Slight miss under light throttle

[Chrono558]

Truck in question is in sig.

After the truck has warmed up and your just cruising at a steady speed, say 35mph with light throttle, it almost feels like the engine just very briefly has a cylinder drop out but it's very slight and hard to feel. It almost feels as if your pulling a trailer and getting that "push" from the trailer but it's not that severe and only feels like the engine is doing it. If you give it just a little more gas it immediately goes away. It'll return when you go back to the light throttle.

Engine overall is in decent condition. Tune-up less than a year ago (plugs, wires, cap, rotor, plug wires 7 and 8 have plenty of space between them), fuel pressure is good last time I checked it, no fuel leaking from FPR and fuel pressure did change when vacuum line was removed. Lets see, what else... TPS is about 2 years old, ECT and IAT seem to be reading right with my scanner hooked up, O2 sensor is about 1.5 years old... Only thing I noticed with puzzles me is the computer constantly going from closed loop to open and constantly switching back and forth.

I'm going to ponder on this some more. If anyone needs more info just ask and I'll supply it.

-Chrono

 

[Skandocious]

Seems strange that your computer would be switching back and forth between open and closed looped. After it enters closed loop it should stay there. How are you detecting that it is behaving as such?

 

[flareside_thunder]

Seems strange that your computer would be switching back and forth between open and closed looped. After it enters closed loop it should stay there. How are you detecting that it is behaving as such?

My guess would be his scanner.

 

[Chrono558]

Yeah the scanner is telling me when this happens. When I get a break from work and classes in a few days I'll take a video of it switching back and forth on the scanner.

 

[95F350XL]

As skan said it should stay in closed loop, maybe your O2 is acting up. We get ones from our parts store that sometimes work for a week and then take a dump. Crappy chinese electrical parts lol. Have you ever cleaned ur TB or put some injector cleaner in?

 

[Chrono558]

Sorry for the lack of updates or a video. It's midterm week here at college and my mind has been busy with studies. I'll try to get a video of what the scanner is showing in a few days.

Some more info though, the O2 is an AcDelco part. Don't start with me because at the time it was the only thing I could get. I am going to see what the ECT is showing on the scanner though and see if it is correct. Last time I had it hooked up a few months ago I noticed that the truck had a hard time getting past 184*F and staying there. I may have an issue with the ECT causing a slightly rich condition. When I get that video made I'll put it up on here and we'll figure out what's wrong.

 

[LEB Paul]

No help for your problem, but are you the same Chrono from FTE offroad a while back? Andrew?