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2003 Duramax -
I have just recently replaced the motor in my 2003 chev duramax with a 2002 lb7. It got brand new Bosch injectors along with head studs put in it back in December 2013 when the engine went in. The truck has EFI live tuning from Nick at duramaxtuner.com in Illinois . After driving the truck about 600kms after all this was done it started to knock on higher rpms but go away with low rpms with No smoke. Took the truck to Smoke Em' Diesel Performance in Sask. to get the injector rates tested as they did the work. All checked out good for the new injectors balance rates, BUT the timing did show it was running 38* when it was tuned with the EFI to be 27*. After coming to the conclusion it was the tuning off, they sent the ECM down to duramaxtuner and after they had a look at the ECM it is saying that its giving the proper tunes and degrees in timing as was loaded on before. Bob said he's never really come across this and same with the guys at smokem diesel. Truck has run with the original 03 engine for 2 years with this tune and now acting up within 600kms of a different 02 engine. Has anyone heard of this happening before like timing changes as you drive? Its got all us stumped here not knowing what to look at next why this would happen. Any and all help is needed and appreciated!
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You need to provide more complete information on timing rpm and load...you should have the truck logged and compare the log against the tune. If you have an ECM issue, that may help illuminate it.
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Im not super mechanicly inclinded when it comes to diesels(gas is a different story) but Iv just heard back from Smoke Em Diesel and they said they heard from DuramaxTuner, everything in the ECM and flash file was perfect. Max timing is still set at 27 degrees. They did an erase and reload just incase it helps any, and as of yesterday the ECM is on its way back to us to put back into your truck to see if it helps any.
Before the truck left after the motor replacement we spent about 3 hours driving it around to verify proper operation and to record all the injector, fuel pump, timing, and temperature valves (as we do with all motor jobs) and they were all perfect where they should be. Once the ECM gets back we'll do the same and see if anything has changed for better or worse.
We did a fuel system pressure test at idle, and at multiple throttle pressures during a road test to see if any of the injectors were getting over or under fueled and how each injector balanced. All values were perfect (you have brand new injectors, no surprise) so we'll check those values also to see if anything has changed since the ECM reflash.
So at this moment its now the waiting game as im not the one doing the work on it, its just no ones really heard of timing going out while driving the truck. As it ran great for the first 600kms after engine swap then slowly noticed the knock under load.
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Never rule out a basic engine problem either. I know in the past (very seldom) my scan tool has lied to me about certain PID's Example is the fuel pressure on 2008 F150 reads 9psi, but actual is 43psi.
I'm not saying you're for sure experiencing a basic engine knock, but as a technician, you must always keep your mind open to explore all avenues.
Another option for you is to flash back to factory and see if the problem persists
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