When its going bad? I have the rotten egg smell but only on hard accelerations and WOT. Here is the deal my in town gas mileage sucks:
1. I have done the tune up minus fuel filter because I cant find one, (flex fuel 3.0)
2. I have cleaned the MAF
3. Changed my driving habits in town
4. Began running different Gas (went from BP to Shell)
5. Had my exhaust checked.
6. Tires are inflated properly
7. Oil Change with Mobile 1 every 5,000 Miles

I am not a mechanic or anything but I do know that 11 MPG in the city and 15MPG on the highway isn't right. My truck just started doing this about 4 months ago and I have 55,000 miles on her now. I need as many suggestions as you can come up with that are realistic please.

 

I don't know anything about the cats but

I had trouble getting the right fuel filter for my flex fuel engine. Yours has 2 inlets and one outlet correct? Every time I went to autozone or advance they would give me one that had 1 inlet and 1 outlet. I told them to try searching for just a regular 3.0L and they gave me one with 2 inlets and one outlet and it fit perfectly. I have no idea why its like that but I have had it on my truck for a while now and it did help gas mileage.

 

Easiest way to tell if your cat is bad is by having someone follow you when your engine is fully up to temp and floor it a few times letting the motor wind out. You will get a rotten egg smell from the exhaust if its bad, and the smell will be obvious.

 

I found the right one at Autozone they ordered it took my money and sent the wrong one 4 weeks later I had the hardest time even getting my money back. I will try Advanced 'today and possibly Oreily's.
Still looking for answers to Cats though.

 

Ok then they are bad so how do I know which of the 6 is bad? Also where can I buy them and if you say the dealership then I am screwed. This is beyond me here. So HELPPPPPPPPPPPPPPPPPPPP!!!!!!

 

if you hafta get a new cat, id suggest getting a universal high flow cat. They can be cheaper than stock ones and they flow better.

 

Ok then link me LOL I can't find anything,

 

Yeah, most likely it is the last (and largest) one, so I would just get a magnaflow high perf. cat and have a muffler shop weld it in. I know the one on my Bonneville was 80 some dollars. check out this site. http://www.justmagnaflow.com/

 

The rotten egg smell does not mean that a cat is bad. It means that the exhaust mixture is overly rich. That seems to fit with your loss of fuel economy too.

I would have a shop check the fuel trims to see if you are way off to the rich end. There are many reasons why your truck could be running rich - MAF sensor, oxygen sensors, misfire, fuel pressure wrong, just to name a few. These may or may not give you a CEL immediately.

 

Hummm Well I have no CEL just a loss of economy and a little power loss which just kills the 3.slow even worse than normal.

 

I know that when I changed it on my bonneville the smell went away, but then again, the car is a 92 so it was probably due...lol.

 

Can this happen just over time? I mean no one has been under the hood except for the tune-up? Or could it mean worn out parts? Damn why isn't one here that knows this chit in the area. I am broke already and don't want to pay someone to lie to me.

 

I just got a report that my cat. was bad so they are supposed to fix it. i didnt smell no rotten eggs???

 

Vacum leak - Hints on where to look for this please?

 

I had one cat go bad. It was basically clogged and the truck wouldn't go past 40 mph. The code that popped up was cylinder missfires. Makes sense since no exhaust out = no air/gas in.

 

All of that has been checked. No vacum leaks detected, no CEL and a hellua lot rotten egg smell when I romp it ??////

 

I don't believe anybody mentioned this, but if your problem was indeed the catalytic converter(s) wouldn't they be covered under emissions warranty?