I hope you guys will be able to help me out because I'm at a complete loss.  So i have 2002 dodge 2500 with 174k and it has a rough idle when the motor is at operating temp.  The truck idles just fine when it is cold, only when it is hot does it start idling like s**t.  It almost sounds like it is missing, but I don't think it has a miss,  I don't know what else there is to replace on this thing, everything is all new.  This is a daily driven truck, it does not have a programmer on it, just 100HP injectors, 60/67/12 FPI turbo, 4in exhaust, BHAF, gauges.  Here is a list of everything that have been done to the truck in the last 3k miles and it has not solved the problem.  

New Vp44 about 1k miles ago

Air dog 100GPH about 500 miles ago

New MAP sensor

New IAT sensor 

New CPS

New injectors (100hp DDP)

New connector tubes

New batteries

All new battery cables( cleaned and checked all grounds)

New alternator

 

Please let me know if you have any ideas about what this could be, just need ideas about where to start next.... APPS? ECM? Dodge wiring? 

 

Thanks,

I have been wondering if doing the WT mod would solve my problems or just help prevent other issues.  Either way its a good idea. 

Yes hot wiring would remove the ECM from the running. The VP44 will only idle. If you had the black box it would have a high idle switch.

so if i hot wire the VP and it idles fine, then is it ECM or wiring or something else?  Where would be the first place to start?

Do the VP Hotwire test on warm engine at operating temp when you are experiencing the rough idle. I  would do the WT ground just because, it may or may not help your issue now but while your at it pull all your connections like the firewall plugs and big black and white plug in the PDC, look for any damaged or corroded pins, clean with contact cleaner, do not use dielectric greese.  
 

It does sound like your loosing communication somewhere being it clears up when you put it in gear,  If hot wire test clears up idle it may confirm ecm or electrical problem 

I will do a hot wire test this weekend.  I did notice today that the idle was off slightly while sitting at a stop light.. its not as bad as when in park, but it is noticeable. 

So, im putting a breakout box on the truck Tuesday. So, if it runs perfectly with the break out box on, what should I look at next ECM? I don't know what else it could be at that point...??  Alternatively, if it runs like **** it has to be either the vp or injectors.....correct or could it be something else??

Edited March 7, 20214 yr by Krlspokane12

Should I pull those ddp injectors and reset them? They are all (double checked) set at 290 bar, I know that's low but it what they called for them to be set at.  It might help a little bit, but I had the prior dap injectors set at 315 and it still ran like s**t but not nearly as bad 

290 is pretty low.  That and IIRC the DDP have a bit different spray pattern than Bosch. Combine the 2 and they could be the culprit. 

 

21 hours ago, Krlspokane12 said:

Should I pull those ddp injectors and reset them? They are all (double checked) set at 290 bar, I know that's low but it what they called for them to be set at.  It might help a little bit, but I had the prior dap injectors set at 315 and it still ran like s**t but not nearly as bad 

 

Stock minimum is 293 bar with the high end at 327 bar.

 

 

So it's not injectors now move to checking the VP44.

Edited March 8, 20214 yr by Mopar1973Man

Will do, maybe I got a junk reman vp???

It does happen.

Yup. In the years I've been buying DAP injection pumps and installing in customers rigs, I've only got ONE pump that was bad out of the box. It had a instant P1689 code and if you touched the throttle it jumped to 1,500 RPM and that's it. Normally all VP44 pump have to make the grade on a Bosch 815 test stand to get the new PSG programmed and flashed it. Takes roughly 3 hours on the Bosch 815 test stand per pump. Asked DAP for RMA to get the replacement and BAM! after being installed its was back to normal again.

 

This happened to me last summer a matter of fact I managed to punch the fan on the engine trying break loose the pump gear puller. So be careful too...

 

Bad VP44 pump and split my finger open (pretty bad), and to be starting the COVID-19 pandemic locally... 

 

 

 

 

Edited March 8, 20214 yr by Mopar1973Man

We will see tomorrow when i put the breakout box on it.  Hopefully its a bad pump and i can just get it warrantied.  I don't think that the injectors are the entire problem since it ran crappy with both the DAP's and DDP's.   would it be worth it to set the POP pressure higher on the DDP regardless of a pump issue? 

 

2 hours ago, Krlspokane12 said:

would it be worth it to set the POP pressure higher on the DDP regardless of a pump issue? 

I would think so, but I would not do it until you figure out the main problem. Change one thing at a time so you're not guessing. 

So, I put the break out box on today and it made no change to the way the truck runs.  Still idles like crap and threw a p1693 code.  So I'm guessing either a vp issue or something wrong with the injectors???

Like I said before the P1693 doesn't exist by itself. Injectors can run poorly when they are popped below 300 bar. Typically around 280 bar it get like a misfire and rough idle. Now in a bit of studying I've done on injectors you can lose up to 5 to 10 bar within the first 25k to 50k miles. As the parts settle and wear in the pop pressure always drops a bit.