My son's 2003 DHS had been running fine but after he filled-up the caddy and few miles down the road it began running sluggish, knocking...at WOT the RPMs run up but shifting is slow and it does not get down the road as you would expect with WOT.

Easing into the throttle the caddy drives and shifts fne and will operate at hwy speeds. We put some fuel cleaner in and are running the fuel out.

Any thoughts? Just bad fuel, sticking EGR valve? We haven't checked for thrown codes yet but plan to.

It sounds like he put diesel in it. Did the pump hose have a green handle?

:highfive: Diesel......best guess. Slug of water from low station tank.......maybe. Car.......probably not.

Well, the diesel nozzle should not fit but incase he did put some diesel...what would the outcome be. Simply run the fuel out or drain?

Doubt that is the case. If there was too much diesel it probably would not even run.

Yeah, it does not smoke just won't get up and go. RPMS run up where there supposed to be at WOT but the caddy is just moving like it should. Rolling at about 30 and going to WOT it downshifts and RPMS go up and it accelerates but not anything like it should.

Any more thougts?

Yeah, it does not smoke just won't get up and go. RPMS run up where there supposed to be at WOT but the caddy is just [U]not moving like it should. Rolling at about 30 and going to WOT it downshifts and RPMS go up and it accelerates but not anything like it should.

Any more thougts?

Trouble codes might provide a clue. Here is how to display trouble codes (DTCs):
http://www.cadillacforums.com/forums/cadillac-tech-tips/55172-how-pull-codes-got-codes-warning.html

Plugged CAT? Any DTC's?

Try the fuel filter. I change mine every 15k.

Good grief!

My sentiments exactly Jim.

:hmm: :confused: Something escapes me............

:hmm: :confused: Something escapes me............Read Post #10.

:cool: I did before I posted. :helpless:

(as an aside, I got antsy and replaced the fuel filter at 43,000 on my '02 in Sept. Cut old one open. Looked like I had put it in the day before. Dead nuts clean. Non-issue.)

DTC - B0429 - Temperature Control #3 Rear Circuit Range/Performance...and this means what?

DTC - B0429 - Temperature Control #3 Rear Circuit Range/Performance...and this means what?Not related to your engine performance symptoms.

DTC - B0429 - Temperature Control #3 Rear Circuit Range/Performance...and this means what?
It is for the auxiliary (rear) temperature actuator. Rather common. It means that the actuator is not in the commanded position. If you do not notice any problems with the rear seat temperature, ignore it.

It is for the auxiliary (rear) temperature actuator. Rather common. It means that the actuator is not in the commanded position. If you do not notice any problems with the rear seat temperature, ignore it.

Ranger, You first suggestion was right, clogged CAT. We R&R the CAT and the caddy runs great! Thanks for your help.