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Discussion Starter · #1 ·
So, I just recently purchased this stang. A couple of weeks ago, it threw a CEL I think because I filled up with 93. I had the codes read and it said:

P0506 Idle lower than expected
P0420 Catalyst System Bank Efficiency below Threshold - Bank No 1.
P0430 Catalyst System Bank Efficiency below Threshold - Bank No 2.




So I cleared the codes and they did not come back for a while, I attributed it to the gas. From what I have read, stock tune should run 93 w/no problems...The other day they came back. Now....

Sometimes when i am stopped it will stall several times in a row and I have to hold on the gas to keep it started. Then other times it will run fine. I have been noticing the smell of gas at idle times (running rich?).

So today I was driving along, and I made the shift from 2-3. After I depressed the clutch, the engine started revving itself. Oddly enough, my foot was not on the gas, cruise nothing was on. I put it into gear and let the clutch out and it drove itself. Very odd and scary, felt like the gas pedal was stuck, but it wasn't. After a minute or two it stopped.


Any ideas?
 

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You really shouldn't run 93 octane on a stock tune. Its not helping the car at all..not even a little bit. And it could be hurting the car in the long run. The only way you should run higher octane is if the car makes some noise with the 87 in it. I was getting some noise with 87 and went to 89 and the noise went away. But quicky got a 93 tune anyway. Its a tapping noise like lifter noise. I would hear it as soon as i accelerated just for a second.

I cant see the octane cuase the problems you are describing. Sounds like maybe the TB is hanging, that stuff happens with aftermarket or dirty throttle bodies. Im sure a lot of other things could cuase it as well. The car is used I assume. How many miles.

So, I just recently purchased this stang. A couple of weeks ago, it threw a CEL I think because I filled up with 93. I had the codes read and it said:

P0506 Idle lower than expected
P0420 Catalyst System Bank Efficiency below Threshold - Bank No 1.
P0430 Catalyst System Bank Efficiency below Threshold - Bank No 2.




So I cleared the codes and they did not come back for a while, I attributed it to the gas. From what I have read, stock tune should run 93 w/no problems...The other day they came back. Now....

Sometimes when i am stopped it will stall several times in a row and I have to hold on the gas to keep it started. Then other times it will run fine. I have been noticing the smell of gas at idle times (running rich?).

So today I was driving along, and I made the shift from 2-3. After I depressed the clutch, the engine started revving itself. Oddly enough, my foot was not on the gas, cruise nothing was on. I put it into gear and let the clutch out and it drove itself. Very odd and scary, felt like the gas pedal was stuck, but it wasn't. After a minute or two it stopped.


Any ideas?
 

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Discussion Starter · #4 ·
Sorry, its an 2005 GT with 55k miles. Has the stock TB and I have continued using 87 and the problems are still happening. Although my light is off now....seems to be intermittent
 
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