random stalling issue

[red_mr2]

I have been reading everything I can today about what goes on during idle. @FordTechOne is absolutely correct regarding the oem expected idle. Something is causing the idle to drop. I am now focusing my attention on the crankshaft position sensor. Looking for a way to test it without pulling the intake manifold. I can’t find a PID specific to it in ForScan tho.

**edit** I have seen that these sensors are prone to corrosion due to their location. My tr spent its first 90k miles in Canada, so corrosion could be a thing.

if it was a crank sensor, im sure we would see some type of code. i dont think its that. my bet wiring somewhere is bad. i am gonna look to see if my ac compressor might have anything to do with it. i know its going bad but im unsure if thats the problem

 

[Gryphon313]

Guess what I found? I finally had enough time to crawl around under the truck tracing all the wiring looms. The one that runs along the driver’s side frame rail that is prone to damage at the forward cab mount was, well… damaged.

I pulled it apart and it was packed with mud. I cleaned each wire one at a time and found several that had been spliced and several that had been damaged with corrosion on the exposed wires. The one that I circled in red (Yellow/orange stripe) is the fuel pump control from the pcm.

I am still cleaning it all up and will report back after I have it all repaired. I really hope this is the problem!

 

[Gryphon313]

Took it for a drive. At first the truck ran great. I never noticed, but it would not idle forward as I released the brake from a stop before I fixed these 2 wires. Afterward, it pulled uphill as I came off the brake pedal at a stop light.

Then it happened… while I was stopped in line for gas, it throttled up on its own and tried to lunge forward into the car ahead of me. As I hammered the brake pedal to the floor it flashed the wrench symbol. After that fiasco, it kept stalling and ran rough. Power was down on the “drive of shame” home.

I checked the DTC’s when I got home and it had a P2111 “Throttle Actuator System Stuck Open” code. That would explain the incident at the gas station. I got under the truck and manipulated the repaired wires and other wires in the area with damage, but nothing happened. It does however, continue to stall at random at idle.

I am going to let it sit overnight and put the oem throttle body back on it tomorrow. I’ll do a re-learn and go from there. I am done with this demon for tonight.

 

[BenBB]

Well hell, hope the old throttle body cures THAT little trick, not cool. Also hope those damaged wires were the root cause, did it look good above and aft of that point? Was watching my tach earlier for grins, you said 600RPM is expected idle, is that what you see on the gauges? At startup mine shows about 1250 for the first ten-ish seconds and settles at 1k or just below (ambient here being 60-70°F)...

 

[Gryphon313]

Yes. At operating temp, mine idles at 600 rpm. When I hook up ForScan, it shows an expected idle of 600 rpm and usually bumps above and below that for actual rpm.

I may just buy a new rear frame wiring harness for peace of mind. I am wondering if the damaged wires need to be cut back further upstream and downstream to eliminate possible corrosion? Also, could the damage to the wiring result in damage to the components downstream? (ie fuel pump driver and fuel pump)

 

[BenBB]

Oof that seems like overkill, if you could even find one, I would be more inclined to unwind the approximately 8 miles of electrical tape on it and just visually check the insulation on each wire all the way to the connectors (and each pin in each connector). Good question though on potential damage, I would guess not, but I could very well be wrong.

Relocating that entire harness was one of the first things I did when I got mine, I mean you can see that thing just hanging down waiting to get crushed against the frame or torn loose, sure enough there were several threads on here about it happening on runs and how better to route it. Found my pics:

I forget if one roll of tape was enough or if it took several...

 

[Gryphon313]

Overkill for sure, but I count at least 2 previous repairs and my 2 repairs. It is very obvious that something hit the harness at the lowest point as the plastic loom is broken and the damaged wires were right behind it.

On another note… I captured the “ghost in the machine” while data logging. I was monitoring the Injector Power Monitor (fuel pump power is on this), Throttle Control, Fuel Pump%, Fuel Pump Monitor%, Idle, and Crank/Cam sync.

The attached graph shows where the Fuel Pump Monitor (yellow) drops out, followed by a drop in voltage at the Injector Power Monitor (green). Throttle Control (red) compensates and RPM’s (blue) jump. The Fuel Pump Monitor comes back online and Injector Power comes back up. This all occurred in a blip, but felt exactly like a stall that was caught and corrected.

At least it seems like I am honing in on the issue.

 

[BenBB]

Nice find!!! You're definitely on the right track...

 

[Gryphon313]

Nice find!!! You're definitely on the right track...

Maybe. I had several more stall events captured in the log. I had to do some reading on how the FPDM, FP, and PCM interact to understand what I was seeing in the log, but it looks like everything is doing what it should do. I just can’t tell if the culprit causing the stall is being captured. The voltage to the pump drops almost at the exact same moment the Fuel Pump Monitor starts to drop off. I can see the signal to shut the FP off, but it occurs after the stall. I checked the FP Relay, and it is staying energized during and after the stall, so power is not being cut from there.

I have read that FP’s that are in their way out can overheat and shut off. Dunno. Anyway, I cleaned all the chassis grounds and swapped FPDM’s and it still stalls, so I think it’s something with the FP if it in this circuit at all.

Thanks again fellas for all the ideas.

Still no codes.

Brad

 

[The Car Stereo Company]

Overkill for sure, but I count at least 2 previous repairs and my 2 repairs. It is very obvious that something hit the harness at the lowest point as the plastic loom is broken and the damaged wires were right behind it.

On another note… I captured the “ghost in the machine” while data logging. I was monitoring the Injector Power Monitor (fuel pump power is on this), Throttle Control, Fuel Pump%, Fuel Pump Monitor%, Idle, and Crank/Cam sync.

The attached graph shows where the Fuel Pump Monitor (yellow) drops out, followed by a drop in voltage at the Injector Power Monitor (green). Throttle Control (red) compensates and RPM’s (blue) jump. The Fuel Pump Monitor comes back online and Injector Power comes back up. This all occurred in a blip, but felt exactly like a stall that was caught and corrected.

At least it seems like I am honing in on the issue.

shit that was one of my favorite games. i was never good at it though. always hit the red line and blew up.

how is the fuse and the relocation kit? have you double checked that? also the broken wires in the drivers side wheel well, did you cut back the wires to make sure there is no corrosion when doing the repair?