Engine/Transmission (1998.5 - 2002) Engine stumbles/misses at idle. Why?

[Craig DeYoung]

Recently I've noticed that my engine will stumble or miss after I've been driving steady for a while and come to a stop. When the idle kicks down from 1000 to 850, I can feel the miss, random but persistent. The tach drops with each miss. If I bring the idle up to 1000 for a few seconds then let it go back to 850, it's usually OK. I have a manual trans. A few things I noticed that I'm not sure are related: I found aluminum(?) shavings in my fuel filter cannister two weeks ago while changing the fuel filter. I had to do the 20 second prime four times to purge the air (before I only had to do it once or twice). When I checked my fuel pressure between the lift pump and filter cannister, it was zero. Fuel does dribble out, though. Seems pretty obvious that I have a bad lift pump, and I'll be happy if I replace it and my idle problem goes away. I'll be ticked-off if my high pressure pump is ruined because it wasn't getting enough lubrication or cooling and it is somehow damaged, causing my idle problem. Can anyone think of another reason why I might be having the miss at idle?

Craig

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1998. 5 BE7L33 4x4, NV4500HD, 3. 54s, 255/85-16 Mud Rovers, Cummins uprate kit, VDO gauges

 

[Chad Sheets]

ECM reflash. Thats what others report as being the culprit. Never personaly had to deal with it, so not 100% sure. Better get a set of gages hooked up also.

The shavings are more likely from the canister itself I would guess. I have seen them and its the same material as the canister is made from.

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Always ready to help!
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[madams]

Check out Fritz's TSB page.

I had the stumble. There was a specific mfg run . . Some date in late Aug99, and if I remember a series of serial numbers.

I clearly fell in that range of reflash with my Y2k.

The only other stumble issue I remember on the board is there were a few of the bombers installing one of those fueling boxes where the problem showed up after the install . . and went away once disconnected.

The keyword is stumble . . look through the old posts.

As for my experience, there was no friggin way you could anticipate a stumble was comming on. It was as if the engine shut off for a second then back as nothing had happened. Never noticed whether the tach saw it.

Couldn't force or prevent it from occuring, seemed to stumble once per tankful . . and seemed I could only experience that condition at idle. The flash and the trailer hitch recall was performed at the same time . . and is the only time it was in the service isle. The Flash fixed my problem . . stumble never returned. Seems to be getting a little more fuel since the flash, I did notice a bit more smoke winding through the gears quickly . . but nothing I can hand my hat on.

Others have reported stumble under load . . but in all cases, including mine, is it never appeared as a "miss" and was a very random event.

Sounds like you have something else going on . . good luck. Keep us posted

Michael

 

[Bumble]

CD,
Maybe this is something you should bring up with your dealer before the warranty expires? Seems you only have a few more months left.

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2001, 3500, Cummins, SLT, 5sp, 3. 54LS, camper/tow package, 4x4, 165 watt backup lights, Thomas powered on-board air system, Grovers.

 

[Craig DeYoung]

I am going to install a new lift pump tomorrow, but I think I know what was causing the miss: bad fuel. The miss lasted for about a week, and was not present today. I refuelled last night at my regular fuel stop. My last tank (about a week ago) was from a station I had never been to before. I will confirm that it is gone, then replace my lift pump, since I know it is bad. Thanks for the advice!

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1998. 5 BE7L33 4x4, NV4500HD, 3. 54s, 255/85-16 Mud Rovers, Cummins uprate kit, VDO gauges

 

[madams]

Craig;
If it was fuel . . don't forget to run a fuel conditioner that has a dispersant in it to absorb any remaining water or bad stuff.

Then after you're confident you got all the bad stuff out . . change the fuel filter . . then do the lift pump.

Happy you have a handle on it . . Good luck
Michael

 

[TowPro]

That lift pump is covered under the 80K mile HD Diesel emissions warrante on our 98. 5's. I just got my first lift pump replaced, at 77K miles. Now I have 15psi at idle, 12psi at WOT. The part number on the pump ends in C (rev C is the latest pump)

Originally posted by Craig DeYoung:
I am going to install a new lift pump tomorrow, but I think I know what was causing the miss: bad fuel=

 

[Souders]

You refered to Fritz's TSB for this problem. I tried to find it and had no luck. Any help finding them appreciated.