i've been running into random missfires recently. it will run like a champ for a few hundred miles...then out of nowhere start misfireing like crazy.

since it first started i have added longtubes (problem dissappeared for a month..figured it was a glitch), in the process i replaced the plugs and wires.

i have checked all the wires for burns, and proper connection, as well as checked the connector for the coil packs.

i scanned it today and was seeing MANY...sometimes 100s...of misfires on cyl 5, 7 and 8, and a few on 6. was also seeing 1 or 2 on cyl 1-4 but i think that was due to the whole other bank not firing right.

NOW:
cylinders 5-8 are the passenger side correct?

do i replace the whole coil pack, all 4 coils at once...or do i do each one separate?

and where can i get the coils? gmpartsdirect? napa/autozone or dealer only?

 

gonna try a few things...after doing some research

first i'm gonna try swapping the o2 sensors from side to side...see if the problem follows the swap...

next i'll try the coil packs...

if the problem follows a swap of sides....i'll know what the problem is coming from

 

1-3-5-7 are driverside refered to as bank 1
2-4-6-8 are bank 2

O2 sensor shouldn't effect misfires at all as they are after the combustion process.

A miss fire can be caused by
missing spark
missing fuel
improper valve event (collapsing lifter)


Hope this helps.

 

Could be a computer related problem too? The computer controls both the spark and the fuel (injectors). Could be a problem there? I doubt that all 8 coil packs are failing?! Although I suppose anything is possible right??

Am I mistaken, or was there not one of those TSB's (technical service bulletin) or something around 99's that acknowledged some type of electrical or computer problem they had?? It could have even been something with the batteries or connections, but it caused weird electrical issues with 99's. Maybe someone else knows a little more about this?

 

****...this is not good news...

7 and 8 seemed to be misfiring the most...with 5 close behind

and this morning...driving to work (pouring down rain...couldn't ride bike). it started and was doing the normal misfire...1mile down the road it REALLY started acting funny...and the SES light was flashing...which it's never done before. but before i could find a turn off...it stopped and began to run perfectly.

i stopped at McD's for some food...and it started fine...and drove the next 3 miles to work perfectly...NO MISFIRE

what gives

 

o2 sensors tell the computer how to adjust the fuel mixture, so yes, they can cause missfires

however, to only affect 2 of the 4 cylinders on one bank, its most likely not the o2's

 

Double and triple check everything you idsconnected during the header install. If moisture makes it worse you may want to look into stuff like corroded wires or corroded connections. Perhaps some water made it's way into someplace it shouldn't during your header install?

Getting the codes read wouldn't be a bad idea either.

 

well first off...it was doing it BEFORE the header install

second....i have scanning software and can read all the codes AND watch the number of misfires per cylinder


all it's giving me is "random misfire" code not helping much...

i'm gonna go through and clean the O2 sensor connectors and check them, and get some electrical connector cleaner and do the coil pack plugs.

AND i'm gonna call the dealer about the possible TSB

 

This is probably a shot in the dark, but I've heard that the wires to either the fuel injectors or the coil packs (sorry I can't remember which) can get the insulation cut and ground out.

 

since the problem occured out of the blue....long before my header install...or any other major part install...i can't imagine a wire got damaged.

i'm gonna check the coil connections and clean them with contact cleaner...hopefully that helps.

the car seems to be running perfectly for the past 2.5 days...ran like crap monday morning for 2 miles...then ran fine...and has run fine since

 

Tried going back to the stock MAF ends and air temp module yet? Those two mods do not sit well with some cars.

Just more shots in the dark, which is about all you can do with a problem like this.

 

the ATM is off actually...i don't run it in the summer...air is too hot and causes knock i think...

the maf ends i don't think are the problem...been running them on 2 cars without any trouble like this.

and i have tried unplugging the maf...put it into "limp home mode" i think....still does it...so that kindda rules the maf out i think

 

I HAD THE SAME PROBLEM WITH MY 2000 T/A , RIGHT AFTER I INSTALLED AN OFF ROAD Y-PIPE. THE PROBLEM ON MY CAR WAS THERE WAS A TINY WHOLE ON FRONT 02 BUNG AND IT WAS SUCKING IN FRASH AIR AND THROWING THE COMPUTER OFF AND IT WAS ALSO ON 8-5 AND ALSO THE #8 FUEL INJECTOR WAS BAD. SO THAT MIGHT GIVE YOU A PUSH IN THE RIGHT DIRECTION! GOOD LUCK!

 

GUYS GET THIS

i changed the oil today, and while at it i changed the fuel filter

i pulled the old filter off and it was 1/2 covered in undercoating...the same undercoating the car has

now typically undercoating is done when the car is new....

so that means that the fuel filter could very well be the ORIGINAL piece!!

i'm hoping that may have been my problem....maybe low fuel pressure due to clogged filter...definately explain the random onset of the problem...and possibly the random recurrance of it

we'll see