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Sundancin · 02-26-2012, 12:26 PM

Hi folks, first post here on the sight, but after searching the internet I'm hoping you Cat folks can steer me in the right direction. My Cat is not in a motorhome, but an "05" M2 Freightliner that avgs 2600 miles/week. I bought used w/183,000 miles. She runs pretty smooth, I am getting 9 mpg +/- .2th. My problem is intermittent and happens once or twice a month.

If I let up on the gas and coast down to a stop, engine will begin to run rough and will act like she is missing on acceleration. Will appear to have a lack of power, but still gets up to speed in the same amount of time, maybe slightly less. As I cruise, there is no indication there is a problem. When I stop again the problem is gone. The other scenerio is that as I coast down to a stop, if the problem is there, I can shut the engine off and restart and the problem is gone. Fuel filters are changed per recommended maintenance schedule, I buy my fuel from a high flow station and only form that station. I use the station for the DMax and VW TDI so I am ruling out fuel quality as the other two rigs show no signs of problems. I occasionally treat the fuel with Power Service.

I am an owner/operator with a limited budget so I do all my own maintenance. Information how to troubleshoot this thing seems limited and iRV2 appears to have the most insight on Cat engines. Can you folks help me out?

SVTotem · 02-26-2012, 05:58 PM

You are right Sundancin, there are several knowledgeable people on the forum and I am sure you will get some help here.

I am not an expert, but suggest you find a way to determine what codes your engine might be throwing during those events. A discussion with the CAT hotline might determine if you have a problem that a later ECU flash was meant to correct.

Sundancin · 02-27-2012, 04:11 AM

Thanks for the reply. Truck has an onboard diagnostic display in the dash and to date no codes have been detected. Did it again last night after a long coast down a hill to an exit off the interstate. My destination was 1.5 miles away, she missed and stumbled the whole 1.5 mile. Parked at loading dock and when I came out to leave she fires right up like nothing even happen and purrs all the way home without a hitch. Frustrating to say the least.

SVTotem · 02-27-2012, 07:00 AM

A call to Car hotline is your best bet. Give them the engine serial number and symptoms.

The C7 fuel injection system is driven by oil pressure. The heart of that system is the HEUI pump and they can have problems. That would be a high dollar problem, but this could also be as simple as a faulty sensor, so a call to the hotline should be your next step to get a more educated guess. 877-777-3126

Good luck, and when you get it sorted out come back and let us know what the solution was so we can help the next guy.

In the meantime keep checking back here. Someone with more experience than me is bound to speak up.

SVTotem · 02-27-2012, 06:08 PM

Another thought came to me. Could your exhaust brake be hanging up? Does your truck have a PacBrake with a butterfly valve in the exhaust? The need to be lubed in several places a couple times a year. If the butterfly sticks closed it could give you this trouble.

Try creating the symptoms with the exhaust brake off.

Sundancin · 02-28-2012, 04:15 AM

No exhaust brake, thanks for the #, will try that. Wish it would throw a code.

Sundancin · 03-03-2012, 10:15 AM

thanks for the replies so far. At the suggestion of a member here on irv2 (thanks SVTotem) I called the Cat Hotline with my engine serial #. Found the engine was lacking 13 computer updates. Found the complete history of the engine. I had it to Cat on Friday, they updated the computer and found the air inlet temp sensor was faulty and causing the engine to de-rate - making it feel like it was missing. The Heiu pump and injectors checked out good except for #2. Was dropping in and out once in a great while. Suggested an injector cleaner for a few tanks to see if it cleaned it up. Haven't tried it yet, but that is what I have found so far. I am relieved that it's not a pump problem. First run of week is Sunday night again and will report back.
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