98 jimmy no acceleration

Hi
i have a 98 GMC Jimmy, V6 vortec motor. I have no problems starting the vehicle or when it idels, The problem is when I am trying to accelerate or when I am on the highway. I push on the gas peddle and it makes a noise like air is escaping. It sound like it is comming from just inside the engine compartment or right underneath the floor board. It seems like it doesen't want to down shift unless I really push down on the gas peddle. I just had the tranny replaced. I also had to add more radiator fluid because it was over heating, but it doesn't look it it leaking anywhere. Any help would be great. I am on my wits end and am about to just get rid of the vehicle becausr of all the problems.

Thanks
Chris

It sounds like an exhaust problem, something clogged. It sounds like the catlythic convertor partially clogged. When you step on the gas you hear the backpressure trying to escape, but it cannot get through the cat fast enough. Its alright at idle, because not as much air volume going through the engine. Did you ever recently have a misfire? Coolant in the exhaust will also destroy a convertor too, but if you are having coolant in the exhaust, thats another problem in itself too....

I don't think that I had a misfire, but how would I know if I did have one. Also how would I check if there was coolant in the exhaust??? I am trying to figure out if I should put some more money into it or just get rid of it???

You would feel a misfire when your driving as like a skip in the engine, especially under load, plus the service engine light would start to blink informing you of a misfire. You mentioned you had to put coolant in the system, yet you saw no visible leaks under the truck. The coolant could be leaking inside the engine, and be burnt during combustion. That would destroy the convertor, and clog up the system. How amny times have you had to refill the coolant system? Check around the intake gaskets and see if they are weeping or wet, indicating a leak. Hope this helps...

try replacing it or you can eliminate it completely. That's what I did. Got all my power back! Be careful of the smog laws in the state where you live, you may need a catylic converter on there. Just a possibility. I had the same signs and symptoms and a hunch, so I chopped off the converter. Runs Great! Keep at it, you'll find your problem!

You cannot just chop off or gut the cat on OBDII systems. The system is designed to monitor the effeciency of the convertor. When you take the cat out, the computer will light up the Service Engine light because it will sense that there is no difference from the O2 sensor readings from before to after the cat. You can drive it, but the Service Engine light will come on and stay on until a new convertor is installed. Either way, if thats your problem, you have to get a new convertor.

Check for vacuum leaks.

Sounds like a vacuum hose has come off.

That , or your cat is plugged.