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FIX-IT, Technician
Category: Heavy Equipment
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DD15 Rough/Poor Fuel Economy

Resolved Question:

I am experiencing poor fuel economy and the engine idles and runs rough. I think the problem has something to do with the intake throttle valve and fuel doser and/or DOC inlet temperature.

The other day I had an event (active faults) that resulted in a complete turnaround. After the event, the engine ran smooth and got excellent fuel economy. However, it has slowly begun a regression back to where it was previously.

I will pay a lot more than $28 to get this problem resolved but it will take a little time and you must have access to Detroit...
Submitted: 6 years ago.
Category: Heavy Equipment
Expert:  FIX-IT replied 6 years ago.
Hello and welcome to just answer.i can help you with you records of the codes that we're active ? what has been replaced? ill need the last 6 of your vin to please..
Customer: replied 6 years ago.
HIGH 128 235 00
ENG SA00 SPN001037

We finished a 2000 mile run and were in our 5th day sitting. It is unusual for us to sit for 5 days in a row. We high idle (900 rpm) for 1.5 hours in the morning and then again in the evening (solar panels power the day). It was during the morning of the 5th day that the smoke and fumes billowed from the exhaust. I shut it down after only an hour with no faults and no regen indicators. I turned the key on that evening and while waiting for the instrument sweep to complete the faults appeared. I started the engine and noticed the level 2 regen light (flashing DPF indicator). I performed the parked regen and it took only 4-5 minutes to complete and I was expecting 15-20 minutes.

After the regen completed, I changed the idle to high idle (900 rpm) and after another 4-5 minutes the engine switched from running rough/loud to smooth and quiet - like a sewing machine. It has been this way ever since. I don't expect it to stay this way because it has done this before. After the recall on the fuel system it ran great for awhile. After the replacement of the metering valve? it ran great for awhile. It seems like every time the system is worked on it runs fine for awhile.

This leads me to believe there is something that gets reset to zero or default values when diagnostic equipment is attached or the fuel system is relieved of pressure? are there values that accumulate over time on the DOC inlet temperature that may cause things to drift and cause the intake throttle valve to close when it isn't supposed to? I only ask this because I can hear it close to perform a regen while going down the road. I confirm this by stopping and looking for the HEST indicator. Other times when performance is poor I can hear the valve close but when I stop no HEST indicator. Also, there has been a significant increase in soot in the oil samples.

VIN: AN6883

... tim
Expert:  FIX-IT replied 6 years ago.

ok,sorry to hear you having a a lot of problems,

click here.

there is one other recall that falls under your serial number that needs to be done,these sensors affect fuel mapping and can cause performance issues.

your code 1037 means high absorption rate to the aftertreatment which is a result of high idle time,there is a feature called auto elevate that fixes this that causes the engine to ramp up to a higher rpm to burn off all the soot in your after treatment,have you heard of this ?? any who,get the recall done if not done already,and keep me in the loop.

Customer: replied 6 years ago.
Why didn't the level 1 regen indicator light up when it was idling in the morning? the engine was running rough and smoke billowing from the exhaust but no indicator lights or fault codes until the startup that evening.

According to the regen strategy, at 900 rpm it should be 44 (25+19) hours before a parked regen is necessary yet I had only idled a total of 12 hours when the smoke came and the fault codes followed.

Why has the engine run perfectly for days following the hard event (fault codes and regen)? Did something reset at that time? if so what?

I will follow up with 10M7 and let you know...
Customer: replied 6 years ago.
Also, we tried the auto-elevate function but it conflicted with the optimized idle function so we turned it off. I would think they would work well together. And, this is worth a great deal to me so if we fix this you will get your bonus...
Expert:  FIX-IT replied 6 years ago.
do me a favor and look at your stack,is it clean? or is it black?
Customer: replied 6 years ago.
I ran my finger inside (weed burner) and it was dirty but not black. But doesn't the DPF trap the soot?
Expert:  FIX-IT replied 6 years ago.

yes it does,i wanted to make sure it was ok..

get the recall done and let me know how you do,

also to answer your question about something re-setting,that doesn't happen this thing should run like a top with little were saying the truck blows smoke sometimes,what color?


Customer: replied 6 years ago.
I will but it may be after Christmas. The only time it has blown smoke was the event describe above. It was dark, maybe gray, not black and not white...
Expert:  FIX-IT replied 6 years ago.
ok.merry christmas..
Customer: replied 6 years ago.
Thank you! and merry Christmas to you...
Expert:  FIX-IT replied 6 years ago.
Customer: replied 6 years ago.
The truck is being worked on with the modification you suggested as one of the tasks. In another forum is was suggested that I get the serial numbers off all the SAM and CAB modules and check then for recalls. They also suggest that I check the current versions to make sure they were all compatible. If I get this information can I pay you to look it up?

In an earlier post I stated that I thought something must have reset? Well I was looking through some documentation and found an instance where a reset is necessary but CSC must do it. Check out line 24 in the following document.
Expert:  FIX-IT replied 6 years ago.

alright i had a look at your truck has had 2 recalls on the ftl side and they were done,one was for water leaks the other for a software update for your sam modules.The software update that you sent me was for a old recall and it was either completed on you engine or not required.


Customer: replied 6 years ago.
You are correct. The reason that I wanted you to look at the document was that line 24 requires the technician to call CSC and ask them to reset the fuel map. What does this mean to you? aren't they reseting the values back to defaults?
Expert:  FIX-IT replied 6 years ago.
all that reseting means is updating the software,i don't know why they say reset but they are actually putting in updated software or mapping..
Customer: replied 6 years ago.
That makes sense (I suppose)...

I am still looking for a reason for the yet unexplained change in behavior. I like the new behavior but I fear it will not last. There have been several other occasions where a change to the fuel system has resulted in a short term performance gain.

We installed the 10M7 modification today. One sensor was clean and the other had quite a bit of soot. It runs and idles pretty smooth but we don't have the time/miles to see if the fuel economy is improved.

This is my first time with getting answers online. Are we ready to close this or should we hold it open to see how the fuel economy changes. I appreciate your help...

... tim
Expert:  FIX-IT replied 6 years ago.

go ahead and close and stop by sometime..

Customer: replied 6 years ago.
Where are you located?
Expert:  FIX-IT replied 6 years ago.
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