allthrottle&nobottle

I have a 1999 GMC NEW STYLE SIERRA 1500 2WD REG CAB SLE 4.8L V-8 AUTO 3.73 POSI EVERGREEN AIRAID RAM AIR, FLOWMASTER FORCE II CATBACK and Predator.
Over the last month at 85K it started to misfire under load, buck in OD at 50-60mph while trying to speed up and would not like to go over 4500rpm.
Started reading threads on here, LS1 & CF.
No codes, LT/STFT looked ok, O2s ok, but 8 of KR!
Regular maint is done, and I put in Rapidfires 30K ago.
Started looking for issues...........nothing obvious!
Put in new front 02s........a little better(originals any way!)
Cleaned the MAF......a little better.
Plug wires are original but read ok.....(getting some OEMs due to age & mileage)
Put in 32oz of decarb........after 2 days all is ok & no bucking
Put in fresh TR55s last night.........even better and revs normal now
KR max of 4 which is about what it always had.
Good to read prior posts..........stuff like this has usually happened before

02_2500avalanche

This is the exact problem I am having with my truck right now. Throttle response is terrible, absolutley no *****, sometimes while going it feels like I am towing a 40,000lb trailer, and it will not rev about 4k. Sometimes while ideling it will misfire and vibrate the truck pretty badly. What first came to though was the cam position sensor and knock sensor. I am going to order a new cam position sensor as these are common problems on the 8.1 but I am not totally sure what the problem is. If any one has any ideas let me know because I want my performance back.

Alex

Chevmann99

Inline Fuel Filter is the first thing that comes to mind. My 03' has 34K miles I have replaced mine twice, once at 17K miles as recomended by ProCharger when installing, and again 15K miles later as recommended by Procharger. Both times I was not having fuel pressure issues but there was a noticable restriction just blowing through it compared to new. I had a 90' 4x4 that would barely reach it's shift points at WOT and just plain ran bad with no power, changed the fuel filter and it was a whole new truck. Wouldn't hurt to run some injector cleaner through it too. Cheap and easy place to start.......

02_2500avalanche

I will throw in a new fuel filter as well. I just hope its something simple.

Alex

allthrottle&nobottle

Thanks guys,
Forgot to mention the fuel filter was the 1st thing I put on. Usually do it at 50K but I wanted to see how far I could go on OE parts..........
I though bad gas too, but it wasn't.
Seems fine now and will rev to red line w/o issue.
I had no idling problems or codes....I disconnected some stuff to see if my scan tool was ok, it was!....carbon will do that!
8.1, you need to get the codes read too see where the misfire is. I had no codes........carbon will do that

GREGGO

iTrader: (2)

Give us an update if the problems return. Sound like you guys covered evrything I could think of.

02_2500avalanche

My check engine light is not on or anything so maybe it is carbon build up. I will try running some seafoam through to see if it helps any.

Alex