Okay here it goes. A week before i go to get my muffler put on my C.E.L (check engine light) comes on. i got the codes read and the problem was my TPS (throttle position sensor). I replaced it, the light went out. A week later i got a Flowmaster 50 series big-block muffler put on. the C.E.L. comes on about 30 min later. i got the codes scanned about a week later.

Autozone tells my Bank 2 Sensor 2 has gone out (02 sensor). i replace it and its still on. I got the codes read again and the codes are 171 and 174. i was talking to one of the autozone employees. he was telling me that the muffler probably caused the sensors to go crazy. he said they would have a code scanner just like autozone but they can make the 02 sensors put up w/ the new muffler causing it to turn off the CEL.

I called the shop a couple days later and they tell me i probably have a vacuum leak and need a smoke test done.

Do yall have any idea wat it is?

 

Is that the one where they blow smoke in your eyes and then pick pocket your wallet?

I just did a 3" cat back on my 01 4.6l XLT and I still don't have a CEL. Maybe I'm lucky???

 

haha no.
well the exhaust shop i went to isnt that handy. they probably adjusted ur codes or something.. or maybe my truck is way messed up

 

I just put a flowmaster on mine, and the muffler comes with a piece of paper with common problems when replacing your stock muffler. The sheet says to reset your computer. Unplug the neg cable and let set for a few minutes. Your computer may have to learn the new configuration. Check out flowmasters website. There is probably something on there about it.

 

P0171 & P0174 I fixed mine by cleaning my MAF, others have had vacuum leaks at rubber elbows, other have replaced intake gaskets and the isolator bolts. do a search on those codes. start with the easiest and cheapest first. good luck, let us know!

 

i put a flowmaster super 44 on my truck and no codes. my truck did throw 171 and 174 awhile ago but it was jus a vacuum leak. i would check all the rubber elbows on your vacuum lines first cuz they are known for causing leaks. all i did to fix this was i got a piece of 3/8 fuel line replaced the elbow, and no more leaks and no more codes. good luck and i hope this helps ya

 

thank yall for the help. ill start by pulling off the negative terminal on the battery. but does anyone have a diagram where all the vacuum lines are?? and i should just feel some air coming out of the line if it has a leak?

ohh, me and my buddy checked the MAF and it seems to be working fine. i should of cleaned it when i had it out but i think its good.

 

Vacumm leaks are Extra air entering into a closed Vacuum line, Extra or too much air throws codes. You could hear a leak with a small piece of hose, run it along the vacuum lines.
But then again you could just look at them like you did with the MAF.

 

alright. how many vacuum lines are there? i should hear a hissing right?

 

yeah check all vacuum lines, pcv hoses etc. also could be intake gaskets leaking, try spraying brake clean or carb cleaner around intake area to see if idle changes, that'll let you know what's leaking. ford lean codes (171/174) can be a pain in the *** to find sometimes, let me know if you need more help, and good luck!!