302_Mustang

I installed my new clutch and off-road H pipe at the same time. I used MIL eliminaters and after driving around about 3 days the check engine light came on. I figured it was since the MIL eliminaters weren't working properly. Then a couple days go after about 2 weeks after the check engine light first came on, I stopped at the store real quick an when I tried to turn it on it would stall out. It did this twice and on the third time I gave it gas it after that it didn't stall out anymore. I've turned it on maybe 10 times with no more problems. I figured it could be an exhaust leak at the passenger manifold flange that could cause the O2 sensor to read too lean. I used my old 02 sensors that were on the stock H pipe.

When I got it scanned at autozone the ticket said it could be vaccuum leaks, fuel leaks, misfire, but I doubt it's that since the check engine light never can on before. At this point I'm gonna buy 2 Motorcraft Upstream O2 and new passenger manifold gasket.

Anybody ever had this happen to them and found out what it was?

cliffyk

Here are the possible causes for P1131 (they are the same as for P1130), it indicates that O2 sensor 11 (passenger side front sensor) is not "switching" as it should and is stuck reporting a lean mix; an exhaust leak is the most likely cause.

Do not buy new sensors until you are certain all else is well. You can bench test a narrowband oxygen sensor with a propane torch and multimeter--here is how to do that. I would like to have 10% of the money wasted each year replacing O2 sensors that had nothing wrong with them...

supersnake67

Just an idea. Could be a coincidence or bad timing due to you doing the work but your IAC valve could be going bad..... Will cause idle issues at start up with no new codes.

supersnake67

FYI I had MILs key word "had" and my passenger side mil wasn't working right and I had a lean code. I over thought it and thought I had an exhaust leak ,but ended up being a faulty mil.

cliffyk

A bad/failing IAC will not generally cause a distinct code on a just one bank. It is possible but not likely...

supersnake67

I didn't mean that the IAC caused the code. Meant that he could have 2 seperate issues. That are unrelated.