Cummins 605/2050 immediate RPM drop issue

[WICT800]

4:10 rears with Low Pro 24.5’s just makes shifting a nuisance when the motor is trying to recover after the air throttle slams shut between each shift. Also when on job sites where low speed drivability is crucial it’s just a pain in the ass

[tree98]

What makes you think the cause is the air throttle closing and not something else?

[WICT800]

(10-21-2021 )tree98 Wrote:  What makes you think the cause is the air throttle closing and not something else?

That’s what I’ve been trying to figure out, what is causing that air throttle to rapidly change position, from my understanding it sees signal from the EGR but with no check engine light I have received little help from the Cummins dealer. I’ve also made a mention that the truck turbo flutters out of the breathers on shut down which seems odd to me but the mechanic said “it’s programmed that way”. Believe me it’s been very frustrating, I have several videos of several trucks and none of behave this way.

[tree98]

I don't think your problem is programming related. Have you taken the air cleaner out and inspected the piping looking for restriction of some kind? What's the max it's boosting? Maybe take the tube off of the crankcase breather box (not sure of the actual name) maybe there's something in there restricting flow? Just seems like a flow restriction somewhere.

[WICT800]

(10-21-2021 )tree98 Wrote:  I don't think your problem is programming related. Have you taken the air cleaner out and inspected the piping looking for restriction of some kind? What's the max it's boosting? Maybe take the tube off of the crankcase breather box (not sure of the actual name) maybe there's something in there restricting flow? Just seems like a flow restriction somewhere.

Boost is about 30 psi, everything seems to be ok as far as intake restrictions, in top gear the motor does pull nice and smooth as far as i can tell, the lack of check engine light is strange if it was in fact a mechanical issue and not a programming issue, the truck has only 19,000 miles on it and it’s done it since brand new. When I first got the truck the bad Cummins Smart Acceleration enabled and that caused some issues as well.

[tree98]

Alright well I'm outta guess's. Let us know what you find out.

[WICT800]

Roger that, hopefully tomorrow I will get some positive feedback.

[schISM]

I had the exact same issue with a 22’ Peterbilt I purchased earlier this year. It was as if the VGT stage of the engine brake was active at all times except during actual engine braking. It would do this until the oil temperature reached 210f. Shifting around town was just ridiculous and you’d have to precisely meter the throttle if you hoped to get a smooth shift. I started at the dealer level with no luck and escalated the matter to a factory Cummins shop by way of Cummins Care. No luck at all. In the end I sold it and picked up a 2250. I’m enjoying the drive again.

[tree98]

How do you sell something like that? Didn't the guy test drive it?