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Engine Cutting Out

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I bought this truck a couple of weeks ago with the owner telling me that he thought it needed a new VP44. The one in it was rebuilt just over a year ago. I've been working on some of its other problems and trying to figure out if it is in fact the injection pump that is causing the trucks problems. Basically the truck will sometimes start missing and farting. Sometimes it is just a minor little blip and sometimes it is bad enough that it will die at idle. It happens at all RPM ranges but is definetly worse when there is no throttle applied. Some days it does this right off the bat and other you can drive for 30 miles without any problems. When I got the truck it had codes p1689, p1690, and p0121. I read Moparman's post about the fuel system relay causing p1689, changed it out and cleared codes. Now after about 12 hours of running since, only the p0121 code has come back. My understanding is that it has to do with the APPs sensor. This morning I took the scanguage II out of my dad's truck and drove 40 miles down the highway. I noticed that the LOD (engine load reading) was flucuating a bunch on a flat highway with cruise control engaged. It was usually around 30 but would sometimes bounce up to 48 or down to 16. This was true when the engine was running well as well as when it was running badly. Also seemed to bounce too much around town. I've checked for air in the fuel system, done several APPs resests, and done the PCM and ECM checks listed for code 1689. Does anyone have any idea what might be causing these symptoms? Can a bad APPs cause problems like dying at idle or is it only higher in the RPM range? Any idea what might be causing the screwy engine load reading? Do VP44s die without codes? The truck is stock except that it has a 12 valve exhaust manifold on it (something I will be fixing this week.) Any help would be greatly appriceated, I am ready to buy a VP44 but I don't want to throw a bunch of money at it only to find it was the wrong thing.


99 2500 NV4500 4x4 Stock for now

Last edited by Mattatat; Today at 01:14 PM.

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