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Discussion Starter #1
hoping to get some help here.

i have a 96 f450 7.3 auto service body with 115k miles. last day or so it has started to randomly run like a model T (best i can explain it). when this happens the check engine light comes on, then just as quick as it came on it might go off and run fine.

i have played with the 4 plug connections on the valve covers. my problem is much like it sounds with one of the plugs undone. my mechanic is convinced that the plugs are the problem, but to me it doesnt seem to change things by wiggling them when it does run rough.

also, the check engine light does not come on when one of the plug connections are removed, but does run rough.

so whats really bothering me is why the plug connections would be the problem if the check engine light doesnt come on when they are removed. when my problem starts, the check engine light immediately comes on.

sorry for the book, just wanted to be clear as i could. any help would be greatly appreciated.
 

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Discussion Starter #2
bump..

i think he will be tinkering with the plugs in the morning while i'm at another job, i'll try to give him a hand after lunch. so i guess we'll figure it out eventually.. just hoping to get some extra help here. thanks.
 

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Early year 7.3's use 2 connectors on each valve cover. Each connector feeds to 2 injectors and 2 glow plugs. What will happen on these is the glow plug connections will burn up, causing issues with whichever injector wiring it's near.

If you check codes it will tell you if this is your issue. Another thing to do is pull all the valve cover connectors and inspect them for melting. Usually it's obvious from the outside, but sometimes they will burn up under the valve covers and you won't see it without pulling them off.

If it melted bad enough it will sometimes melt the engine wiring harness. Ford sells a wiring connector that you can splice in to repair this.

If you do find melted wiring harnesses I would recommend replacing the valve cover gaskets, and both jumpers under the valve cover.
 

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Discussion Starter #5
dude tried it this morning several times at advance auto... "no codes found".

bout right. I just had it fixed up and painted, no more than pulled it out of paint and body and it started this crap. of course they "didn't touch anything". when it happens, it runs like it does with one of the valve cover plugs undone. but check engine doesn't come on when it is undone.. if it happens to, it runs reeeaally rough.
 

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Hmm, well it's probably logged it as an IDM code then. You need a scan tool capable of doing a KOEO (key on engine off) test and a buzz test. These trucks are weird in that IDM codes are logged and stored differently then PCM codes. In order to retrieve IDM codes you have to do a KOEO. In order to clear stored IDM codes, you need to first run the KOEO test, followed by the injector buzz test, then clear codes, This is the only way to clear IDM codes.
 

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I know this is a old post but just wanted to see what the problem ended up being. My truck is doing the same thing. I already replaced the valve cover harness and replaced a burnt pigtail. Still I get the check engine light and runs rough randomly, and clears up and light goes off. Used my Edge programmer to check codes but found nothing, not sure if it checks the IDM codes though? It never stalls, it always seems to work itself out, sometimes takes a few miles and has no power at all. I did notice that if I let off the accelerator and downshift like when engine braking it seems to clear up faster. I am betting on the IPR. But the fact it never stalls make me second guess unless its sticking open rather than closed? Not sure, Thanks,
 

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Did you check the other UVCH?
 

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Sure did, actually installed new UVCH on both sides along with valve cover gaskets and replaced 2 of the pigtails that had some mild damage. With the truck running I can unplug the valve cover harness and as expected the truck runs rough, but the check engine light doesnt come on. When the truck does the random thing the light comes on and goes back off when the truck starts to run good again.
 

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Well, just an update, I found a good used IDM and still having a problem. I have a snapon 2500 that I am going to get to use this weekend to do a few tests. My new thought it that I have a bad injector that shorts out and the IDM to protect itself kills the entire bank? Still looking help if anyone has any other thoughts?
 

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The IDM will do that, but usually it won't be the injector itself. It will usually be the wiring to it (external connector, VC gasket, or under-valvecover harness, or a combination of all of them). Cheers!
 

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Well, just an update, I found a good used IDM and still having a problem. I have a snapon 2500 that I am going to get to use this weekend to do a few tests. My new thought it that I have a bad injector that shorts out and the IDM to protect itself kills the entire bank? Still looking help if anyone has any other thoughts?
If the check engine light is coming on then it's got to be logging a code somewhere. I'd start with figuring out what code you have and go from there.
 

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Ok, Pulled the codes, I got code P0282, which is on the number 8 cylinder. The number 8 cylinder is on the drivers side and that is the side that has been shutting down. I checked all the wireing, replaced the harness under valver covers even moved the wires around while the truck was at idle to try to get it to start acting up again and it wouldnt. I think I must have a bad coil/solenoid on injector number 8 that is shorting out every now and again and causing the driver side bank to shut down. Anyone have a known good solenoid one they would sale cheap?
 

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I found the OBD2 readers (advance auto reader) doesn't read the codes right always. Very frustrating. AE reader with Ford option does as does Dealer. Bit of a bummer.
 

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Ok, Pulled the codes, I got code P0282, which is on the number 8 cylinder. The number 8 cylinder is on the drivers side and that is the side that has been shutting down. I checked all the wireing, replaced the harness under valver covers even moved the wires around while the truck was at idle to try to get it to start acting up again and it wouldnt. I think I must have a bad coil/solenoid on injector number 8 that is shorting out every now and again and causing the driver side bank to shut down. Anyone have a known good solenoid one they would sale cheap?
It's a very good possibility that the solenoid is causing the issue. It's not the most common failure but it can happen.
 

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Sounds good, I have been using a Snap-on mtg2500 scanner to do the testing. I drove the truck tonight and it ran fine, drove 15 miles to the store. Just as soon as I fired it back up to head home it went back to running on 4 cylinders and this time I think its for good because I drove a few miles back towards home and it never cleared up. I stoped and shut her down and unpluged the rear harness to cylinders 6 and 8 and fired her back up and cylinders 2 and 4 came back to life. Atleast I was able to get home running on 6 cylinders rather than just 4. Once I got home I pluged the 6 and 8 harness back in and the drivers side bank shuts down again. Ran a buzz test and all injectors buzzed strong but I still get the code for the number 8 that I had earlier. Tomorrow I am taking the coil off the number 8 injector and swaping it with another from that side of the engine and then running another buzz test to see if the code follows the coil or stays with number 8. I guess if it stays with number 8 that means I will be pulling the harness apart to check wires again. Kinda hope its just the coil. If anyone knows anything I may be overlooking I am all ears!!! And if anyone has an extra coil please let me know. Thanks!!!
 

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swaped injector solenoids between number 4 and 8, ran a buzz test and now everything checks out and I get no codes and truck runs fine. I have a new solenoid on the way, going to replace the solenoid just to be sure. I talked to another guy who said a bad CPS could actually cause the buzz test to fail and most the time if fails on the number 8 cylinder? Doesnt make any since but if the injector solenoid doesnt fix this I guess its worth a shot. I just replaced the CPS a few months back with the dark blue one from ford, the black one isnt available anymore from what I can tell. Any thoughts on the CPS causing issues a P0282 code???
 

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swaped injector solenoids between number 4 and 8, ran a buzz test and now everything checks out and I get no codes and truck runs fine. I have a new solenoid on the way, going to replace the solenoid just to be sure. I talked to another guy who said a bad CPS could actually cause the buzz test to fail and most the time if fails on the number 8 cylinder? Doesnt make any since but if the injector solenoid doesnt fix this I guess its worth a shot. I just replaced the CPS a few months back with the dark blue one from ford, the black one isnt available anymore from what I can tell. Any thoughts on the CPS causing issues a P0282 code???
There have been some issues with the CPS causing a engine running #8 cylinder balance fault, but I've never heard of it causing any issues with the injector buzz or non running tests. I'm thinking you have an issue with that injector solenoid. If it acts up again but has a #4 code in it then you'll know for sure it was the solenoid.
 
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