P1151, P1131 DTC's - Someone must have an answer!

Aquarius

New Member
Jul 18, 2007
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Hey guys,

I bought my 03 GT last summer and it came with BBK long tubes which I believe are the source of the problem. The CEL came on 2 weeks after I bought the car and I had to bring it back to the dealership about 5 times because each time they said they fixed it, it came back. The dealership actually outsources it's Mustang work to a local race shop and its an hour away which makes these frequent trips a real pain in the a$$. They replaced all 4 02 sensors. I do have MIL eliminators installed. After the last time the light came on (late August 07) the guy at the race shop said he was all out of answers. He put a custom chip in the car, but left the rear 02's on so I'd be able to detect any problems. I saw him the other day and he said that he legally cannot turn them off now or he'd get in huge trouble if he were caught.

The current codes are P1151 and P1131, both lean codes. Seeing as its sensing lean, is the engine now overcompensating and injecting more fuel to correct it? Is this why my gas mileage sucks (12MPG)? I burn almost a 1/4 tank of gas traveling 60 miles round trip to work everyday. One of my cats blew out last week too, perhaps too much uncombusted fuel in the exhaust melting it down? My biggest question is how can this be fixed? I was told a) either remove the long tubes and put stock headers on, or physically move the 02 sensor locations. I'd prefer not to do either of those. I know there's plenty of you out there with long tubes, so what have you done for this? There has to be an answer somewhere?
 
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A race shop caught up in legalities? What state are you located? Tell him the car is for track only and that relieves him of any issues. The only problems the rear sensors would detect is any issues with the cats. Turning them off will not be an issue if you can get him to do it. Another option is to go with a hand held tuner and do it yourself.
 
take the cats off, then go to a different shop and have your car tuned. turn off the rear O2's and you will be set.

my car doesnt have rear O2's, no EGR, no Evap system......etc. i have no check engine lights at all.


BTW the only problem the rear O2's can detect is that the cats are not working properly.
 
Aquarius:

LT's tend to leave the O2 sensors a little cooler than stock so the O2 sensor delay table should be adjusted at idle and just above. Another option is to wrap the LT's in header wrap to keep the gas hot and keep the O2 sensors perking along. This may not be the root cause of your problem but I bet heat loss is a major factor.

HTH,

Chris
 
hey man u know what i was chasing a 1131 code for 4 months after i did my engine swap. yea i went and had a diagnostic done on it and it was the freakin plug wires. i replaced so many things. i also blew one of my brand new cats out. if anything go find a local shop that works on mustangs and see if the can run a diagnostic on it. it shouldnt be no more than 125 to get that done:nice: