Engine/Transmission (1998.5 - 2002) Lopey idle again

[NPloysa]

Well my truck's doing it again. It was fine for the last tank and a half and its back. If the handheld digital pyrometer I have at work can handle those temps, would I be able to test each cylinder and see one cylinder is running too hot? If the injector is not opening all the way, the cylinder should be running lean, which means hotter, right? Thanks



Nick

 

[RobertMiller1]

sensor?

it's not the cranshaft postion sensor acting up is it?

 

[NPloysa]

I am not sure if it is or not. Guess I need to check that. It only does it at idle, between idle (860 rpm and about 950 rpm) and is not noticeable above those speeds.



It cleared up for about a week and a half with some Mac's Diesel Additive from NAPA. It seemed like it went away as soon as I put a few miles on her with that in the tank.



I have a feeling its a lazy injector but I could be wrong. I will check the CPS.



Thanks



Nick

 

[RobertMiller1]

rough idle

I had a miss at idle. truck had been perfect smooth idle previously. after a couple of weeks, it went away. I now believe it was fuel.



get your next tank of fuel some where else. That is high volume diesel sales.





It may be winterized fuel, being used too late in warm weather.



or water in fuel

 

[Oil Burner]

Lean air/fuel mixture wouldn't create heat in a diesel, right? I thought that was a spark ignited gasoline engine rule. I could be wrong.

-Jason

 

[Hohn]

True-- leaner cylinder would run COOLER.

 

[NPloysa]

Yeah, I am going to probably top off my half-tank tonight just to get it mixed in better. This was the first time I got diesel at that place but not the first time it happened so IF it was the diesel, many places give my truck the problem.



And yes, a leaner cylinder will run cooler, DUH me!

 

[Harry V]

Ever come up with a specific cause? I experienced this yesterday for the first time. Just finished pulling my trialer back from the beach. Started it up after i unfooked and then it started. Gave it some gas and it seemsd to clear up. Lift pump pressures fine. Outside temps about 75 which is one of the first warm days. I haven't had any trouble with diesel fuel before... and I try to buy it at the same place.



I have 275hp injectors, PDR HX35, EZ, AFE filter and 4" exhaust. These all have about 3K on them.

 

[gonehuntingagain]

I had the lopey idle for a while. It started out intermittently at first, and seemed to go away if I only used fuel from a Chevron station. Then for several months it went away completely, regardless of what fuel I used. Next it was on - off - on again. Finally it started again in January of this year and would happen every time I started the truck when it was cold - it would go away when it was warmed up completely. I finally took it in to the dealer to have them look at it. They started it cold in the morning, so when they pulled it in to the shop it was loping. The mechanic tested the LP, which was fine (my guage reads 13 psi idle, 8 WOT). The mechanic plugged in the Cummins tester and found an intermittent fault in the injection pump - which they replaced under warranty. Mechanic said the one he pulled off was a remanufactured one, so it was replaced before I got the truck (with 59000 miles already on it and a weak lift pump).



Make life easier and find someone with the Cummins tester to check the injection pump.



Good Luck