99 Yukon sputter at highway speed?

[the 18th letter]

I've noticed on the highway or on an incline when traveling at higher speeds, if I get on the gas it responds like it doesn't know what gear to go in or can't find a gear. If I get on it from standstill or slower speeds it accelerates and shifts normally. Any ideas where to start? No SES light since about 3-4 months ago when I got a code for bad o2 sensor.

 

[BattelWagun]

I'm slightly confused, is it sputtering as in misfiring, or is the transmission constantly wandering through gears?

 

[the 18th letter]

I'm not positive but feels like the tranny to me. It will kick down but won't accelerate. I let back off it after I notice the problem. If I accelerate normally it will run all the way up odometer, only if I get on her hard will the problem occur.

 

[BattelWagun]

hmm, sounds like something in the engine, and maybe the tranny is trying to compensate by dropping gears? About how fast are you usually going?

 

[the 18th letter]

hmm, sounds like something in the engine, and maybe the tranny is trying to compensate by dropping gears? About how fast are you usually going?

I was cruising at about 70 when I got on it to pass someone. 2nd time I tried it I was going about 65 when I mashed it. It almost felt like it might not be getting enough gas. The last time it happened was under hard throttle going up a nice incline. Like before, when I let off it and eased on the gas it sped right up no problem. The reason I said tranny is because I've been noticing some hard shifts, under light throttle, out of 1st recently.

 

[SunlitComet]

plug in and see if you see a smooth full sweep signal from TPS.

 

[BattelWagun]

plug in and see if you see a smooth full sweep signal from TPS.

Thats a good start. And the 4l60E is notorious for a hard 1-2 shift. It gets worse with wear in the valve body. Mine was like that for about 40K before it failed for an unrelated reason. I think they make a shift kit that 'helps' it, but I'm not sure how effective it is.

 

[SunlitComet]

Also test your fuel pressure under various conditions.