Need some help with rough running
Thread Starter
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Tuned
Joined: Dec 2008
Posts: 342
Likes: 5
From: San Diego, Tx
Need some help with rough running
I've got 194k on the truck and have recently started having a problem with it. Itinitally, I was having some vibration at various speeds that seemed to coincide with about 1500RPMs. Going a little faster or slower would make it go away and I thought it was driveline related but that doesn't seem to be the case. Now it's changed and when I start the truck cold (it was 45* this morning, not super cold), it romps for a second before the idle smoothes out and then runs like a complete slug (not the normal sluggishness before warming up). In the 1200 - 1700 RPM range, the truck shakes so badly it feels like the front end is going to fall out. Once it gets up to normal operating temperature, everything clears up and it runs like a champ.
My thought is that I've got a bad/failing injector that is not firing until the truck gets warm but I don't know if that's really the case or how to go about testing it. Any help you guys can offer is appreciated.
I have the orignal CPS and have had no problems with it and I have not done the UVCH fix yet but I would think that if it was a harness problem it wouldn't go away when warm, right?
My thought is that I've got a bad/failing injector that is not firing until the truck gets warm but I don't know if that's really the case or how to go about testing it. Any help you guys can offer is appreciated.
I have the orignal CPS and have had no problems with it and I have not done the UVCH fix yet but I would think that if it was a harness problem it wouldn't go away when warm, right?
Post Fiend
Joined: Mar 2007
Posts: 26,966
Likes: 50
From: Texas
If the truck is shaking that bad, it sounds like UVCH. If the plug is a little loose you can have a bad connection when cold, but as things heat up the connector seats a little better so you're back running right.
Does it sound like it's not firing on all cylinders? Does the CEL come on?
Does it sound like it's not firing on all cylinders? Does the CEL come on?
Thread Starter
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Tuned
Joined: Dec 2008
Posts: 342
Likes: 5
From: San Diego, Tx
I can't really describe the sound it makes when it starts shaking, it's very wrong though. The CEL does not come on. I guess I should pull the valve covers and check the connectors and ohm the injectors? Anybody have some decent instructions for pulling the covers? I'm sure I can get them off without any but I'll probably end up disassembling a lot more of the truck than I need to.
Thread Starter
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Tuned
Joined: Dec 2008
Posts: 342
Likes: 5
From: San Diego, Tx
I messed with it some this morning with AE. With it cold (about 65* outside) I did an Injector Buzz Test and they all sound about the same. Fired it up and it's idling like normal, let it warm up enough and ran teh Cylinder Contribution Test and it passed. Not really sure what's going on with it, I hate intermittent problems.
