02 3.0l intermittent surging and stalling at idle
 

Hey there. New here so I’m hoping ya’ll can help me out. I’ve had this Ranger for about 3-4 months now. 2002 Ranger Edge 3.0l, 2wd, VIN: U, 126k miles, automatic. It runs and drives great except it occasionally surges at idle. Usually when coming to a stop. Always at idle, never with throttle. 9/10 times it happens when stopping or stopped. It seems like giving it a little gas stops the surging (obviously can’t always do this in the auto when I’m in traffic) It’s died on me twice now (each time a couple hundred miles apart. Both times I was able to put it in park and it started right back up. I’d say the surging is slowly becoming more frequent. However, still very intermittent. Took it to a shop and of course at that time it ran great so they couldn't replicate it.

No CEL but I scanned it and found some interesting codes. I have both P0231 “Fuel pump secondary circuit low” and P0232 “Fuel pump secondary circuit high”.

So I did some troubleshooting.

-PCM Relay: good
-PCM Diode: good
-Fuel Pump Relay: good
-Switched fuel pump relay with AC clutch relay just as an extra measure. This relay also tested good.
-Battery voltage after sitting over night with truck off: 12.6v
-Battery voltage with engine idling: 14v
-Both wires at the inertia switch get 13.8v consistently at idle
-Both wires at inertia switch get 12v for 2 seconds when turning key off to on. Sometimes it seems less than 2 seconds. I did this about 30 times. After the 12v for 2 seconds it goes to 0. It does not show 5-8v.

Not really sure where to go from here. Is it possible that the fuel pump is intermittently going bad? I know these codes are circuit codes and not fuel pump codes which is why I’m stuck. I saw another thread where someone was getting p0232 and had similar symptoms. Looks like they eventually got a lean code and ended up replacing fuel pump.
That thread is here but it appears dead as it’s from 2017

Aside from that, I listened to the injectors they all sound to be working. Another code I got is P0500 “VSS circuit failure”. Is it possible that a bad VSS is causing the surging? I have been having rough shifts recently and it’s been making some concerning grinding noises in reverse intermittently. My neighbor also mentioned he thought the fuel trim was low so I’ll include a pic. Thanks for any help in advance.
https://cimg4.ibsrv.net/gimg/www.ran...a01a911cf.jpeg

Welp. Not sure why this thread didn’t get any responses (did I post in the wrong place?) but if anyone ever happens to see this and has an idea please let me know so I can correct it in the future.

For anyone that’s finding this because you are having a similar issue, it was the VSS. I knew I had this code. But because the fuel circuit codes were coming up long before P0500 and my speedometer always seemed to work fine I assumed it was a fuel circuit issue the whole time. Easy $25 fix when ya know. It’s just hard to tell when ya don’t know 🥴

We're very limited on members, and we have very few members who know these trucks inside and out or have vast automotive diagnostic experience. That's unfortunately why your post likely received no replies, and I wish it could be different but it's simply the way it is. I've perused automotive forums for over a decade now and have seen forums that used to have tons of engagement turn into forums with the sounds of crickets.

Glad you were able to figure it out though and thanks for the update.

Not solved :(
 

Yeah that’s what I figured. Oh well, it was worth a shot.

Unfortunately this issue is just intermittent enough to have fooled me into thinking I fixed it with the VSS until driving it today. It surged on me multiple times today and got super close to stalling. P0500 (VSS circuit) code is gone. P0231 and P0232 are constant and will not erase. Guess I’ll have to post this in a couple other forums but I will come back and write if I find anything new just Incase it might help someone.

Solved
 

Ok so unfortunately the issue was the PCM. New PCM programmed in the truck and all codes have been eliminated. Has not surged on me since. As long as I don’t come back to say otherwise, problem solved.