Running lean/ rough idle
03-10-2013, 05:23 PM
#1
Senior Member
Thread Starter
Running lean/ rough idle
My truck has had a little bit of a rough idle since i did the exhaust. I just attributed it to the fact that i had no o2 sensors. I put new upstreams in and the downstreams are still unplugged because i have no cats. The idle has gotten worse and it has recently developed sort of a misfire (i can hear it more than feel it because it doesnt do it when i accelerate) during low load/high vacuum situations. The codes are p0171 p1131 p0161 p0156 p0141 p0136. They basically say my o2 sensors are malfuctioning (duh) and I have a lean condition. I assumed i had a vacuum leak but i soaked the top of the motor with carb cleaner and the rpms never changed. I feel like there's something im missing. Is there a better way to check this? Do i just need a custom tune for the long tubes? Would i benefit from installing the downstreams with the gotts simulator mod? The downstreams don't meter fuel so i don't think this would matter. I aslo thought maybe i have a bad coil. Mpg is unaffected. Thanks for any help this is really bugging me.
03-10-2013, 09:39 PM
#2
I went through the same fight except I installed shorty headers. I changed Dpfe,EGR,PCV valve,went through cans of carb cleaner, changed the upper intake gasket,EGR gasket.
I found the vacuum tube on the passenger side that goes to the back of the engine was leaking through the sidewall of the tube. Replaced all of the larger vacuum tubes.
I also checked my spark plug wires with an ohm meter and I found 1 wire that was completely shot after 1 year.
The tubes that I replaced I also used aware tie to be sure that there was not vacuum leaks.
Since the vacuum tube and plugs and wires were changed it is running great. I would also check your air filter and clean the mass airflow sensor.
I found the vacuum tube on the passenger side that goes to the back of the engine was leaking through the sidewall of the tube. Replaced all of the larger vacuum tubes.
I also checked my spark plug wires with an ohm meter and I found 1 wire that was completely shot after 1 year.
The tubes that I replaced I also used aware tie to be sure that there was not vacuum leaks.
Since the vacuum tube and plugs and wires were changed it is running great. I would also check your air filter and clean the mass airflow sensor.
03-11-2013, 01:09 PM
#5
Ford Owner
Your PCM takes readings from all your sensors and calculates the correct fuel and air flow to get your engine running at the mixture where it runs most efficiently. Since you no longer have oxy sensors, it is missing information and giving you the bad codes. You really need to hook up your oxy sensors.