RUNS ROUGH WHEN APPLYING GAS.

1998 GMC Sierra

Tiny

muzzleflash120mm

March, 3, 2012 AT 1:19 AM

This happened suddenly, the truck went from having great power and smooth idle. To: rough idle and it feels like the truck is missing on 2 cylinders.(Not positive of this but it feels like that) truck will still start, but when applying gas it gets rougher. So far my thoughts are !Fuel filter. 2. Bad coil pack. 3. Timing slipped a tooth. 4. Bad gas/ water in fuel. (I had just put in gas less than 8 miles before this happened.)

FOUND 4236 RELATED QUESTIONS

Running Rough

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34 IMAGES

Idles Rough/changed Ects

37 ANSWERS
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14 Answers

Tiny

fixitmr

March, 3, 2012 AT 2:39 AM

What motor?

Tiny

muzzleflash120mm

March, 3, 2012 AT 2:55 AM

5.7 ltr. Vortec

Tiny

fixitmr

March, 3, 2012 AT 4:12 AM

It's likely got spider injection which has poppet injector problems make sure your fuel pressure is OK. 58lbs and holds after pump turns off.

Tiny

muzzleflash120mm

March, 3, 2012 AT 4:20 AM

Ok, like I said, it runs. It has a feel like a bronco I had one time. The fuel filter clogged up and it had no power if you stepped on the gas and it felt like it was misfiring.
. This almost feels like the motor is out of balance when you accelerate.

Tiny

fixitmr

March, 3, 2012 AT 4:49 AM

CEL? Codes?

Tiny

muzzleflash120mm

March, 3, 2012 AT 4:52 AM

I will be taking it and having it run on a tester tomorrow. I havent tested it yet to see what codes come up. But I do know that when it fist started this the check engine light was flashing.

Tiny

fixitmr

March, 3, 2012 AT 4:57 AM

Yah that's a misfire CAT warning damage may occur.

Tiny

muzzleflash120mm

March, 13, 2012 AT 3:54 PM

I had the truck tested with an obd II tester. Random misfire was what came up. Compression tests show 150 in all cyl's fuel pressure is good. Possible crank sensor failure? Is it possible that the sensor needs to be shimmed?

Tiny

muzzleflash120mm

March, 13, 2012 AT 3:57 PM

So far I have replaced the plugs, wires, cap, rotor. When first started after replacement the truck ran good. But this was short lived, obd test indicate random misfire.

Tiny

fixitmr

March, 14, 2012 AT 6:54 PM

Is light still flashing?

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