Dad's 98 GT having not running right... need advice

[SadbutTrue]

His GT is showing a fairly substantial loss of power (had trouble getting doing basic passing and merging that it usually does). It still runs pretty smooth and the economy is about the same it usually is (19mpg overall ish). Engine doesn't seem to be running particularly hot, no missing or vibration that I can discern.

We've changed the plugs, wires, cleaned the filters, new fluids, had the transmission checked out. It sounds pretty much the same as it did before, but it just doesn't have the 'kick' when floored that it did (and yeah, I know, these GTs never had a whole ton of kick to begin with).

Its got about 120k on it, dad was thinking that the next likely culprit would be a 'clogged' or otherwise compromised exhaust. Any other ideas for what could be wrong?

 

[281CI96Coupe]

Before I even do that, I would do a compression/leak down test. Its not to hard i've heard. Then if thats it, check it off the list.

 

[N8Dogg98]

It sounds like you covered all of the basics. You may be on to something with the exhaust. My car had glasspacks on it when I bought it, and one day the power just was not there like you describe. Then a few days later I noticed that exhaust was only coming out of one side (like a riced out V-6 stang with a second tail pipe trying to appear like it was true dual exhaust). Anyways, I bought a catback and a midpipe and when I removed the stock crap, the inside of the glasspack had rusted causing the fiberglass packing to clog the exhaust pipe

Does his car have factory exhaust?

 

[SadbutTrue]

It sounds like you covered all of the basics. You may be on to something with the exhaust. My car had glasspacks on it when I bought it, and one day the power just was not there like you describe. Then a few days later I noticed that exhaust was only coming out of one side (like a riced out V-6 stang with a second tail pipe trying to appear like it was true dual exhaust). Anyways, I bought a catback and a midpipe and when I removed the stock crap, the inside of the glasspack had rusted causing the fiberglass packing to clog the exhaust pipe

Does his car have factory exhaust?

Currently it has the stock exhaust on it. My dad just mentioned that he might look at an aftermarket setup (very uncharacteristic of him... he's a stock kinda guy despite being a big car fan.. sorta rare on this site), hence the other thread.

I was also thinking it could be fuel related.. maybe soemthing to do with clogged injectors or throttle body issues (as someone who doesn't know much about fuel injection...).

I'll check the exhaust the next time its sitting and see if I see/hear something similar. Thanks

 

[bhuff30]

Replaced the fuel filter? If so, I'd start looking towards the exhaust system. It may have some clogged cats.

 

[96GT281]

ur cat might be clogged up.

 

[SadbutTrue]

ur cat might be clogged up.

For reference, we did a compression check this weekend and one cylinder was a little low (most were at 145-150psi, one was at 130).

Fuel filter and exhaust are the next guesses, I suppose.

 

[ACSPONY]

That cylinder is just about within 10% of the others, which I think is the magic number. Maybe someone can back me up on that. I would look toward the exhaust next. I think if it was a fuel issue you'd be pinging under load or when trying to pass.