Problem Still Around...
#1
02-02-2008 | 07:11 PM
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Problem Still Around...
So as some of yall know ive been havin a ongoing misfire problem. I have had it in a few shops after xmas, including a tranny shop (just to rule it out) They told me the tranny was fine, but i was havin a misfire under full load. They ran a compression test and found the #7 cylinder wasnt holding compression. Took it to another shop to have them work on it, they ran 2 compression tests (called it a "wet" test) and said everything was fine. No cracked head, all the valves were fine. I had him check my wires, plugs, cap and rotor just to rule those out as well, all fine. They couldnt find a reason why it was misfirein. they did an induction service (yeah i know i could have done it my self but my mom offered to pay so why not) and it didnt do much.
some other factors is when coming to a complete stop at a light, the rms drop really low and you cant hear the truck running. the rmp needle sits about 2 cm under 500 mark. in park it idels around 500-600. maybe idle air conrol going bad?
ive checked the plenum, its fine. So any other suggestions fellas? maybe coil goin bad?
some other factors is when coming to a complete stop at a light, the rms drop really low and you cant hear the truck running. the rmp needle sits about 2 cm under 500 mark. in park it idels around 500-600. maybe idle air conrol going bad?
ive checked the plenum, its fine. So any other suggestions fellas? maybe coil goin bad?
#3
02-02-2008 | 07:24 PM
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#5
02-02-2008 | 09:45 PM
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RE: Problem Still Around...
ORIGINAL: motorbrreath
So as some of yall know ive been havin a ongoing misfire problem. I have had it in a few shops after xmas, including a tranny shop (just to rule it out) They told me the tranny was fine, but i was havin a misfire under full load. They ran a compression test and found the #7 cylinder wasnt holding compression. Took it to another shop to have them work on it, they ran 2 compression tests (called it a "wet" test) and said everything was fine. No cracked head, all the valves were fine. I had him check my wires, plugs, cap and rotor just to rule those out as well, all fine. They couldnt find a reason why it was misfirein. they did an induction service (yeah i know i could have done it my self but my mom offered to pay so why not) and it didnt do much.
some other factors is when coming to a complete stop at a light, the rms drop really low and you cant hear the truck running. the rmp needle sits about 2 cm under 500 mark. in park it idels around 500-600. maybe idle air conrol going bad?
when
ive checked the plenum, its fine. So any other suggestions fellas? maybe coil goin bad?
So as some of yall know ive been havin a ongoing misfire problem. I have had it in a few shops after xmas, including a tranny shop (just to rule it out) They told me the tranny was fine, but i was havin a misfire under full load. They ran a compression test and found the #7 cylinder wasnt holding compression. Took it to another shop to have them work on it, they ran 2 compression tests (called it a "wet" test) and said everything was fine. No cracked head, all the valves were fine. I had him check my wires, plugs, cap and rotor just to rule those out as well, all fine. They couldnt find a reason why it was misfirein. they did an induction service (yeah i know i could have done it my self but my mom offered to pay so why not) and it didnt do much.
some other factors is when coming to a complete stop at a light, the rms drop really low and you cant hear the truck running. the rmp needle sits about 2 cm under 500 mark. in park it idels around 500-600. maybe idle air conrol going bad?
when
ive checked the plenum, its fine. So any other suggestions fellas? maybe coil goin bad?
an IAC only affects engine operation at IDLE. off idle is not affected.
#7
02-02-2008 | 09:58 PM
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#8
02-02-2008 | 10:13 PM
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#9
02-02-2008 | 10:25 PM
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RE: Problem Still Around...
ORIGINAL: motorbrreath
thanks for the replys guys... i took the throttle body off and cleaned it and all the parts when i did the plenum check. the mis happens when im accelerating.
thanks for the replys guys... i took the throttle body off and cleaned it and all the parts when i did the plenum check. the mis happens when im accelerating.
what code is the OBD 1 scanner throwing? have you verified correct fuel pressure? are the injectors clean? just for giggles, switch the #7 plug and plug wire with a different one. see if that casuses that cylinder to misfire.
#10
02-02-2008 | 10:27 PM
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RE: Problem Still Around...
The PCM uses the IAC motor to control idle speed along with timing to reach a desired MAP during decel to keep the engine from stalling.
When the engine rpm is above idle speed the IAC used for....
Off-idle dashpot (brings RPM down slow after the throttle blades close)
Deceleration airflow control
A/C compressor load control
Power steering load control
The IAC could be you idle problem, But the misfire is a whole other story.
Are you sure it's a misfire? Is it throwing a code for it? How's the coolant and oil levels looking? Could it be possible that you could have a bad head gasket?
Odds are that if you have low compression on the #7 cylinder that may be your misfire problem.
When the engine rpm is above idle speed the IAC used for....
Off-idle dashpot (brings RPM down slow after the throttle blades close)
Deceleration airflow control
A/C compressor load control
Power steering load control
The IAC could be you idle problem, But the misfire is a whole other story.
Are you sure it's a misfire? Is it throwing a code for it? How's the coolant and oil levels looking? Could it be possible that you could have a bad head gasket?
Odds are that if you have low compression on the #7 cylinder that may be your misfire problem.