Engine/Transmission (1998.5 - 2002) Idle loping very badly after startup?

[SLightfoot]

Hi folks;



Went to pull my truck into the garage this morning to rotate the tires, and after waiting for the "wait to start" light to go out, I started it.



It started up right away, but had a VERY lopey idle - almost as if you were pressing the accelerator pedal every 3/4 of a second. Not minor by any means. The tach showed the increase - perhaps going up 200 RPM or so repetitively - going rump-rump-rump-rump-rump. It rocked the truck back and forth even. I noticed that it set the "Check Engine" light also.



I pressed the accelerator, ran the RPM up to 2000 and it ran smooth, but as soon as I let it go back to idle, it loped really badly.



So then I remember back to a time once before where I was checking the lift pump flow by bumping the starter and opening the water drain on the fuel filter canister. When I restarted the truck after this, it did EXACTLY the same thing. It seemed the only thing that fixed this at the time was to bump the starter and cycle the lift pump a few times. I had guessed I got air in the system. At that time, it never set the Check Engine light though.



So, thinking back to that problem, I did the same thing this time - bumped the starter to get the LP to run for 20 seconds or so, then restarted it. Sure enough, this cured it again.



Unfortunately, I don't have a fuel pressure guage installed yet - although I am ordering one tomorrow.



What the heck is going on here??



This is starting to worry me, especially since just a month and a half ago, the truck for the first (and only) time totally died driving down the highway at highway speed. Never found out what caused that either... . maybe the two are related?



I'm really worried now, since in less than 2 weeks, we're hooking up the 5th Wheel and heading through the mountains on vacation.



Appreciate any insight guys,





Shawn

 

[Graphic man]

did you check for codes?

 

[SLightfoot]

No, not yet.



On my '99 you can't do the key-cycle thing to pull them - you need a code reader, which around my area is only at the dealer at $96 per shot.

 

[Kissfan113]

it is my guess but i would venture to say it is your injection pump goin kaput... . hopefully is it a simple fix

Kevin

 

[rivercat]

you could always go to your local borderjumper haven= autozone where they pull codes for free just BE SURE and disregard any advise or diagnosis they offer and write down the code #s to research yourself. As a former State Emissions Inspector I have had the expirience of sending losts of folks (to avoid the hassle of pulling codes for free) to the Zone and having them comeback with O2 sensors they don't need and no code #s. Seems Bosch gives em a bonus to fix every Check Engine Light by selling O2 sensors or something.

 

[gonehuntingagain]

My truck developed the "lopey idle" that you are talking about. It would go away after the truck warmed up or once the throttle was pushed. All of a sudden it stopped doing the lopey idle and was back to normal. The lopey idle came back a year later and would not go away - and started to get worse. I took it to the dealer (still barely under warranty). The tech checked the fuel flow (which was good) then put plugged the Cummins tester into the pump - this bypassed everything else on the engine and it still did the lopey idle. Dodge paid for a new VP-44 and all is well. The tech wrote it up as an "Intermittent fault at the injector pump" since no codes were ever set.