1991 f150 XLT 4.9L Hesitation / stuttering

[mart1104]

I have a 1991 F150 XLT 4.9L that tends to hesitate/stutter a lot when I first start driving at about 1400-1800 rpms (primarily 25-35mph) for about 15mins or so. It feels like its cogging out sometimes to. At a idle it smells likes rotten gas and has for since my dad bought it a long time ago. I know that my girl friends dad has a F150 with the 4.9 and he said that he has the same problem with the stuttering. If I kick it down it over comes this and seems to run ok. Could it be an intermittent sensor? I also heard my brother say one of his coworkers had a 4.9 and got about 20mpg on the highway, I get about 15-17mpg is that good or bad.

[mechhound]

You don't say which transmission you have or what gear ratio your differential is, but I would say 15-17 MPG is pretty good. As for the stuttering I Would add a container of fuel injector cleaner to a full tank of gas, and give it a good ignition tune-up if you haven't done so for a while.

[transgta]

The rotten smell is more than likely the 02 sensor it can also cause stuttering. Thats where to start they can go bad and give improper readings to comp and throw many things off.