Hey all,

Im new to the forum, but this ranger I bought last year is the fourth one I’ve owned, first 4.0. I’ve had misfire or wonky idle issues on my 3.0s and it figures this 4.0 would give me similar issues.

Truck runs great at first from a cold start, and most of the time when driving light on the acceleration.. after it warms up if I punch it and get the rpm’s up over 2600 the truck has some bucking/surging, most noticeable on decel and when coming to stop it has even stalled. I’ve checked the o2 sensors through my scanner and bank 1 sensor 1 runs like it should most of the time spiking hi-lo between .1 and .9, but will occasionally get stuck at say .7 or .1 for up to a few minutes. I’ve also seen it drop to 0. Then I noticed that bank 1 sensor 2 would also go from running normally (steady trend around .8) and then drop to 0. On one occasion the MAF sensor also dropped to 0. I hate to think pcm issue but that’s a lot of wonky sensors.

The main DTC that keeps coming up is p1131 for lack of o2 sensor bank 1 sensor 1 lean, but I’ve also had p1132 once(rich), and p300 once(random misfire). While trying to pinpoint the issue I’ve checked fuel pressure which wasn’t holding pressure, so it has a new fuel pump. The valve cover gasket had an oil leak so it has new upper intake gasket and valve cover gaskets. There was an exhaust leak after the rear cat that I don’t think would be related, but after messing with the clamps it’s now minor. After reading up on dpfe sensors I opted to try and unplug the sensor which did seem to improve drivability while unplugged, but I installed a new one and the issue remains. The previous owner had replaced plugs, wires, and iac. Any ideas?

 

how many miles on the odometer. sounds like O2 sensors

 

156k ish. I had ordered a new upstream for bank one and went to install it and it looked identical (the one on the truck looked relatively new) and for some reason I feel like the previous owner had replaced it but I can’t be sure. I had returned it at that point but for piece of mind I should probably replace it. Downstream one I replaced and then got 0v realizing there’s a bad wire somewhere in the harness. I wiggled the main harness side and realized it would start and stop reading when I moved it around. I’ll have to chop the wiring up and replace a portion it.

 

the down stream sensor has nothing to do with the motor, the 2 upstream control how the motor is running , right bank and left bank. they need to be replaced every 10yrs or 100k mi. they start to work when the motor is at running temperature. if you had a code of running lean on one bank it could be an O2 sensor not telling the PCM the right information.

read this post
https://www.ranger-forums.com/2-9l-3...m_content=post

 

Thank you, sometimes my mind goes faster than I can fix things and forgets these things. Should’ve realized downstream is just monitoring efficiency of the cat. New bosch upstream sensor will be here tomorrow and I’ll go from there.

 

if the new sensors dont fix the issue, the motor will like it.

 

I replaced bank 1 sensor 1 after fighting with it for a day, came out with no thread, had to use a tap and thread chase to get the new one in. Then it misfired consistently. I started pulling plugs and wires out of frustration and the previous owner managed to break a wire when replacing them and installed an assortment of copper and platinum plugs with different gaps everywhere. After installing new double platinum autolite plugs and fresh wires she’s a lot happier. Don’t trust your sellers lol.

 

not sure but on a 3.0 the passenger side is much easier , driver side i cut a hole in the plastic finder well to get to it.