APPS issue, i'm stumped

[benn]

Hello all!

Ongoing issue with APPS. Truck developed heavy miss between 12 and 1600rpm wether truck is cold or at operating temp. No codes in computer, no CEL. Tested voltage of factory APPS (after trying resetting it) .54-.79, dropped to .51-.59, jumped to 1.02-1.73, dropped 1.51-1.57, jumped 2-2.7 etc. eratic voltage all the way to WOT at 3.81. ok, bad APPS. New timbo APPS installed per instruction, reset everything, started and miss is gone. smooth voltage .68-3.79. drove 1.5 miles and parked for three days. started back up, truck missed and loaped for ten seconds at idle (never happened before). idle cleared up, but same miss is back between 12 and 1600rpm. No CEL, no codes. Tested voltage of new APPS, same as before, dropping and jumping at same volts. Any ideas on what to check next? Thanks!

oh, its got 116,000 miles. The VP was changed at 54,000.

[dorkweed]

Do you have the "miss" with a cold engine, or after she gets to operating temperature, or both???

[benn]

Both, misses cold and at operating temp.

[dorkweed]

and parked for three days. started back up, truck missed and loaped for ten seconds at idle (never happened before). idle cleared up, but same miss is back between 12 and 1600rpm.

Is this a "daily" driver truck…………….or do you let her sit for days at a time???

There will be others here shortly that are more versed in 2nd gens than I am to help!!

[benn]

yes, its my daily driver. doesn't sit for long very often.

[mariner]

If you contact Timbo, I hope you had better luck than I did. I Emailed regarding testing the new Timbo I installed and heard nothing back. I too had some problems but they cleared up fortunately - possibly connection not fully contacting. Anyway, no more problems with my Timbo APPS just yet.

[Dieselfuture]

Hello all!

Ongoing issue with APPS. Truck developed heavy miss between 12 and 1600rpm wether truck is cold or at operating temp. No codes in computer, no CEL. Tested voltage of factory APPS (after trying resetting it) .54-.79, dropped to .51-.59, jumped to 1.02-1.73, dropped 1.51-1.57, jumped 2-2.7 etc. eratic voltage all the way to WOT at 3.81. ok, bad APPS. New timbo APPS installed per instruction, reset everything, started and miss is gone. smooth voltage .68-3.79. drove 1.5 miles and parked for three days. started back up, truck missed and loaped for ten seconds at idle (never happened before). idle cleared up, but same miss is back between 12 and 1600rpm. No CEL, no codes. Tested voltage of new APPS, same as before, dropping and jumping at same volts. Any ideas on what to check next? Thanks!

oh, its got 116,000 miles. The VP was changed at 54,000.

I would love to help you but I got same problem only at higher rpms, put timbo apps got a bit better but problem is still there. No codes, but mine misses more with a load on, or its more noticeable. Get some literature from blue chip diesel on how to trouble shoot vp, it sounds like computer on top of vp can go bad without setting codes. That's what I think is going on with mine. Been tracing my problem for over two years now. Good luck:cheers:

[dorkweed]

Have y'all "pop-tested" your injectors???

[Dieselfuture]

Have y'all "pop-tested" your injectors???

No that would make since , I got all orings and copper washers to pull my injectors and adjust valves as soon as I check my apps and map sensor voltages, driving with voltmeter on correct wires. If it all checks out then that would be my next step.

[benn]

issue started with my stock injectors around 110,000. i had a new set of bosch RV275's on the shelf so i put them in. no change.

[Dieselfuture]

issue started with my stock injectors around 110,000. i had a new set of bosch RV275's on the shelf so i put them in. no change.

Read this it made me think:think: http://m.bluechipdiesel.com/site/vp44_diagnostics.html?imz_s=jrqvotplrc17p03n98eejir1g4

[benn]

Everything is pointing to the VP's brains. Went ahead and got a VP from DAP ordered up, will update when installed. Thanks again for all the thoughts!

[Mopar1973Man]

If anyone is going to point at a VP44 there is 2 causes for the PSG to fail. 1. Fuel pressure being too low and allowing the PSG to overheat and cause damage to itself. 2. Too high of AC noise levels and the AC power doing damage to the electronics of the VP44. #2 happens to be the most dismissed answer by "I just just bought a NEW alternator not a re manufactured." This still doesn't mean anything I've seen new alternators now (Bosch and ND's) both fail out of the box brand new. Still I highly suggest that you check for AC noise either with a DVM ant the battery terminal of the alternator or use a O-scope like here.

[Dieselfuture]

Everything is pointing to the VP's brains. Went ahead and got a VP from DAP ordered up, will update when installed. Thanks again for all the thoughts!

Don't mind me asking, which one did you get? looks like there are a few to chose from. Also I heard that you can ran SO instead HO for more power, not sure how to make it work, if you need a new ecm or just bigger injectors, just a thought, I now you already ordered it but I'm thinking out loud, if I end up getting one how hard is it to put SO pump for more power for same amount of money. Anyone?

[diesel4life]

There are no benefits of running an SO pump unless you are over the 500-600 HP mark, and then a Hot rod VP would be the way to go. Of course, you would have to have the injectors, injector lines, and lift pump capabilities to keep up with fueling demands.