MISFIRE, O2 SENSOR, AND RPM PROBLEM

Pontiac Firebird

Tiny

trowbridge04

February, 18, 2007 AT 2:35 PM

I have a 1997 Pontiac Firebird V6 3.8L 99,000 mi. One of the problems I'm having is that I keep getting trouble codes saying the O2 sensor bank 1 sensor 3 has a problem, and also I believe it says cylinder 2 misfire. I bought a new O2 sensor and had the repair shop put it in and also change out the spark plugs.

The car ran fine and the light stayed off for about 2-3 days and now it is back on with the same trouble code. It usually comes on when the car is started and is not 'actively' moving. As long as I start driving right after it is started its fine, but if the car is started and say I have to wait to get out of the parking lot, the engine starts spuddering and shaking and the check engine light comes on.

This problem has been dramatically reduced since the new plugs and O2 sensor, but it still happens every once and a while.

Another issue (I dont know if they have to do with each other or not) is when I am driving the car, and am driving anywhere over approx. 2500 rpm, when I shift into neutral, or just put the clutch in, the rpms fall VERY quickly to about 500 or so rpm (this causes the voltage meter to drop) and then it jumps back up to where it should be around 1100 rpm.

What could be causing these problems? Thanks!

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2 Answers

Tiny

kin chan

February, 18, 2007 AT 3:51 PM

Okay.U've got a professional problem in hand. Lets be honest with each other 1st. So maybe we can shine a li'lo lite and trouble shoot problematic area. But true fix still sounds like it require a real professional to take care and verify. 97' is an OBD2 carwhich means on GM it is equipped w/misfire protocol. Now. Do u know what criteria an rear O2 sensor suppose to behave? Or what turn on a misfirecode.O2 sensor at the back suppose to stay steady as an infer value to monitor the catalytic convertor. As for misfire. Concern. When the differentiation of crank and cam spd detected a certain % different on any particular cyl. Then the code will come on as either a single cyl or random misfire cyl code. Lean/rich misfire(fuel ctrl), mechanical brokenengine cpts or ignition cpts can cause a misfire code. As to find out why that cylinder is misfire.U need a mechanic with real OBD2, scope and 5 gas training, equip and experience tonail down the cause. It aint cheap. But
it is a much more skillful demand than an electricain or plumber. Good luck. Letmeknow if any other info I can provide that u are not clear

Tiny

Jack42

February, 19, 2007 AT 8:01 AM

How about the plug wires? When the resistance in the spark plug goes up over time the wire takes the abuse, at that mileage I would install a set of OEM wires and go from there. The miss could also be a bad injector, but do the wires first to eliminate spark as the problem.

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