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znt1186 · 02-11-2019, 07:26 AM

Just took the coach out for a drive for exercise. Fired up and ran well until I tried the engine brake. Then I got a check engine light. Had a loss of power and some severe stutter in the engine. The check engine light went off briefly and came back on a few times. Stopped at a truck stop and the check engine light went away. Started back home and had low power coming up the ramp to merge. Showed about 32 psi of boost. After a bit, the power came up and the engine ran fine the rest of the way home. It did not seem that the engine brake was functioning properly, but the engine developed a lot of horsepower and ran fine. Anyone have any opinions on what might be going on with my engine? It is a Cummins 400 ISL.

Rsb3 · 02-11-2019, 07:40 AM

Just my thought with no other info, because I had similar symptoms 2years ago. Especially the low power plus check engine, ended up being the EGR valve.

Quincy · 02-11-2019, 10:55 AM

The check engine light is an emissions issue, the erratic performance could indicate a loose part, such as an O2 Sensor. Or, as mentioned above, the EGR valve.
Might be a good place to start.

Quincy · 02-11-2019, 10:58 AM

By the way, "exercising" the coach, weather gas or diesel is not necessary and can cause more problems than it solves. Especially if you are not going out for at least thirty minutes of "on the road" driving.

znt1186 · 02-11-2019, 11:08 AM

Actually, I needed to start the coach to relocate it at my home and did not want to just start for a few minutes and shut down. Had it on the road for about 30 minutes and got temps up to normal operating range. Planned a longer trip until the CEL came on. Normally, Elvira sits until ready to be used.

IndyHntr · 06-18-2019, 06:58 PM

Having same issue, thanks for all the info on this thread and I found another with info. Check Engine light always comes on when Engine Brake engages. I am guessing fluid surges forward and trips sensor. So will check all fluids. The fuel filter is brand new, first trip. So counting that out. Will let you know if I find anything.

znt1186 · 06-20-2019, 06:35 AM

Had mine checked out and it was a code for low fuel pressure. Repair shop was not able to duplicate the code again. They changed the fuel filters and the ones they removed were clean.They talked with Cummins could not reach a solution. They drove it about 50 miles running hard up grades and down and could not get it to happen again. Since then, we have clocked about 1600 miles with no problems. Still don't know what happened. It will probably come back around to bite someday.

znt1186 · 11-18-2019, 09:55 AM

Well, CEL is back. Last two short trips, CEL would come on a few minutes go out, come back on, go out for about 30 minutes or so, then it would go out and stay off until we got where we were going. Looks like it is back to the shop time.

nathaniel · 11-18-2019, 11:09 AM

Have you checked your antifreeze holding tank. There is little room for error on the low level sensor and it will put you in limp mode thinking your low on antifreeze regardless of water temperature.

znt1186 · 11-18-2019, 11:19 AM

Yes, the bubble is right where it should be in the site glass. No limp mode, just a CEL and a mild power loss. Seems to be a low fuel pressure code based on the shop check back in February. They talked with Cummins and no one could get it to happen again or determine a cause.

Caliber · 11-18-2019, 03:59 PM

Next time it happens, loosen up the fuel cap and listen for a Vacuum. Than try running it with the cap loose, it sounds like the vent to the fuel tank could be partially plugged.