06 LBZ power problems and more

[tinstar]

OK
My 06 GMC (LBZ, I think) has 123,000 miles, has had regular oil, air, fuel changes and I run Mobil Delvac in it. Engine hasn't had anything replaced.
I have run Jet fuel in it from time to time
Temps have never been close to the red
No performance mods of any kind

The problem is my loss of power and mileage degrade.

I noticed a few weeks ago that while on a flat newly paved road a slight surge/miss just as you give it a little gas from coasting. I have run several cans of seafoam and several cans of dieselKleen with no improvements.
Sometimes the surge is really bad.
The mileage is off by about 5 mpg with or without pulling my RV.

This truck used to pull my Airstream like it wasn't even there and now I have to really give it gas just to pull the long climbs. Didn't have to do that before.

I was pulling it a few weeks ago when I noticed that my check engine light was on. The next hill I barely made it up and when I floored it, I really lost power and the most I could do was 20 mph. Took the next exit and shut it down for about half an hour. Everything looked ok under the hood.
It started find and seemed to run the same as before. A little off.

It was a long trip and by the time I could get the code read, it had already shut off the DTC light.

It doesn't smoke except when you really floor it.

I have a lot of suggestions from people who really don't know diesel's. I myself don't really know much.



I hope to hear ideas from you guys that really know these things.

Thanks

[DmaxMaverick]

First, change the fuel filter. Unless the problem was there before and after the last change, the fuel filter should always be the first stop. Even if the filter is relatively fresh, it only takes one fill up with some contaminated fuel to foul it. Vandalism is also a possibility (water, etc. in your filler).

You'll need to get a scanner on it. The SES lamp indicates fresh or recurring codes. After it turns off, serious DTC's will still be stored in memory for some time. The scanner will also show EGR, MAF and turbo vane servo operation, as well as fuel pressure values. Any of these can cause the issues you are experiencing.

[tinstar]

The fuel filter was the first thing I changed and still no luck.
The air filter was next and, while dirty and needed changing, the new one didn't help. I use Wix filters.

What type of scanner?

I have a programmer for my 1998 Sierra. Will that work?
It also reads the codes, but I'm not sure about the scanner function you are talking about.

Thanks for the reply!

[tinstar]

Does that year have a catalytic converter?

If so, could that be it?

[DmaxMaverick]

It could be your cat. If you've "overfueled" for a period (used a programmer or box), it could be fouled. Possible, but not likely. I haven't heard of any significant cat problems on the late models, but that doesn't mean it can't happen.

More likely a fouled EGR, or failed/failing EGR actuator. Vacuum loss should set a DTC.

You should be able to use the scanner you use on the 98. It should at least be able to read codes. It may be able to clear them. You'll have to try it. It won't, however, be able to read real time data, such as fuel pressure regulator, and EGR operation. You'll need a Tech II (or equivalent), or a Predator programmer for that.

[Duramaster]

I have some ideas, but I need the code before I start spouting the wrong info. :D

[tinstar]

I'm on duty all week and can't get the codes read until Thurs.

No mods of any kind have been done to the engine. Bone Stock!

No fluid leaks and no hissing sound. I read in another post about that.

What should the idle exhaust flow be at the end of the pipe?

Strong or normal like a gas V8?

Thanks!

[tinstar]

I know this is stupid, but where is the egr actuater?

I'm not bad with gas V8's and turbine engines, but diesel's are a whole new ballgame to me.

[Duramaster]

The EGR actuator is on the right side of the engine compartment. Looks like a plastic motor attached to a metal housing. The assembly is behind the alternator.

[tinstar]

ok Thanks

[tinstar]

Sorry it took so long to get back.

Attached the reader and NO codes at all.

Still runs like crap