Intermittent Bogging And Chugging

mchan68 · April 12, 2010

Hey GENTS. I have one here, a late-build 2004 that I replaced a long block about two years ago at 138,000 kms. under warranty for a catastrophic oil into coolant contamination. Vehicle is now back at 173,000 kms. complaining of intermittent bogging down during acceleration. Got codes P0299, P0407, P0488, P0603 and P1334 in CM, both on KOEO and KOER. Passes IDS EGR test. Only out-of-spec PID noticed was a slightly higher EBP reading at KOEO, but still within acceptable range. I know there's a TSB for a reflash to address P0407 and P0488 (for which one is available for this particular truck). Carried out pinpoint test AX, and all seems to point to replacing the EGR throttle plate assembly. I did notice that at KOEO, the throttle plate does seem to randomly sweep between FULL open and FULL close uncommanded. This makes sense that the truck would bog down if the throttle plate were to close uncommanded, setting DTC P0299. While monitoring PIDs, I did notice that EBP and MAP/MGP go wonkers when it bogs down as the engine revs up. Just curious if anyone else has ever run into this, or had to replace an EGR throttle plate for this concern before? Only reason for asking, is because it's now retail.

Aaron · April 12, 2010

Unplug the TP and go for a ride?

Mbl35 · April 13, 2010

had to do to unplug the throttlebody on a few units here, but thats becuase they barely would reach 40mph, unplug and good as new. Rnr throttlebodies fixed concerns.

cbriggs · April 13, 2010

Yep i have seen exactly that Mike, except mine had an egr cooler block off plate in it. The egr tp plate would hunt and try to create egr flow, but the position sensor was bad. The one i worked on would smoke, cough and backfire. (yes, backfire... i wouldnt beleive the customer.... until i "verified the symptom") The reason i finally figured it out was, during the concern mgp was pinned at 0. The bastard was pulling vacuum. Im assuming that with an open egr system the vacuum created would just pull massive amounts of egr gasses and choke the engine, without the backfire, smoke and coughing.

mchan68 · April 13, 2010

Yep i have seen exactly that Mike, except mine had an egr cooler block off plate in it. The egr tp plate would hunt and try to create egr flow, but the position sensor was bad. The one i worked on would smoke, cough and backfire. (yes, backfire... i wouldnt beleive the customer.... until i "verified the symptom") The reason i finally figured it out was, during the concern mgp was pinned at 0. The bastard was pulling vacuum. Im assuming that with an open egr system the vacuum created would just pull massive amounts of egr gasses and choke the engine, without the backfire, smoke and coughing.

That is EXACTLY what this truck is doing. Thanks Chris. And boy what a smoke show this thing sure puts out when it's doing it's thing.

cbriggs · April 13, 2010

Quote:

And boy what a smoke show this thing sure puts out when it's doing it's thing.

No doubt hey, i thought it was just cuz the egr was blocked off, maybe not. Apparently diesels arent meant to make vacuum.

On a side note, since the egr was dissabled anyways on mine, i removed the throttle plate from the shaft, and left everything else intact. P0488 is a non mil code. Customer was happy.