Hi,

I have a 95 olds 88, 3.8. 89998 miles.

When the temperature outside is hot, say over 97 degrees my car will
lose power on the highway and start to hesitate sharply. It drives fine for about 9 miles then starts to hesitate and gets worse.

Recent tune up, plugs, GM wires, fuel filter.

Could it be the fuel pump?

It runs fine when the temps are cooler.

Any ideas?

Fuel pressure is definately one of the items to be checked. Check it cold with cool weather adn check it hot with hot weather and compare the differences. Another thing to consider is it appears to be happening under load. The pump may not be keeping up with demand.

There are other things like a TB cleaning etc that might help.

Whats your temp gauge reading when things start to go south? Is the coolant level droping? Check you new plugs to see if you have any that are real white, you condition sounds like mine before the UIM gave it up. Could be a fuel issue also as mentioned. At 89k, fuel pump could be getting tired.

Whatever you do, don't do what I did and wait to fix stuff. I ended up having to have a fuel pump and a UIM replaced while on a road trip, at the dealer. Needless to say, it cost a BUNCH more to have them do it than what I could have done it for in my driveway.

The temp gauge doesn't move either direction.

I have noticed that at idle there is not much exhaust coming out of the tail pipe.

But I have not smelled the rotten egg smell of a bad cat or observed it getting red hot.

My mileage is really bad. 3/4 of a tank got me 300 miles.

It doesn't buck every day. But it loses power at any speed above light throttle.

Also, when under a load, my a/c will go from vents to floor. When the load is lessened it comes back to vents.

that sounds like a Vac problem