Sick 7.3. Out of ideas - PowerStrokeNation : Ford Powerstroke Diesel Forum
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post #1 of 12 (permalink) Old 05-19-2017, 03:14 AM Thread Starter
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Sick 7.3. Out of ideas

Hi guys, I hope someone can help me out here.
I'm working on a 2000 f650 with a 7.3 that is dropping the left bank injectors. On startup it usually runs fine, maybe for a few seconds, sometimes a few miles.
Then it will drop the left bank and check engine light comes on with a ef signal code, I can't remember the code number, 1668 maybe?
Anyhow I've done the diagnostic procedures for that code and out tells me to replace the pcm.
Can the pcm cause just one bank to go dead?
I've replaced the idm, harness under valve cover, valve cover gasket, all left bank injectors and removed the loom and tape from the entire wiring harness from valve cover to idm, to pcm. Not a bad spot anywhere.
I've ohmed the entire harness as well.
I can't duplicate the problem by wiggling the harness.
Totally random, one key cycle it might run great for 10 minutes, the next it might start missing immediately.
It always passes the buzz test

Should i toss a pcm at this thing or would I be wasting more money?

Sorry for such a long post, I'm just lost on this one.
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post #2 of 12 (permalink) Old 05-19-2017, 04:02 AM
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Re: Sick 7.3. Out of ideas

Have you considered taking it to a shop? Maybe just let them diagnose it, then do the work yourself.

Jamie.

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post #3 of 12 (permalink) Old 05-19-2017, 04:15 AM Thread Starter
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I am the shop lol. We do mostly class 8 trucks though, so I don't have a great deal of experience with the smaller stuff. We did have a guy from a Ford dealership come look at it but he didn't really have an answer either.
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post #4 of 12 (permalink) Old 05-19-2017, 12:33 PM
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Re: Sick 7.3. Out of ideas

Don't ya hate it when that happens?. im not much of a 7.3 guy either. ive only worked on a few of them and never anything under the hood. I will agree its strange that its calling for a pcm when your dropping a whole bank, yet the idm is what controls the injectors. Flow charts blow don't they? I take it you guys dont have a labscope? That's really what ya need at this point.

Does it miss right away or does it take a while? Is it random or pretty steady after it starts?

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post #5 of 12 (permalink) Old 05-19-2017, 01:02 PM Thread Starter
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Re: Sick 7.3. Out of ideas

Yes it's strange, sometimes it will miss after a few seconds then the next key cycle it might take 5 minutes.
But once it starts missing it won't clear up till you shut it off and start it up again.
My boss is about to lose his mind on this one, but I don't want to waste more money on it.
It is what it is though lo.
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post #6 of 12 (permalink) Old 05-19-2017, 01:30 PM
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Re: Sick 7.3. Out of ideas

Man, thats a tough one. Tell your boss you need a labscope in the future. Without a scope, it's going to be tough to say definitively if the problem is electrical or not. And even tougher to tell if its pcm or idm. Also you would want to check the cam signal when it happens, but a volt meter won't be good enough because the signal will change when it misses and the meter won't tell you if it's a cause or an effect. Again, you'd need a scope for that.

But if an entire bank drops at the same time then it has to be electrical. Also if it misses, then runs fine after shutting of and starting, it's electrical, and not likely to be a wiring issue. Wiring can cause intermittent issues, but it's really rare in my experience. Usually the wiring is either good or it's not.

I hate throwing parts at stuff, but sometimes we dont have a choice do we? If I were going to throw anything at it, it would be an idm before a pcm. Since the pcm timing signal is just one wire, i think anyways, it makes more sense that the idm is the culprit. You could always try a heat gun on the idm and see if it acts up more, but since it's so random in nature, I'm not sure that will tell you much, but maybe. Get it hot and see if the behavior changes. But if we have to put our money on a part right now, I'd go with IDM. Sorry I can't help more than that.

Edit: just thought of something. Scan it and watch the pulse widths when it happens. That will tell you definitively if it's a command issue or not.

Jamie.

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post #7 of 12 (permalink) Old 05-19-2017, 01:39 PM Thread Starter
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Re: Sick 7.3. Out of ideas

The idm is new, that was the first part I tossed at it. I might try a cps just because I'm running out of other ideas. I'll let you know how it goes.
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post #8 of 12 (permalink) Old 05-19-2017, 11:07 PM Thread Starter
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Re: Sick 7.3. Out of ideas

Cps didn't help, found a loaner pcm. Gonna try that Monday.

Last edited by Steeler; 05-20-2017 at 02:43 AM.
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post #9 of 12 (permalink) Old 05-22-2017, 04:17 AM
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Re: Sick 7.3. Out of ideas

Did you look real close at the 42 pin connector for burned pins or corrosion? Also the PCM and IDM connectors, how do they look?

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post #10 of 12 (permalink) Old 05-23-2017, 02:55 AM Thread Starter
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Re: Sick 7.3. Out of ideas

Pins all looked good and clean. I tried wiggling and twisting every connection from firewall to idm to valve cover with no change.
Today we were able to get ahold of a used pcm off of a junk pickup.
I know it's not correct for this truck but it was good enough for a test.
We ran the Heck out of it without a hiccup. That got rid of the ef signal code and the truck ran great. Still not sure how the pcm could cause one bank to die but I've ordered a new one.
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