I have a 96 F 350 crew cab with the 7.3. It has 257k miles and does not burn oil. I just bought the truck as it was a deal i couldn't pass up. I changed the oil and filter a few days ago.
The engine has a definite misfire in at least 1 but possibly 2 or even 3 cylinders. I scanned for codes, and found 2. They are 1219 CID stuck low, and 1298 IDM fail.

Here is where it gets weird. If i run the key on engine off injector buzz test, i am getting a pass. If i disconnect injector clips from the valve cover (doesn't matter which one), i still get a pass. Then i can run the key on engine on test and disconnect different injectors and also you guessed it, i get a system pass.

I have disconnected the PCM and the IDM to check for connector corrosion, and cleaned both. I re-ran both tests and the results were the same. I know these era PCMs for the gas models were subject to the leaking capacitors. Are the diesel PCMs subject to this also? I attempted to remove the PCM last night but ran out of time. I assume the wheel well liner needs to be lowered to get the module out.

So the end question, is would the PCM or the IDM be the potential culprit, or does this sound like a combination of failures in both modules?

 

What do the harness plugs to the valve cover gaskets look like? Any signs of melting? The same for the under cover harnesses? The glow plug pins are kind of prone to melting the plug, and if bad enough will melt into the injector pin, causing a misfire. If this happens the IDM can detect this and shut one bank down to protect itself. If you know someone with a 7.3, you can put your IDM in that truck, and if the problem follows the IDM is suspect. There have bee quite a few reports of water in the IDM, which is bad.

 

All of the gaskets and pin connections at the valve covers are in good condition. The wire harnesses under the valve covers have not been inspected yet. I am going to perform an Ohm check of the 8 injector circuits tonight prior to removing the valve covers. If there is a short, i don't want to move the wiring and have it disappear. Unfortunately I don't know anyone with the same model truck that i could have them test the IDM.

I am still ultimately confused on how the buzz test can show a pass on the scan tool with several injectors disconnected.
While troubleshooting my 95 e150 5.8, i did have a few occasions where the PCM would not report codes, but the engine would misfire, buck and hesitate. That problem was caused by the capacitor leakage.

 

https://www.ford-trucks.com/forums/1...load-test.html

ohm out from IDM connector with above link to colored diagram

 

Buzz test is mostly audible. If there was a short somewhere then the IDM would generate a code and the test would fail.
If not already I would change the CPS as that would throw the CID (cylinder ID) failed code and cause missing. Get one from Ford or International dealer only. Correct one is dark gray with a purple o-ring.

 

Thanks for the information. I have the injector circuit printed out and will go though it thoroughly tonight.

So the crank position sensor CPS will cause missing. My RPM tachometer at idle is very smooth even with the missing. I will check it as well however.

 

Jim is correct about the buzz test being audible. You have to stand by the engine with the hood open and listen to each solenoid buzz. Not sure what the scanner is looking at when it says Pass when injectors are disconnected, maybe like Jim says it will Pass unless there's a short, even though the injectors are disconnected.

 

Totally agree on the CPS and good thinking.

I have heard so so many guys say that "When they go out you are walking".

Well, hate to burst their bubble but I have had them intermittently fail countless times. Those things are garbage and thats why everyone should carry and extra with a 10mm wrench in their glove compartment.

Also will add... and I dont know if this applies to a 96...
Disconnect the fuel bowl heater element wire and see if the issue persists. Aftermaket filters can short it and it can interrupt the pcm. It finally will blow the fuse to the pcm if it shorts enough.

This is another one I had guys tell me would be a dead in the water failure but mine hopped skipped and screwed around before finally blowing the fuse.

 

Update. I was able to verify the continuity for the IDM to injector circuits. All wiring is confirmed good. I was also able to check out the PCM. I removed the PCM, opened the cover and all components appear good, no leaking capacitors. The IDM was already out, so i did the shake test. Nothing rattling around inside, no water. What i did notice was on the IDM was a circular disc, about the size of a nickle with a few holes in it on the side opposite the label. The color in the holes was white. I assume this was a desiccant?

I put it all back together and performed the buzz audible test, and i don't get the solid clicks/snap sound like i hear on some videos posted.

So my next step is to locate a crank position sensor and replace it. I have not done the fuel filter, so i am picking one of those up as well. If neither of those help, I think the next step is a set of injectors.

 

Buzz test is NOT a solid clicks/snap sound, just a buzzing sound like a bunch of bee's flying around under the hood. It is completely different than normal injector operation. CPS is the heartbeat of the engine, that being said it's a lot cheaper to try than new injectors.

 

If the injector's ohmed out ok, I would go with IDM first

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That is sort of the pattern the CPS sees.
The issue is when it cant tell the long lows from short to know when its at TDC

 

Update. My local ford dealer had the CPS in stock. The latest version black with purple o ring. The CPS that i removed was a cheap knockoff, so i guess i have a backup now. I installed that. and changed the fuel filter. The old filter didn't look too dirty, but since i don't know the service history, i felt better changing it anyhow. I started the truck and it runs exactly the same. Since there were no codes, for the IDM or PCM, i pulled the trigger and ordered a full set of injectors. They are out for delivery today and it looks like this weekend is going to be very nice to change them. I will keep you posted on the results.

 

The problem is solved. I was able to install the injectors this weekend. The installation was easy with the exception of the number 7 injector. Thankfully it was not bad. What i did find was the number 3 cylinder injector from the tip and up to the first fuel seal was black, and indicated that it was not seated properly. I used a rubber mallet to lightly seat all of the injectors and listen to how it sounded as it seated. The truck runs as it should now.

Thanks for the help.