My 1998 K2500 suburban with a 7.4L is rough running. The ICM, the ICM connector,cap and rotor, plugs and wires, ignition coil, fuel filter were all changed with no improvements. The check engine turned off for about 24 hrs and then came on again tonight. It seems to run better and it is cold. The rough running gets worse as the engine heats up. Please help! I'm out of ideas.
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Rep: 449.1k
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366
1.4k
Hi @hobbytrader1 ,
Have the OBDII port scanned with a scantool to see if there are any error codes showing.
If there are it will give an idea of what is happening in the engine.
Have read that AutoZone will do this for free.
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Rep: 703
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The check engine light is key here and should point you in the right direction.
It sounds like you’ve taken care of the spark side of things.
This issue could also be related to fuel delivery, air intake, the fuel/air mixture, or a timing related sensor. Examine the vacuum hose for your fuel pressure regulator. A fuel pressure test may be helpful to ensure proper pressure is attained and maintained by the fuel pump and pressure regulator. Professionally done is best but if you do it yourself take proper safety precautions and have fire control equipment handy. There is also the possibility of a faulty oxygen sensor throwing off the fuel/air ratio, or a camshaft position sensor or crankshaft position sensor negatively affecting the timing.
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