I have a '98 Ranger 4x2, 3.0 w/ 5 speed m/t... 150k trouble free miles ('cept for a leaky windshield)... Check engine light is on. Truck runs great, though mileage a bit down. Showing codes 171, 340, and 1131. I replaced the cam sensor a while back, though I did not change or adjust the sync. shaft as it wasn't making noise. Wondering where to begin, what to look for. I've got time, but not a lot of $! Thanks.

 

Welcome to FTE.

You may have more than one problem.

Maybe begin with a double check of the cam sensor, wiring & output signal, as the computer isn't happy with it by setting the cam sensor circuit malfunction P0340 code.

Seeing as how the cam sensor feeds the computer info on when to squirt the injectors, it might be figuring in on the other two codes which are P1131 = lack of bank one O2 sensor switching & it being stuck lean & P0171 = Bank one fuel trim @ adaptave limit.

If you can't find any problem with the cam sensor or wiring circuit, maybe try switching the O2 bank 1 & 2 upstream O2 sensors & see if the lack of O2 sensor switching follows the bank-1 sensor, as they have 150K miles on them, so they're well past time for replacement as most folks do it between 75-100K.

If no joy, maybe rig a propane sniffer using an unlit torch with tubing attached & a sports needle on the loose end as a probe & pass it around the intake manafold to see if engine idle changes, as it gets a whiff of propane. If so, try retorquing the intake manafold bolts & see what happens.

Some thoughts for pondering, let us know how it goes.

 

Thanks for the ideas. So far I have changed a dirty air filter, cleaned the MAF sensor, checked and cleaned the PCV, visually inspected the CPS wiring, vac lines etc. and swapped O2 sensors side to side. The 1131 code has swapped sides to become 1151 so... bad sensor. This code shows up consistently after very few drive cycles. CPS code 0340 has been absent until just this morning. I'm thinking this means an intermittent, unrelated problem. Yes? Also noticed when swapping sensors that the "bad" one was very sooty, while the other was fairly clean and gray. What's next?

 

Also, my '98 has a two pin CPS which I've seen listed as being for '99s and isn't the type that people often talk about exploding. My truck must be a bit of an oddball.

 

OK good test & find on the O2 sensor swap. Seeing as how they have 150K on them, replace both, as O2 sensors age their response gets slow, so you want their response to be quick & balanced for best feedback & fuel trim control. New O2 sensors will likely improve mpg & driveability.

Did you clean the MAF sensor with a non residual cleaner formulated just for that, like CRC, or Valvolene MAF sensor spray cleaner & didn't touch the sensor, or get it dirty on re-installation?????

Probably a good idea to replace the air filter. If the PCV valve was up for replacement, replace it too. Just because it rattles when we shake it, doesn't mean its good. Its spring or sealing surface can be weak & or worn, they're inexpensive, provide a calculated for controlled vacuum leak, so it needs to be working right so it doesn't mess with fuel trim, as it's air bypass isn't monitored by the MAF sensor, so this puppy needs to be working right.

Make sure you disconnect the battery B- cable to wipe the KAM, so the computer can begin to rebuild the corrupt fuel trim tables. I'd do the cold & warm idle relearn routine to avoid driveability problems.

Start it up & run it some & let us know how it goes for remaining trouble codes.

 

I cleaned the MAF with touchless spray cleaner made specifically for the purpose. How long do I need to disconnect the negative terminal on the battery to wipe it? What is the proper hot and cold idle procedure? The cam sensor code is frustratingly intermittent. I've inspected the wires, cleaned the sensor, wiggled the wires at the sensor and the PCM, poured water over it... no code, but one eventually shows up. Is the computer reading other parameters besides the actual sensor data that can throw this code? Any chance of an intermittently bad sensor? Again, this is the two wire (VR?) type. Thanks again.

 

Disconnect the battery B- cable & wait 15 min, or leave a door open, light on, push the cigar lighter in, ect to more quickly wipe the KAM.

Then replace the B- cable & do this. Ford Truck Enthusiasts Forums - View Single Post - high idle problem & let us know how it goes.

Are you certain your checking the cam sensor, its at the rear of the engine passenger side firewall.

 

No doubt it's the cam sensor I'm fiddling with. Only time I've been able to make it code is by unplugging it. Will replace O2 today and wipe it clean.

 

The 3.0L Vulcan cam sensor has a history of problems, so yes its possible that it has internal problems. Has it been making any noise lately, like squeeking sounds????

 

No noise. Drove to from Cleveland to Columbus following O2 swap. No 1131 or 1151! Looks like that's licked. Cam code is once again pending, though no MIL yet. Will check mpg on the return trip, though I'm already pretty sure it's better than it's been in a while. Is it time to throw a new cam sensor at this thing? Thanks again.

 

OK ,good trouble shooting & repair feedabck.

Any squeeking chirping sounds coming from the cam sensor when it acts out????? If so, replace it.

 

No noise that I'm catching. Replaced the sensor, cuz well, they're cheap. And... still coding with no seeming rhyme or reason. Sometimes yes, sometimes no. Will continue to try to find a pattern.