Mike Sigmond

Hopefully someone can verify this for me but I think you have a bad o2 sensor from what your describing now. When the system closes it begins using the O2 sensor to adjust the fuel/air mixtures.

kruqnut

Maybe the o2 sensor is bad but i think its more than that. If the o2 sensor were bad it's run fine in open loop when the sensor wasn't doing anything anyways wouldn't it?

kruqnut

I ran it throguh an OBD driving cycle or whatever its called, to try to get some codes to trip. I got an EGR insufficent flow error. So I took my throttle body off and cleaned the egr vacuum really good, AND BROKE MY THROTTLE CABLE. Great, lol that oughtta be fun to fix. Anyways I got the passage really clear now so I shouldn't have a problem with that anymore. Heres the data from the code tho:

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Throttle Position - 0.3%

Engine RPM - 1136

Air Flow Rate - 4.67GR/sec

MAP Sensor - 30 KPA

Coolant Temp - 177 degrees F

Short term fuel trim 1 - 0%

Long Term Fuel Trim 1 - negative 13.3%

Short Term Fuel Trim 3 - 50%

Long Term Fuel Trim 3 - negative 45.2%

Vehicle speed - 45mph

Fuel System 1 - closed

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apparently I finally went into closed loop, but my fuel trim doesn't seem any better. I need to figure out why the fuel trim is so off, any ideas?

Mike Sigmond

Ahh, a stuck/dirty EGR. Glad you found the problem. I dont know much about the freeze frame data, maybe someone here can answer that for you. That sucks about the cable, I guess we all win some & loose some.

kruqnut

I haven't fixed the problem, I don't think i've even touched on it. Maybe fixed some error codes, the problem still remains tho

Mike Sigmond

Id get a vacuum guage and test all the ports then. It could be alot of things and I dont wanna misdirect you, I am just trying to brainstorm with you without having my hands on the motor.

kruqnut

Ok the egr system is fixed, I ran a test drive and the I/M monitor says EGR system OK. On my test drive I had no codes but many symptoms. I got out on the road and took off gradually like the GM OBD II drive cycle says, Got up to 55mph and put on cruise control and drove 4 miles or so at 58 mph. I then gradually decellerated down to 20 mph, turned around and this time applied about 3/4 throttle and it was misfiring badly in the 2.5k-3k range, never got higher than that. I then got up to 55mph and re-equipped cruise control, it went a little bit, then it bucked alittle bit, kicking cruise control off. I traveled back to my house then cruised down to a stop at my driveway. It bucked a few more times on the way in.

I noticed that went it bucks the tachometer goes from liek 2.5k rpm down to 2k then flucuates some more before the car stops bucking and missing and settles down to slowly resume acceleration again. any of these driving symtpoms help anyone diagnosing the source of my problems?

jmcan10402

have a 98 monte carlo z34 which has always ran like a champ, but one day at a stop light misfired badly. turned out to be a gasket had failed on intake manifold. the recommended antifreeze/coolant actually eats the gasket and the coolant gets in with your oil. pull spark plugs to confrim. you need a new intake manifold gasket . get a set with metal reinforcements.

Jason