are very hot, you have some unburned fuel, and when you rev it, then let off, you could be sucking nice cold fresh air back in through the leak, which then ignites (instant backfire).

My backfiring was significantly worse when I had a hole in the cat-back on the driver's side 90° bend, before the rear split.

 

[SilverSHO]

I know I need a new donut gasket between the y-pipe and resonator, but I looked under the car about a week ago and noticed that in addition to the oil leak (now fixed), one of the y-pipe to resonator bolts was missing! I replaced it with a spare I had, and the exhaust is quieter now and backfires less. But even at idle, without revving it, it backfires. Not loudly, just pops spaced one to three seconds apart.

I also know that my brother accidentally snapped off one of the manifold studs to which the y-pipe bolts, and I hollowed out the cats; I was thinking these also could cause the backfire.