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Old May 13th, 2010, 09:49 PM   #1
Kodiak450r
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constant misfire no codes?

my 99 blazer has developed a rather annoying constant misfire under light accel between 1500 and 2300 rpm. it will sputter as if it has a rev limiter. if i press the pedal harder or let it idle it goes away completely. my first checks were cap/rotor since it seems to do this more when wet outside. i replaced all the tune up parts about 20K ago and used quality parts. everything checked out fine.

the part that confuses me is that it will not set a DTC. scanned it and nothing. usually a misfire will cause a SES light. whats stranger is if it does it for more then 30 seconds the lockup converter won't engage for awhile unless i'm in the throttle more. someone told me the TPS is going bad but i've never heard of a TPS causing a misfire. so should i spend the 40 bucks and replace the TPS? i can rule out fuel pressure or clogged cat because it runs fine under moderate accel.
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Old May 13th, 2010, 09:56 PM   #2
ChevyRacer1981
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TPS can screw up so much crap its not even funny.
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Old May 13th, 2010, 10:05 PM   #3
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spray your plug wires with soapy water while running to see if they are arcing, pay attention to how much throttle you are giving it when it happens this should give you an idea if the tps is bad or not, this sounds like its affecting all cylinders, its very possible you are in need for an intake job but start simple.
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Old May 13th, 2010, 10:59 PM   #4
CHVYPWR
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When the coil on my '98 Z71 died, it didn't spring any codes. It sputtered, cut in and out, all without any SES.
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Old May 13th, 2010, 11:30 PM   #5
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Look at the misfire counter on your scanner. Look at the live data while the vehicle is misfiring.

Now if you really have a code reader instead of a scanner, you're fucked.
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Old May 13th, 2010, 11:34 PM   #6
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Excessive carbon buildup/ sticky valves?
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Old May 14th, 2010, 03:09 AM   #7
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the first thing that came to mind for me was a bad coil pack. if its a 5.3. if its a 5.7 then a cracked plug.
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Old May 14th, 2010, 06:32 AM   #8
86scottsdalek10
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heres a question for you.....is this a fullsize or an s10?

the s10's were notorious for the tappet valves sticking in the fuel injection system. They recommend you go to the 2003+ mpfi setup. I dealt with this on two of my s10's and its a 400 dollar problem.

if its fullsize then its probably a coil as stated before
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Old May 14th, 2010, 10:14 AM   #9
Kodiak450r
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they didn't have a fullsize blazer in 1999. alright heres another question. why is it that if i drive the truck for 20 mins or so the problem goes away? and why is it that it only happens under light accel and not under moderate acceleration?. if i get on it it runs strong all the way up. i need to find a OBD 2 scanner to borrow to look at misfire data see if it's all cyl's because thats what it feels like.
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Old May 14th, 2010, 12:49 PM   #10
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oh sorry......i was thinking tahoe. I wish i knew the ins and outs of the problem but all i can say is they start going bad from around 80k on the clock and up. They start intermittent as mine did at 112k and get progressively worse which also starts to plug the cat because of constant misfiring. I had to replace the spider injection assembly and the cat and it ran like a top but ive heard of the distributors and coils causing problems as well. All i can offer you is my knowledge of the problem and my fix..S10forum.com has been a tremendous help to me but it took me a solid 15-20 hrs of research on that site and on the internet to narrow it down.
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