• Welcome to The Truck Stop! We see you haven't REGISTERED yet.

    Your truck knowledge is missing!
    • Registration is FREE , all we need is your birthday and email. (We don't share ANY data with ANYONE)
    • We have tons of knowledge here for your diesel truck!
    • Post your own topics and reply to existing threads to help others out!
    • NO ADS! The site is fully functional and ad free!
    CLICK HERE TO REGISTER!

    Problems registering? Click here to contact us!

    Already registered, but need a PASSWORD RESET? CLICK HERE TO RESET YOUR PASSWORD!

Loping or surging at idle...it seems like my truck has a big cam in it.

BudTX said:
Is it the variable vane turbo that you hear? The exhaust note will change pitch at idle, but there is no change in rpms if you watch the tach.
Click to expand...

Nope, it's not that. I can watch the rpms go up and down slightly and feel it vibrate in the seat. The rpms change by 100-200. It seems to do it in 3-5 second spurts, then goes away, then comes back.. etc. Instead of the steady shhhhh sound from the turbo it goes more like shh shh shh then normal. Sometimes the vanes will adjust and I'll hear the lower grumble with less turbo noise...that's not what I'm referring to.
 
These new fuels do not have enough lube in them as far as I am concerned. Thats why the bio mix helps as well. I put a full quart of ATF in every 5th tank. No high dollar stuff just the cheap stuff. I had 2 injectors go on my LLY with less than 20K on the clock. I've been doing it ever since then and it runs better and smoother each time after about a half of the tank with ATF has gone through. While they say you should not have to do it for the 2 bucks and the nicer running I not going to change anytime soon.

I've had several people with issues on LLY's and once they start on the ATF they have gone away. I always tell them 1 quart in every tank for 5 tanks. If it settles down then cut it back to 1 every 2. As long as its running still good then cut back to every 3rd and so on, till you get to one in every 5.
 
Mine did not start out with a big lope. Mine was just a slight idle change. Just like you described...
 
BudTX said:
I still suspect the fuel pressure regulator.
Click to expand...

I feel the same but I wrote that on a slip of items for him to check. He supposedly went through the fuel system. Do you think if I replace the regulator and the problem went away that they would reimburse me for it?

I have my Predator...is there a way to check the diagnostics on that if the fprv is within spec?
 
Well, anything real close closed and this one stayed. They're supposed to have a good diesel tech, plus they don't care about my mods...not sure about the other ones. I haven't heard great things from the other ones my buddies have gone to. Maybe I'll call back or stop in if I get time and talk to the tech who worked on it.
 
Well I talked to the Diesel tech at the dealer for about 20 minutes. He says he's done all the tests and can't find anything else wrong. I've had a mas air flow sensor code since I put the Pred in 2 years ago but didn't always notice the lope. I don't think it's that code making it do that. The truck does it with or without the stock program.

The tech says that he thinks with that code thrown that the programmer made the ecm think it was a round filter and not the square one. He says my programmer has locked out the ecm and won't let him reprogram it...but then he says he can wipe it clean and start over but it will do the same thing once I put my programmer back in. He doesn't think it'll hurt the motor running the way it is now. I don't like it though, the more I think about it the more I want it fixed. I want this truck to last a long time and I want it running like it should.

Is it even possible my Predator has locked out the ecm from him reprogramming it because that doesn't make sense to me. He tries programming it with a computer (not tech 2) and when he tries it comes up with "unknown error" or something to that effect. I brought it in with the factory settings and totally unprogrammed from the Pred.
 
Diesel Tech said:
These new fuels do not have enough lube in them as far as I am concerned. Thats why the bio mix helps as well. I put a full quart of ATF in every 5th tank. No high dollar stuff just the cheap stuff. I had 2 injectors go on my LLY with less than 20K on the clock. I've been doing it ever since then and it runs better and smoother each time after about a half of the tank with ATF has gone through. While they say you should not have to do it for the 2 bucks and the nicer running I not going to change anytime soon.

I've had several people with issues on LLY's and once they start on the ATF they have gone away. I always tell them 1 quart in every tank for 5 tanks. If it settles down then cut it back to 1 every 2. As long as its running still good then cut back to every 3rd and so on, till you get to one in every 5.
Click to expand...

Thanks for the tip. I am on my first tank and drove about 350 miles to my original dealer to have them replace the speedometer cluster and told him about what I was doing. He has a 2005 LLY and has put in two FPR's in his. He sees no need to replace the FPR as it will be ok for awhile then start all over again. GM has no clue as to what the REAL problem is. I think that you might be right about the new fuel as I didn't have a problem until the NEW fuel became the only one you can get....
 
You must log in or register to reply here.
Back
Top