7.3 - Random rough idle and power loss

hlb3 · Dec 13, 2015

I have been having a strange random issue with my truck (2000 F550), while driving down the road the check engine light will come on and it will start running really rough and it will lose power. It is totally random, it has happened anywhere from 10mph to 60mph, in 30* temp to 95* temp. When it happens, if I shut the engine off and start it back up the light goes out and it is back to normal. It isn't doing it consistently, it did it the first time back in July, then it didn't happen again for a month or so, then it happened 4-5 times in the last 2 months. Since I had a new spare CPS sitting in the glove box I tried changing that, but it did the same thing the next time I drove it. I also changed the fuel filter in October with no improvement.

When researching it, everything seems to be pointing to a loose plug on the UVCH as a cause, but it looks like everybody that has had the problem, the rough idle/low power problems are constant and not totally random and occasionally or cured by turning the truck on and off like mine.

I'm not really looking forward to pulling the valve covers to check since it is kind of a PITA, so I figured I would post and see if anybody else had any easy things to check first. :awesomework:

crash2 · Dec 13, 2015

Valve covers are easy

DHR Darren · Dec 13, 2015

Also check the ICP & IPR sensor plugs for oil.

dfowlkes · Dec 13, 2015

Does it store a code?

hlb3 · Dec 13, 2015

I went to my buddy's house and got these. Looks like I need to clean or eliminate my exhaust back pressure sensor. After I got home and did some reading on the P1316 and it looks like I should have ran a buzz test to get the IDM codes, so I will have to try to make it back down there next week and test it again.

79chevy39.5's · Dec 14, 2015

Tubes probably broke or clogged. But since it's random probably a harness. They're easy and cheap

DHR Darren · Dec 14, 2015

Have you looked at the underside of the engine harness where it rubs on the valvecover?

zukkev · Dec 14, 2015

Yes, Valve covers are easy, and if that's ll it is, it'll be a cheep fix (with a couple tiny zip ties)...The other mentioned concerns are potentially valid. Check them. And check the main harness connector for looseness (top of driver valve cover); If these are not snug (the bolt holding the halves together), you can get random IDM codes, due to connection issues...You could also be simply dealing with a faulty IDM...Not the first time I have seen that.:awesomework:

crash2 · Dec 14, 2015

DHR Darren said:
Have you looked at the underside of the engine harness where it rubs on the valvecover?

Thats right--driver side front...:awesomework:

hlb3 · Dec 14, 2015

Thanks for the tip about the harness! There was a shiny spot on the valve cover, I unhooked the harness and there was one strand of one wire exposed. I repaired it with some liquid tape and wrapped the whole thing with some more electrical tape and hooked it back up. Not 100% sure if that was the problem or not, from what I found online, it was an injector wire, so it is possible. Having such a small amount of wire exposed could definitely explain randomness of it happening. So I'll keep driving it and we will see what happens.

DHR Darren · Dec 14, 2015

Good work!:beer:

I have repaired all of my 7.3's there and wrap that section in a piece of heater hose or neoprene to prevent further chafing.

crash2 · Dec 14, 2015

I see a wire strand there for sure--nice find...:awesomework:

Toyota_corey · Dec 19, 2015

http://www.powerstrokehelp.com/

theres some really common issues this guy addresses with 7.3's on his site, learned a couple little tricks from him for mine:awesomework: