New Cat?

[blackthunder]

First off, I have a 2004 GP GT

Bought the car back in May. I do approx 80% highway driving and average about 24-26 mpg. Shouldnt that be more? Im not crazy on the throttle. When I do 100 % HWY its about 26-28mpg.

Just recently I threw a P0420 and my mileage dropped to 22mpg, reset the code and its fine now.

Everytime I shut the car off i hear a lot of "pinging" right around the catalytic area. My car also take a long time to cool down too. My coolant temp is normal most of the time (another separate issue being addressed lol *cough* LIM *cough*). and its usually very hot under the hood of the car which seems a bit odd to me. Maybe thats the clogged cat cause all the heat?

Before I go dropping money I want to make sure my assumptions are correct. Went to a local shop and they want 190 installed for a magnaflow cat, which from what Ive read on here that they cause issues sometimes.

Thanks in advance!

- Trevor

[Slick2500]

As far as your gas mileage goes that sounds about right, I would start with a new fuel filter and new plugs and wires and you might see a few more mpgs.
I would say it is the cat because of the p0420 code.

[stealthee]

The pinging is just the metal starting to cool. That is normal.

Engines get hot, they take awhile to cool.

As stated the mileage is about right.

[blackthunder]

agreed that engines get hot, but this is nothing compared to other vehicles. unfortunately i cant compare to other GP's as i dont know anyone with one. But in all the cars that I have worked on, none of them took this long to cool nor be that hot under the hood.

[02NavyBlue]

In the summertime after getting home from a 40 minute drive, I literally can't touch anything under the hood within the engine bay. It weird having the fuel rail so hot it burns you, but normal. I wonder if things like the master cylinder or icm was that hot. I never really felt around to try to get burned or anything.

[Robdukes]

I also have an 04 GT and every time I turn It off I hear a pinging from near the cat. Just today I got out of the car to grab the mail and walked behind it and smelled alot of sulfur. Also noticed my transmission temperature sometimes gets up to 322 degrees when on the mountainous roads around here. Gonna have to give this thing an overhaul soon.

[02NavyBlue]

322°?? Are you sure?? That's like the transmission attempting suicide. What's the engine temp at that time? I think you meant 222°, that's pretty normal.

[stealthee]

Yeah 222* has been seen on my car climbing mountains.

[Robdukes]

haha yeah im an idiot...I meant 232..but that was after driving for awhile and taking some big hills. It was staying around 180-190 then when I took some hills 206-208 for awhile and jumped to 220-232 after a big mountain. Glad to hear low 200's is normal but I also occasionally get a delayed engage when I start from a stop(reason I was watching temp so closely). Not very often maybe happened 5 times in the last few weeks. Kinda feels like a quick burnout without the tire squealing then a light thunk and it goes.