My dads truck is a stock 2006 5.9l Big Horn Edition. It has 230k miles. When the engine warms up it lopes/misfires at idle. It has plenty of power going down the road just at idle it slightly misfires, from the tail pipe you can feel the air feeling choppy compared to my 5.9 at idle the air comes out smooth.

What would cause this? I already changed the fuel filer, and did a valve adjustment I .010 E .020

Any ideas? Thanks in advance.

 

You likely have a compromised injector. Hopefully it hasn't hurt the piston or cylinder. Get it checked out fast or you could have bigger problems on your hands.

 

Isn't intake and exaust pose to be .010 and .026? Anyhow, maybe the lope is the normal lope that most have that has been discussed on here several times. My 06 has loped since day one when I bought it brand new with 0 miles on it. Only does it during high idle. A LOT!!! of these trucks do it. Most just don't notice it. Atleast, I think the lope that your describing is the same one we have discussed. I could be very wrong.

 

Its not a serious lope/misfire. Its a slight lope that my dad is so picky he can notice it.

My next guess would be dirty injectors? Is there a good injector cleaner for these engines?

Also my dad says the check engine light comes on in the freeway for a mile or two them goes away automatically. Anyone have the experience?

 

You need to get the stored DTC to know what is going on. Like I said, sounds like a bad injector or possibly a harness problem. The DTC's should help illuminate the issues.

Injector cleaner as a fix for problems like this is snake oil. If the injector is bad enough to throw codes and cause issues like you describe a cleaning is probably not going to do anything but lighten the wallet.

 

The valve adjustment is .010 and .026. Just did mine yesterday. Also, yes my truck has always had a bit of a lope to it, but I would get some injector cleaner going through there just to see if it helps.

 

Well looks like I re-lashing the valves .010 .026 this weekend..and some injector cleaner shopping. Hope it helps because I dont have the bank for some new parts..

Thanks for the help guys. Cheers.