Problems when I am going 45-60 mph
 

I have a 1994 Chevy S10 Blazer Tahoe XLT. The problem is when I am going down the road and get it to 45 mph, it starts doing, the best I can explain it is an uh-uh-uh-uh like it isn't getting gas and does it up to 60 mph. Below 45 and over 60 it doesn't do this. I had a problem before that turned out to be the connector to the fuel injector was loose and no problems after that. I have had some say it sounded like it was the fuel pump but wasn't sure. Has any one had this problem or know of some one that has had this problem and knows what it is? Also it didn't do it when I first start out only after it started warming up. Any help is appreciated. Thanks. I forgot to add it is a 4.3L Vortec V6, automatic and 4WD and has 164,000 miles.

Sounds like a weak misfire, and for that matter it could be happening all the time you just don't notice it. Check for any trouble code in your engine computer. Being a '94 it has OBD 1, so you'll need an OBD 1 compatible scan tool that works with OBD 1 GM's.

I will check that out. All I know is when I run under 45 it doesn't do it at all. If I keep gas on it it seems to not do it at those speeds I mentioned but if I try to just keep steady pressure to keep it right at 45 it does it.

I am beginning to think it is the transmission. I take it out of overdrive and put it into drive and it kinda jerks once then it doesn't do the uh-uh-uh-uh motion at the speed I indicated. I have looked all over the engine for the dipstick for the transmission fluid to check the level and cannot find it any where. Did the 94 come with a sealed transmission and no way to check the fluid level?

I'll place a bet on low transmission fluid level by about 1-2 qts. The dipstick is on the passenger side of the engine to the rear near the firewall. Mine just started doing the same thing and happens right about the same speed. I just changed out the transfer case input seal and have not topped off the transmission fluid yet.

It was 2 quarts low. I put high mileage ATF in it and test drove it after I put the two quarts in. The dipstick registered the normal level then and it quit doing it. I didn't realize it had gotten that low. I only need it to last a couple of more years until I trade it and my car in on a 4wd truck.