Volvo 5.7 GXIF runs rough above 4500 rpm

[Hg22]

Fuel pressure is at 36 psi on rail - new filters.
Problem is intermittent - if i unplug temp sensor while running she will turn up fine.
Replaced temp sensor - no change.
Any ideas?

 

[Don S]

Re: Volvo %.7 GXIF runs rough above 4500 rpm

Re: Volvo %.7 GXIF runs rough above 4500 rpm

Have you tried running it on a diagnostic computer?

 

[Hg22]

Re: Volvo %.7 GXIF runs rough above 4500 rpm

Re: Volvo %.7 GXIF runs rough above 4500 rpm

I have not - Is there soft ware and a harness for troubleshooting?

 

[Don S]

Re: Volvo %.7 GXIF runs rough above 4500 rpm

Re: Volvo %.7 GXIF runs rough above 4500 rpm

http://www.rinda.com/marine/mtspec.htm#techmate

 

[Hg22]

Re: Volvo %.7 GXIF runs rough above 4500 rpm

Re: Volvo %.7 GXIF runs rough above 4500 rpm

Thanks for the link - ordered the scanner ...

 

[Hg22]

Re: Volvo %.7 GXIF runs rough above 4500 rpm

Re: Volvo %.7 GXIF runs rough above 4500 rpm

Got the Rhinda scanner - neat tool but no codes even while the miss is present.
The miss is intermittent and the only thing that seems to affect it is unplugging the temp sensor - problem goes away.
Tried new sensor - no change.

 

[Don S]

Re: Volvo %.7 GXIF runs rough above 4500 rpm

Re: Volvo %.7 GXIF runs rough above 4500 rpm

You may not have a sensor failure that will show up as a code, it may very well just be something out of spec. but not to the point that it will set a code. Unplugging the temp sensor will put the ecm into default temp setting and causing the engine to run better.
You also need to be testing while the engine is running at the rpm and having the problem.
Have you already gone through the basics? Tune up, compression test, checking plug wires, etc?

 

[Hg22]

Re: Volvo %.7 GXIF runs rough above 4500 rpm

Re: Volvo %.7 GXIF runs rough above 4500 rpm

Yes, doing testing while problem occurs. The miss is very rhythmic and intermittent. Only happens above 4000 rpm. I was able to do cylinder drop test while the miss was occuring. All cylinders reacted the same. I feel as though it is a ecu guided miss. The only change I have observed on scanner during the issue is that the injector duration cycles from 9ms to 0 where it is normally stable.
Thanks for your help!

 

[Don S]

Re: Volvo %.7 GXIF runs rough above 4500 rpm

Re: Volvo %.7 GXIF runs rough above 4500 rpm

It's beginning to sound like you are hitting the rev limiter in the ECM. Did you by any chance check the rpm the scan tool was showing at the time of the miss? Was it the same as your helm tach?

 

[Hg22]

Re: Volvo %.7 GXIF runs rough above 4500 rpm

Re: Volvo %.7 GXIF runs rough above 4500 rpm

Yes, the tach matches the scan tool - it is intermittent.

 

[Don S]

Re: Volvo %.7 GXIF runs rough above 4500 rpm

Re: Volvo %.7 GXIF runs rough above 4500 rpm

Since the tach is intermittent, remove the gray wire from the tach, make sure the wire doesn't ground out and test run it.
It may very well be the tach causing your problem.

 

[Hg22]

Re: Volvo %.7 GXIF runs rough above 4500 rpm

Re: Volvo %.7 GXIF runs rough above 4500 rpm

Engine finally decided to quit running altogether - got code 81 ckp sensor - fuel and ignition ok - borrowed ckp from another engine - still code 81 and wont run. Anyone heard of the sensor wheel on crank having issues? I did remove grey wire at tach.
Thanks,
HG

 

[Don S]

Re: Volvo %.7 GXIF runs rough above 4500 rpm

Re: Volvo %.7 GXIF runs rough above 4500 rpm

There is a whole lot more to DTC-81 than just the CKP sensor. Have you followed all the troubleshooting procedures for the 81 code found in the OEM service manual?

Starts on page 413 of the manual.
Here's the manual if you don't have it. http://www.4shared.com/document/cfN9HVF3/7742218_EFI_Diagnostics.html?