fast idle?

[Bodaggit]

Last night I encountered an interesting problem. I have a 5-speed blazer, so when I change gears I get use to the way it feels when the rpms drop a little before going into the next gear. Last night I noticed there were times when it didn't feel right when I'd go into the next gear, so I started paying a little attention to what was going on.

When shifting gears and moving, the idle was staying up pretty high. It seemed to be related a lot to the RPM I was at when I began to shift. Mostly it would be between 1500 and 2500 rpms, and it would just stay there for a good 9 or 10 seconds before dropping back off. I went through the drive through at McDonalds, and where I was moving slow there I never had any problems with it. Then back on the road when I was getting the rpms up high enough to shift, it was again staying at those rpms and not slowing down. I went down one hill where I usually let the backpressure hold me back a lot to see if it was doing it there, and it was also holding the rpms up while in gear, anytime I let off the break it would just keep pulling me faster, instead of having the backpressure there to help hold me.

It has so far just been that one episode though. I parked it for a little while, about an hour and a half, then when I got back in it all was normal again. I don't know what it could be yet, it was as thought something got hot and was causing things to run weird for a while there.

The guages all read normal, temp was good, voltage was good, oil pressure was good. The only thing I did different before it happened was fill up with gas, at the same place I always get gas.

Any ideas?

2001, 4.3, 5-speed, stock.

No Codes

[Verto]

check for binding in your throttle body... might need to be cleaned... mine got stuck awhile ago so a pulled it and cleaned it out with some wd40, so now the valve moves freely

[billibong]

Check your throttle body. Clean it with either throttle body cleaner or carbeurator cleaner and a toothbrush - preferably an old one - cleaning out any buildup around the throttle plate. The buildup causes the throttle to stick and will sometimes hold your throttle open increasing the RPMs.
Let us know how it turns out.