Starts, runs smooth for a minute, then lopes/misses, and dies. - Ford Powerstroke Diesel Forum
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Old 08-29-2011, 11:18 AM
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Starts, runs smooth for a minute, then lopes/misses, and dies.

Hey guys,

My 96 7.3PSD has stumped me for a while now. It starts okay, idles smooth as a baby's bottom for a minute or two, then lopes badly for 15-30 sec and shuts right down. Will not restart unless I let it sit for a while, sometimes a few minutes is enough, but it just repeats the same symptoms.

It doesn't set a CEL. Ive watched fuel pressure at the schrader valve and it doesn't drop off. Bounces around 55-65 the entire time. Doesn't leak down after it dies either. HPOP res stays full. Fuel bowl stays full. I thought maybe it was the IDM, I pulled it apart and it did have some moisture in it. I cleaned it well with contact cleaner. I'm not sure I think it the IDM anymore with how repeatable the issue is and the fact it runs fine at first. Maybe the HPOP isn't pumping after it warms up? But you wouldn't think it would act like this... Truck has 340,000 and AFAIK its never had injectors or HPOP done. Just glowplugs/relay and a turbo and a few clutches and some pulleys. I swapped out the CPS just in case, but no effect.

EDIT: I did remove my pot from the ICP circuit to take it out of the equation. Is there any chance I could have hurt something in the PCM by having it in there? I believe it is a 0-10k pot, I did add a resistor inline so I could never go below a certain resistance, maybe 2 or 5k? Don't recall.

Any ideas without access to a scantool? Can I monitor hpop press using the icp sensor and a voltmeter/ohmmeter?

Last edited by Boss.Hoss; 08-29-2011 at 11:21 AM.
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Old 09-08-2011, 01:02 PM
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No lovin' for the Hoss man?

I did end up reading of a similar issue that was resolved by cleaning up the battery connections... I did that it deffinately helped... I was able to drive the fuel station and back without issues, the next day it idled in my yard for about 20 minutes then loped for 2 minutes and shut down again... must be more electrical gremlins somewhere... I thought it was fixed... False alarm..

Any other ideas guys?
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Old 09-08-2011, 02:24 PM
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hows the oil level look
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Old 09-08-2011, 02:30 PM
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Oil pan is full. This truck never uses or leaks any oil, even after 340K+ miles! The HPOP resivioir also stays full. I think its electrical. If it starts loping I can turn the key off and back on while I'm going down the road with it in gear, and the misfire will go away for another couple minutes.
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Old 09-08-2011, 02:43 PM
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Have you changed the CPS ?
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Old 09-08-2011, 02:56 PM
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Quote:
Originally Posted by Chop View Post
Have you changed the CPS ?
Yes, as mentioned in the OP, I chainged the cps though I was still getting tach signal with the old one. No effect.
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Old 09-20-2011, 01:58 PM
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Well, finally found a used IDM for $50 online and tossed her in... all is well. guess this goes to show, GO WITH YOUR INSTINCTS! That was the first thing i suspected and i did find moisture in it, just didn't want to drop the coin for a new one!
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Old 09-20-2011, 02:21 PM
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Congratulations on your gremlin elimination,your first thoughts seem too always be the answer don't they?
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Old 10-08-2011, 03:44 PM
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These IDM's go out that easy?
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Old 10-09-2011, 03:42 PM
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Quote:
Originally Posted by Spud Monkey View Post
These IDM's go out that easy?
Yup, they are prone to getting water in them due to their placement on the inner fender right beneath the hood-fende seam. I pressure washed my truck (the exterior, NOT under the hood) and I apparently got water inside which smoked the high voltage circuitry inside. These things produce 100VDC, so any kind of moisture that makes it in can be very easy to break things...
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