Engine/Transmission (1998.5 - 2002) "miss" at idle

[AKEggy]

My lift pump started leaking externally about 3 weeks ago. I parked it the first day I noticed it and installed the in-tank kit from Chrysler. About a week after that, the engine quit while driving down the road. I pulled code 1688 (I think), anyway, the code for internal pump failure, no further diagnosis needed. Replaced VP-44 with a rebuild from Bosch. Ran fine the first night, but the next day coming home from work, it developed a miss at idle after it was warm. Just enough to shake the truck a little. The longer it idles, the better it gets.



I checked fuel pressure at the filter after I installed the pump and have 9-10 psi at idle and 5. 5-6 psi at full load full throttle. The guy at the shop where I bought my pump said those were good numbers for the in-tank pump.



I haven't bled the lines since the initial start up and plan to do so tomorrow, but I'm afraid it may be a bad pump. Any other ideas. I did a search and found a few threads, but none of them had a resolution posted, only ideas.



The truck is a 1999 with a little over 118K miles.



Thanks for any help you can offer. I've been lurking since forever and have been really impressed with the knowledge here. Thought I had better pony up my membership money because of all I've learned here!!

 

[GDMRTN]

Those are really good numbers for the intank unit. Fill out the signature so we know what we're dealing with. You mite have a piece of junk stuck in an injector from the failure. Just a thought.

 

[obert]

I had a new VP installed under warranty in '01. I've (well, my truck has) had the symptom ever since a short time after that. Some say "that's just the way it is", but I dont really buy that.



For me, the miss is only in idle sequence, the slightest touch of throttle smooths it out, or a slight load such as deadheading hydraulic pump with steering or brakes, even the a/c compressor kicking on is enough to clean it up.



I, too, lean toward injector issues for a number of long winded reasons. One of these days I'll get off the cash for some new sticks.

 

[AKEggy]

Yuck...

Went back to the place I bought the pump and he had never run across this problem before. He rebuilds as well as installs his rebuilds or Bosch's pumps. He would be happy to send itback to Bosch for them to bench it, but I'll be out a truck for awhile while all the shipping and testing takes place. He suggested going to the Dodge dealer and see what they thought.



From talking to the Cummins tech. at the Dodge dealership, he's seen it before and suspects a defective pump. I'm going back tomorrow to drive him around with his DRB hooked up to hopefully capture some data I can send in with the pump. I'm concerned that it won't act up on the test bench at Bosch because it only acts up hot on the truck. Don't really want to go through the install process twice, wait for a week or more with no truck, and get the "nothing wrong" story from Bosch. It's liveable the way it is and apparently doesn't affect performance, but for durn near $1,500, I want my truck running as smooth as it did before my original pump went south.



I checked for codes again tonight, and there's still nothing there. The lift pump harness is in tact, and no fuel leaks anywhere. Guess I'll see what the Dodge guy has to say tomorrow.



Thanks for your input, any more would also be appreciated if you've experienced this before.

 

[Bloomy]

I had a new VP installed under warranty in '01. I've (well, my truck has) had the symptom ever since a short time after that. Some say "that's just the way it is", but I dont really buy that.



For me, the miss is only in idle sequence, the slightest touch of throttle smooths it out, or a slight load such as deadheading hydraulic pump with steering or brakes, even the a/c compressor kicking on is enough to clean it up.



I, too, lean toward injector issues for a number of long winded reasons. One of these days I'll get off the cash for some new sticks.

Brother-in-laws 98 has the exact same thing. If you touch the brakes or anything it smooths out. The VP is on its way out on the truck anyway, so that could be it. I don't know though. Haven't been able to figure anything else out.



Thomas

 

[JesseJ]

My truck had a miss at idle with stock sticks but it didn't show up until after VP44 replacement. It wouldn't do it all the time or very often so I didn't worry about it. Like the other guy said, anything off idle made it disappear. Don't know what it is. It will rarely, occasionally do it now but I figure that's the bigger sticks and altered timing. It could be some small air pockets that need to get worked out any time you open the fuel system like that. After I put in injectors, it missed bad for a couple of days of driving before it finally worked all the air out and got smoother. Just an opinion, ditch the in-tank pump, nothing but trouble.

 

[rweis]

Just an idea, clean your IAT sensor. At least check the resistance when it is hot and causing the problem and then compare the values you get to what it should be.



There is an interesting thread about some guys adding a parallel resistor to the IAT because they had a injection miss problem. Some trucks seem to have the problem, some don't.



I am reasonably sure you will get a 0216 if the advance piston in the VP44 is not able to move quickly and accurately.



Another idea is thee is very little cooling fuel flow through the VP44 at idle. Maybe more flow at a critical temperature might just be enough to keep the PSG from malfunctioning. I have a fairly involved thread about cooling the VP44 and cooling the fuel.



I would try cleaning the IAT first.



Just a thought,



Bob Weis

 

[AKEggy]

Well... finally got it sorted out. I had to send the pump back to Bosch, they wouldn't just exchange it for me. Bosch called the place I bought the pump from and they told him that when they rbuilt the pump, the guy dropped a screw for the speed sensor. He installed a new screw but didn't bother retreiving the one he dropped. It destroyed the rotor assembly. They were surprised it was running at all.



Anyway, they rebuilt the pump I sent in, and I installed it earlier this week. All seems OK so far.



It's a bummer having to wait for shipping time both ways as well as diagnosis and repair time when it's your only vehicle

 

[Ncostello]

Glad he's not a surgeon doing open heart or something like that. Whats wrong with people? I guess I shouldn't even have to ask.