7.3 rough idle after up to temp - Ford Powerstroke Diesel Forum
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Old 07-07-2010, 01:04 PM
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Unhappy 7.3 rough idle after up to temp

2003 f350 7.3. Truck runs great when cold but once it warms up it gets a rough idle. The truck hitches slightly when taking off from a stop light when left to coast ahead on its own without touching the fuel pedal. Last night the truck just died and the cam postion sensor was bad. Changed the cam position sensor. Truck works but still rough idle when warm. Got a scan tool and you can see the cylinder balance is good when cold but once hot about half of them are off by 1-5% and the other half are fine. Does anyone have any ideas? No fault codes found.
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Old 07-07-2010, 01:14 PM
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Check the UVCH on the side that reads funny. You may have a loose connection or corrosion.
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Old 07-07-2010, 01:20 PM
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UVCH? Sorry new to the 7.3 world
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Old 07-07-2010, 01:42 PM
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Under Valve Cover Harness. Your wiring for the injectors run thru the valve cover and the connector sometimes gets messed up.
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Old 07-07-2010, 01:58 PM
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Thanks. Will I need any gaskets or any wear items that should be replace when I do this?
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Old 07-07-2010, 02:02 PM
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pull the plug from the valve cover side. OHM the injectors. The outer 2 pins on each side is the glow plugs. The middle is the common. SO thest the 2 pins on each side of the center. SHould be no more then like .6 i think it is? SOmeone will chime in here. I think theres a write up on it. Its not hard.
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Old 07-08-2010, 01:31 PM
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Ok no luck with the OVCH. Put truck on computer and have all kind of data but have no idea what is good or bad. I do see the coolant temp is reading -40. Changed out sensor and it is still reading -40. Anyone have any new ideas. The #6 and #7 on the balance test is the only ones not reading anything when up to temp now. All are reading 0 when cold. Any help would be great.
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Old 08-03-2010, 03:57 PM
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Update

After taking the truck to the Ford doctor (waste of money) They said the first thing to do was to replace the #8 injector because it was comming up failed. Replace the injector and went down the road. Within 10 min it was found out that it didn't fix the problem it made it worse. Meaning they replaced it with a 1-7 and not an #8 which makes a cracking noise plus the hitching is still there. Took truck back and service manager and he laughed at me. No S**t. The next week took it to another Ford garage and found out that there is a bulletin out. The new CPS will cause the problems that I am having and there isn't a fix as of yet. Nice!!!!! $750 Nice!!!!!! (new injector)and the Big Blue Oval guys are supposed to know their trucks. Not all dealerships are up on there trucks.
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Old 08-03-2010, 04:25 PM
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its not neccessary to have an AE injector in the number 8 hole. It will run quieter but wont cause hesitations or issues(1-7 are AD injectors). When the new grey cps causes phantom codes, its usually throws cylinder 3 and number 8 injectors. (both together) You can get a international cps, part number 1807339c92. It will be blue and help it run smoother and quieter. Its not good to use this if you are running a tuner. But if stock it will be better.
I had a similar issue on mine.
Pay attention if its weorse at say 1/4 tank? If so you need to do the "hutch mod"
Its possible at 1/2 tank too.
Also check the injector wires at the main harness plug at the top of the drivers valve cover. Theres a 10mm bolt that bolts the harnesses together. IT then bends to the inside of the motor. It will push against the bottom and side of the valve cover.(the issue is, injector wires are on the bottom. I had them pushing on the cover and arcing when it got hot. These wiresbend down and then do like a 90 degree to the other side of thr motor. At this bend its forced against the cover. The plastic cover can break or wear thru the wires. Might check here. ALso ohm all wires at the valve cover....
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Old 08-05-2010, 07:23 PM
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I've had a similar rough warm idle problem for the last year, I am going nuts trying to solve it. I have tried all 3 of the CPS's and am now running the original black, and although this solves the cylinder contribution issue on 3 and 8 it did not change the idle whatsoever. I have a new IPR, new ICP, new injectors. I'm still using a fair amount of oil (prob. 1 qt every 1000) and have my rough warm idle. Different tunes from different companies (DP-tuner and BDP) haven't made a difference either.
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