Random misfire in multiple cylinders
05-10-2004, 09:57 PM
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Random misfire in multiple cylinders I first got a misfire in cyl #8 several months ago (right after the warranty expired, go figure!). So I changed the plugs (NGK TR-55's), and checked the wires (Accell race 8.8's). that wasn't the problem. Shortly after I did that I started getting the "cruise control effect" so I pulled the IAC and cleaned it and the passegeway, temporary fix it started doing it again tonite. While I had the hood open I decided to swap the #8 and the #4 injectors, this had no effect on the miss except to cause it to go from a single misfire in cyl 8 to a general random misfire in multiple cylinders. I only get a code at WOT in the higher rpm's 5k and above and its usually just a flashing SES, the light only stays on if I ignore the SES and keep running at wot. I also get a noticeable loss of power between 5-6k rpm's, it lags then kicks back in just a bit before the rev limiter.. usually. I don't KNOW if it is misfiring at idle, but I suspect it is as the idle isnt smooth, its kinda jerky and you can see the motor jerk to the side every 10 - 15 seconds and the exhaust note will stumble, but no codes.
Now for the question... CAN ANYBODY HELP ME?!?!? PLEASE?
P.S. Two other things, This all started occuring much more frequently after my TSP lid install, and I believe it started after I installed my ASP crank pulley.
Please help me, Shawn Hall
Now for the question... CAN ANYBODY HELP ME?!?!? PLEASE?
P.S. Two other things, This all started occuring much more frequently after my TSP lid install, and I believe it started after I installed my ASP crank pulley.
Please help me, Shawn Hall
05-10-2004, 10:24 PM
#2
I don't know if this will help, but it might. All plug wires are not created equal. I noticed that you are running race wires. My guess is that it's some radio frequency interference from the wires. I would go with Magnecor wires. They are real high quality, and you won't have this crap going on. Some of my friends use their stuff exclusively in circle track, because they had some of the problems that you are describing, except they don't have the modern electronics. The class rules won't allow it. I use their stuff. Here's Magnecors' website and a link to a reputable speed shop that carries their products. They have some papers on their site explaining wire quality.
http://www.magnecor.com/magnecor1/main.htm
Thunder Racing sells their stuff, and they're a sponsor.
http://www.thunderracing.com/catalog...d=204&pcid=104
http://www.magnecor.com/magnecor1/main.htm
Thunder Racing sells their stuff, and they're a sponsor.
http://www.thunderracing.com/catalog...d=204&pcid=104
05-11-2004, 02:20 AM
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Is there any way to check computer for possible PCM/wiring faults? It's a PITA, but that was the source of many of the random misfires we diagnosed when I worked in a shop.
Jeff
Jeff
05-14-2004, 08:07 PM
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A blinking SES light is bad, real bad. Means CAT damage (providing you still have CAT's)
I would check plugs again make sure they are not cracked, make sure plug wires have a good clean connection, swap around your coil packs and see if the issue follows the coil packs, could be an ignition control module, could be crank/cam position sensor, could be PCM related, could be a vacuum leak. Take some carb cleaner and while the engine is running spray it around the intake and see if your idle changes, it if does their is your prob, if not, then no vacuum leak.
Lots of variables, I know how frustrating it can be.
I would check plugs again make sure they are not cracked, make sure plug wires have a good clean connection, swap around your coil packs and see if the issue follows the coil packs, could be an ignition control module, could be crank/cam position sensor, could be PCM related, could be a vacuum leak. Take some carb cleaner and while the engine is running spray it around the intake and see if your idle changes, it if does their is your prob, if not, then no vacuum leak.
Lots of variables, I know how frustrating it can be.
05-14-2004, 08:28 PM
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hmmmm....
just a few quik things... coil packs.
and clean your MAF...
there are a few things that you said that are interresting... the code make you look at ignition... however there are a few things to concider...
first is that it only happens a wot . which although it could be a ingition thing points more to timing and fuel.
also you ses blinking says your cats or O2's aint happy another reason to say something on the fuel and timing side aint good...
the reason i suspect a dirty maf is because the effect it would have is giving you pcm bad info on what air is getting in and that would make your fuel curves nutty... which might not be THAT noticable at regualar cruising speed but at what when the rpms come up you could be detonating causing knock module to pull timing making bad power a bad a/f mix will **** off O2 sencers(codes there too) ect ect ect ...
iac was a good guess but that means nothing at wot...
try that
we'll go from there.
just a few quik things... coil packs.
and clean your MAF...
there are a few things that you said that are interresting... the code make you look at ignition... however there are a few things to concider...
first is that it only happens a wot . which although it could be a ingition thing points more to timing and fuel.
also you ses blinking says your cats or O2's aint happy another reason to say something on the fuel and timing side aint good...
the reason i suspect a dirty maf is because the effect it would have is giving you pcm bad info on what air is getting in and that would make your fuel curves nutty... which might not be THAT noticable at regualar cruising speed but at what when the rpms come up you could be detonating causing knock module to pull timing making bad power a bad a/f mix will **** off O2 sencers(codes there too) ect ect ect ...
iac was a good guess but that means nothing at wot...
try that
we'll go from there.
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05-14-2004, 08:40 PM
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O.K. Jaberwaki, I will try cleaning the MAF again (that was one of the first things I did when I first got the 'cruise effect'). Does anyone have any reason I shouldn't use brake and parts cleaner for that?
05-14-2004, 08:48 PM
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Originally Posted by Ought1-Z28
O.K. Jaberwaki, I will try cleaning the MAF again (that was one of the first things I did when I first got the 'cruise effect'). Does anyone have any reason I shouldn't use brake and parts cleaner for that?
05-14-2004, 08:51 PM
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I am just trying to think of what I have on hand, zamboxl. How about GunScrubber? It dries with 0 residue and will strip carbon off anything.
05-15-2004, 02:11 PM
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OK took it to the dealer and had them put the tech2 on it. Cyl 8 was the worst with well over 2000 misfires and except for cyl 1, all the other cyls. had between 28-200 misfires. We looked at some other stuff and my LTFT table was blank, as in no LTFT. Ray, the service manager who did this, said he needed to have a tech take it for a test drive with the tech2 to see what was going on. I will get back with more info next weekend, I am going to Ft. Cambell, KY for most of this week, so I wont be able to do anything with the car untill next weekend.
