97 7.3 power loss, rough idle - Ford Powerstroke Diesel Forum
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Old 08-13-2008, 02:50 PM
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97 7.3 power loss, rough idle

No codes. recently changed lift pump, and cam sensor. Now she idles up and down from 500 to 700 rpm. some loss of power, and in neutral, I can rev to 2000 rpms and let off and engine will stall. But will crank right back up. Any Ideas?
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Old 08-13-2008, 03:09 PM
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i had a similar problem a few months ago. Ended up being that my Injector Driver Module (IDM) was dying. try disconnecting you ICP sensor to see if there is any change. the IDM is a Ford only part, the IH version won't work.
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Old 08-13-2008, 03:22 PM
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you should check the fuel filter, and clean the screan on the side of the bowl. its on the fpr
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Old 08-13-2008, 05:51 PM
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I am thinking that it very well is the IDM. The filter is brand new.....second one in two weeks. The strange thing is that I have cleaned that little screen on the side of the filter housing 3 times and every time it has had a good bit of trash on it, so I cleaned the entire pressure regulator, not much inside though.. Could the IDM be going out without throwing any codes?
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Old 08-31-2008, 04:02 PM
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Same exact problem

I have emailed Mountain Synergy buy no reply.

Did you come to a resolution on this one? I have am haveing the same exact problem.
-idle is stable sometimes but for the most part will continue to oscillate up and down from about 1000rpm down to about 250rpm.

-it will die sometimes when coming to a stop. The idle will drop and not recover in time so it dies.

- I unplugged the ICP sensor and all it did was raise the idle high enough that it wouldnt die as easily. With the ICP unplugged it would raise the idle but while coming to a stop the idle would still drop to a point it almost dies but would pick itself backup a little sooner so that it wouldnt die.

- I just changed the oil too. A long while ago the truck would take about 2 blocks to accellerate to 45mph even at full throttle. it would sputter and miss until it finally got up to speed and from then on everything would be fine. this was only first startup. I changed the oil and that fixed that problem. I thought maybe it could be a factor this time too. Guess not

-I dont really want to change the crank position sensor because the tachometer seems to be indicating correctly. It doesnt seem to be erratic or anything.

-I took the IDM apart this morning too. Inside looks fine. I did a mod to the IDM a while quite a while ago so I guess that could cause the IDM to fail prematurely but none the less, the inside of the IDM looks to be ok at this time. No evidence of water damage.



Anybody have any suggestions???
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Old 08-31-2008, 04:21 PM
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if you can locate the IDM for your vehicle at recking yard for cheap, buy and replace to see if that solves it. IDM is a Ford only item, the IH version will not work. IDM's thru the stealership is about $1100.
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Old 08-31-2008, 09:02 PM
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I almost forgot

Ive been running a mostly used motor oil for the past 3-4 months. Since I bought the truck 3 years ago I have been running straight Jet-A about 50% of the time.

That being said, it could also be the injectors. The funny thing is that it runs fine on motor oil but it misses and idles up and down on diesel. Its been about 3 months since I have driven it on diesel.

I did a little experiment by running the used motor oil tank dry and filling it with 10 gallons of diesel. It idles just the same. The experiment was to verify that the problem is not the diesel side fuel. BTW, the truck has two seperate fuel systems.

Anyway, I found the IDM for $250 rebuilt but I am hesitant to spend that much and not fix the problem. Somebody wanna loan me a known working unit to troubleshoot with? j/k

any other suggestions?
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Old 08-31-2008, 11:27 PM
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Some more information

With the fuel bowl harness connected securely to the IPR , the connector as an assembly can move quite a bit on the IPR. This is just me speaking outloud here but Im pretty sure that the loose IPR connector will cause the symptoms that my truck has. Right?

Also, I already mentioned it that when I disconnect the ICP, the idle comes up about 200rmp and will start to hunt up and down. Pretty much the same as with the ICP connected. From what I have read, if the truck still runs with the ICP disconnected than the ICP is probably ok?

The most confusing part of this problem is that it runs fine on motor oil. Is there some kind of learning process that the PCM has and it forgot how to run on diesel? When I changed the oil today I ran it on the old oil and it didnt hunt for the correct idle speed. It has always missed a little at whether on diesel, jet-a, motor oil or veggie.
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Old 09-01-2008, 10:49 AM
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tried some more tests this morning.

-disconnected each of the under the valve cover gasket connectors individually. This made it run like crap and it was still idling up and down.

-disconnected both connectors to the gas pedal while it was running. Nothing at all was noticed.

-tightened the sheetmetal nut on the IPR. No difference.

-It seems to start its oscillation right when the glow plugs turn off. I can tell that just before the glow plugs turn off it oscillates a little bit then starts with large up and down swings when the plugs turn off.
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Old 09-01-2008, 02:09 PM
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even more updates

-i just went out and cleaned the EBP sensor tube.

-ran the truck with the sensor tube disconnected and the sensor electrically disconnected. I re-connected the sensor with the truck running. All tests made no difference.

-I noted that the idle only starts fluctuating after the glow plugs turn off. It seems to happen this way no matter what throughout all of the tests that I have performed.
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