killer01ws6

all in one tank. This will be a little long but I need to give you my cars history and what has happened in the last week, so PLEASE read on and see if you can help.

I am one that checks mileage every tank, believing that if something is a miss mpg will show it first, I am one of those that normally gets 23 to 25 mpg driving 11 miles each way to work at 65 to 70 with a little in town throw in and 2 or 3 WOT per tank.

but the weekend of 5/3 I went to Fla and giving a few people a ride and playing with people, I bounded the rev limiter 3 to 4 times ( 1st and 2nd only no misses) she turned up real fast for some reason. Now I had only hit the limiter once or twice EVER before that. the drive back was fine though got 300 with that tank after getting only 60 with the 1st qtr (playing) now this tank
I have only got 120 at half, norm 200. when my wife filled it up on the 8th she called my when she got home and said I had a SES light, when I got home I checked it and it was PO420. I cleared it
it came back after trip to town, cleared it and it has not came back. But the milage is WAY off, which I did not get to upset over seeing she did not get the gas from where I normally do.

But yesterday when I went to leave work I started her and, she would only idle at 200, no shaking like missing, but I would rev a little and it would fall right back to 200, still not throwing any codes?? I drove it home pulled the same once it got rolling it seemed to bog a little in first for a sec ( could have been just me)
then fine. When I got home rock solid idle at 800 as normal.

The motor sounds great no knocks or sounds so I don't thing I got a pushrod, Bad Gas??

I live in the area of Ga that got flooded and When I was driving home from Fla I was driving in hard rain, and the gas station could have water in the gas from the rain, ( she filled up before the flood water got here, but not the rain)

I may be spassing for not, but she just seems off a little, with the codes and idle issues and all of a sudden mpg loss,

Sorry for the book but any ideas?? or help would be grateful for.

Pete

killer01ws6

come on, guys I know some of you have some idea or where to start, I would take it to the dealer for the po420, but it has not come back, and yesterday when it was idleing at 200 I didnt get a code for that either

Catskynr

No worries,
P0420 is a Catalyst Efficiency Low Fault (Bank A). What that means is this, there are four Heated Oxygen Sensors (H02S) in the exhaust system. One in front of both catalytic converters and one after. The PCM takes the O2 reading from the front sensors and compares it with the rear sensors. If the difference falls within pre-programmed parameters, the catalytic converters are deemed good. If the difference between the front and rear O2 sensors falls outside of those parameters, then the converters are deemed bad. Take for example, if there is no difference in the front and rear O2 sensors then the catalytic converter is not doing any thing. Or if there is a very large difference then it's possible the catalytic converter has a hole in it.
Now in this particular case, the PCM had come to the conclusion based on information from the front and rear O2 sensors that the catalytic converter in bank A is bad. Check for exhaust leaks. If need be, replace eithier your HO2S or probably need to replace your Cat. Bank A is the side that the #1 cylinder is on.

killer01ws6

why would it not be throwing a code now, and would that cause the low mpg and idle issue??
I guess if this is the case I will have to deal with the quirkyness till it codes again, then take it to the dealer,
Thanks,
Pete

Catskynr

When a DTC flags, which may or may not set the SES, the PCM goes into a conservative mode of operation for safety and tries to adjust the problem. This will make the engine bog and affect your mpg slightly. But, bad Cat, bad O2, bad O2 readings --- oh yea this will affect mpg, idle and performance big time.

Doc

iTrader: (9)

Hey I totally agree with all the other posts,; info regarding this question- however from reading your post again I could'nt help but wonder about the massive rain? Yes the pcm is only interpreting or looking for signals (to be relatively the same, hence the cat doing its job)before and after the cats-monitoring them- if the cat was "doused," in a rain storm that could cause a drasitic change in temp maybe that would be detected/interpreted by the pcm as a "drastic change" and set the code? Since you haven't had the code reset or stay hard since I would keep vilgant monitoring but, not worry too much.

DaddySS

How did you clear the code? When you hit the rev limiter the system dumps fuel into the cats to keep them from overheating. If you haven't reset the PCM you should start with that. If it throws the code again take it to the dealer to have them test the cat.

killer01ws6

Thanks Doc, that is a good point, I had several things all at once which is what contributed to the book type entry. I am going to let the tank get very low and fill back up where I normally do, to test the bad gas idea as I will be going back to fla this weekend so I will know if the mpg comes back and she is back to her old self.

Daddy,
I reset the code with my predator twice in the same day, then it never has came back, then two days later the 200 rpm idle thing happend once.
I drove 200 miles back home after the weekend of hitting the limiter so any dumped fuel would have been long burnt,... but the car sure seems like something it did not like is or was working its way threw the system, I will know if she is all better after this coming up trip. when you lose 150 mpg per tank in one tank you notice.

BTW well come to the board CAT and you too DOC.

and Thank all of you for the help and info, I will keep you updated. I just see so many post on people saying they get really bad mpg, and I only wanted to share that whatever is going on with my car could be a permaent prob with theres not to mention I was worried as **** about my ride
Pete