Hi folks,


New to the forum, got a question. '94 k2500 6.5TD starts easy, pulls strong and smooth at all speeds. Crossed the Rocky Mountains like a champ a couple weeks ago. But just this week it started idling rough. It'll miss, kind of chug once, the whole engine will rock once in the truck, and RPMs will dip for just a fraction of a second. Then, just as soon as it happens, it's running fine again. It'll be good for 15-30 seconds, then it'll do it again. It'll start happening more frequently then, and it'll be once every 5 seconds or so. But there's still no problem off idle. Even if I hold her at just 900-1000 rpm, there is no detectable misfire.


I've replaced the OPS, lift pump and filter. Jumped power to the lift pump and flushed the fuel lines for a few seconds. Got a fresh tank of gas and a dash of Sea Foam in the tank. Seemed to run fine after fueling up, for about 5 minutes. Then it started happening again. Maybe temp related? Could this still be the PMD, even though it's fine under load? Also, I get the "high EGR Baro" code every once in a while. Related? I love my truck but this recent bad behavior is getting frustrating - please help.


-Digitalsasquatch

Can be PMD. I always say that with caution, because it's most over diagnosed problem. It causes no codes, but does just what are having. PMD's do have temperature problems, and the are prone to failure. Check also all conections on the IP, and engine ground, just to rule out any other electrical gremlins. Engine ground is the braided cable on passenger side head to fire wall. Edited by: knkreb

Corrosion/connection in the wiring harness is a best guess. PMD is the 6.5 boogie man.

Corrosion/connection in the wiring harness is a best guess. PMD is the 6.5 boogie man.


After being visited by the boogie man 3 times, it is not out of the realm of possibility.


But before condemning a PMD 1st, do all the troubleshooting 1st, wiring connections, fuel filter, lift pump delivery & power tests. Remote mount PMD though makes it very easy to TS a FSD/PMD,

Do you think maybe the EGR valve or control solenoid is hanging up and the rough idle is exhaust gas being dumped into the intake? Disable it and see if the code/condition still exists.

Good information, guys. Thanks.


Texas Diesel Guy - my egr code and the rough idle come independantly of each other. As a matter of fact, they've never happened at the same time, or even within 5 minutes of each other. Could there be some kind of delayed reaction? Another thought; could this be bad fuel? Symptoms seemed to lessen after I added a can of Seafoam.


-Digitalsasquatch

you have probably already checked this but just to be sure...the air conditioner will cycle if you have it on even with the fan off. so if your function selector is on defrost or the AC switch is depressed(not necessarily lit up) it will cause the compressor to cycle intermittently and this will load the engine at idle. might be worth looking at.