Shaking under power

[RenoF250]

My truck has just started shaking under power. It is particularly noticeable in D and OD from ~35mph up. Sometimes it will shake with light throttle and get worse. Sometimes it will not shake at all. It can shake enough to make the dash make noise, it is fairly bad.

I first thought driveline - carrier bearing and being that the truck has ~201k and it 12 years old I figured that was a safe guess. I replaced it and all three u-joints but it is still the same.

Bolts holding engine/trans/xfer case all appear tight. Mounts look fine. ATF is red and at the right level.

Engine sounds a little off but nothing obvious I can pinpoint. This last run it was getting stuttering for lack of a better description.

Any ideas?

This isn't a race car, I would think a problem like this would have a pretty obvious cause.

 

[leswhitt]

Mine occassionally does this and at first I thought it might've been the rear u-joint. After researching more on the net, it sounds like it's either a flexplate/torque converter issue or possibly a vibration induced by the engine. I'm still sorting it out with road tests but once I get it narrowed down and/or the frequency with which it does this increases (once every 7-10 days), I'll post up.

 

[RenoF250]

Now it is intermittently running crappy at idle. Has a Injector driver code. Did a buzz test and it says #1 is open. That with the #5 and #7 GP failure leads me to believe it is a bad PS wiring harness. I already bought the harness and the GPs so I guess I need to get to work.

 

[leswhitt]

I think you're on the right track, I found that my shaking increased when I ran thick WMO mixes so it's definitely an injector problem. Right now I'm running regular diesel thinned with a splash of gas with the thought process that hopefully the thin fuel will unclog my fuel system. So far the shaking hasn't returned so whether it's a mechanical injector issue or an electrical injector issue, I think that's what causes the shaking.

 

[War Wagon]

Missing injector was my first thought. That under valve cover harness is often the culprit of these issues. Definitely the first and cheapest direction to go. You're on the right track.

 

[RenoF250]

Pulled the VC and the harness was practically fallen off. Pushed it back on and the GP code cleared but still got P1271. Changed VC gasket and harness and tried it again and it passed twice. It seems to run good now.

I did not clear the codes on the first test, is that possibly why it still was getting a P1271? I had the harness already so it was not a huge deal to put it on.

Now I have to fix the up-pipe leak.