Truck goes into idle with no throttle response maybe once a month now. I'd be driving normal freeway and cruising, then for no reason, the engine cuts out and idles. Pull to the side of the road and restart the engine and it behaves as nothing happened. Check Engine/MIL light is not lit.

I'm reading a bunch of posts saying replacing the throttle body is a sure fix. Before dumping $500 on something, I want to be a bit more sure there isn't a simple remedy

I dumped some logs with my AutoEnginuity reader. It shows commanded actuator is 5% but actual readings are 22%. Am I correct to interpret this as a sticking throttle plate?

I assume it's gunked up with stuff and a simple cleaning should fix it?

There's 105K on the truck if that makes any difference.

 

Has all the symptoms of a bad throttle body to me. Are you getting a wrench light at all?

Don't bother buying new. They're way overpriced. I ended up picking a barely used throttle body complete for $65 on Ebay.

That being said, in the end it turned out to be my accelerator pedal that was causing the issue, but I managed to buy both of them used. Spent all of $200 and 3-months of aggravation between them.

 

Could possibly be the TPS or the charge motor. My throttle body worked fine until I swapped those components onto a new BBK 80mm TB. At that point my troubles with those codes started. I ended up replacing both components (as a fail safe) and I haven't had any issues since.

 

I'm inclined to think @Gearbanger 101 is right. But I notice from the OP that you apparently have a reader or scanner. So but before you jump either way and spend
any money, you might glean some useful information from the rather lengthy post at: https://www.ford-trucks.com/forums/1...l#post15790594


Good luck.

 

I have an AutoEnginuity scanner with Ford extensions. No regrets!

There was no wrench light. However, getting the 2 DTC's the other day was strange. The last time, there were no stored codes whatsoever

Here I've logged the commanded and actual throttle positions and fuel pressure during some freeway driving. Both track each other fairly well. I don't see any spurious readings that would indicate a bad sensor. I think the 3 spikes were me stepping on the gas to accelerate from a stoplight. Each reading is about 300mS apart.

I had about 30K on the fuel filter; fuel pressure seemed a bit more erratic while driving earlier, but it was still within 28-40psi spec, so I swapped in a new one since it's prime time... I don't think fuel pump or pressure is an issue

I don't think there's anything suspicious here...not yet at least.

Can't fix what's not broke...

Any ideas?

 

"You can't fix what ain't broke" is certainly true. I presume the ghost did not show its ugly face during the logged freeway drive.


But I do notice a couple of anomalies (subject to two assumptions: 1) The graph Red line is Accel Pedal. and 2) Time scale is H:M:S.


Many variables exist between our different scan facilities, but my Accel Pedal readings (when I expand graphs out) seems more stable. Nevertheless - I do note that 'generally' the Red line bottoms out around 5% - EXCEPT - what happened at 06:21:42.128 where the Red line hit absolute Zero? That occurred just ahead it was "ramping up", as seems consistent with the Fuel Rail Pressure as though the Accel Pedal was headed for 70%-80% like in the other instances.

Then the Red Line "abruptly" hits ZERO, not 5%, but perhaps absolutely OPEN CKT.


This concept seems to be consistent with the Freeze Frame data in the OP. Commanded Throttle Actuator Control = 5% (Is that Accel Pedal?), Absolute Throttle Position E = 30%, Absolute Throttle Position Position = 22%. Calculated Load was 85% at 53 MPH with ONLY 5% Accel Pedal, --- REALLY. Your truck is SOME POWERFUL!! LOL


My slow methodical ways says I would clean ALL connectors / connections in the Throttle system, including the PCM plugs with a good electrical cleaner and ground connections first. And apply dielectric grease to them. If the problem reappears - then replace Accel Pedal rheostat.

 

Oh sorry...I should have clarified... the zero values at the end was me shutting off the engine when I got home :-) The continuous 20%+ throttle starting around 6:26 was a long drive up a 12% grade.

If anything, there's a bit of overshoot and undershoot on the actual throttle opening

The truck idles at 3-4% throttle opening.

I plotted accelerator sensor #1,2,and 3 including the calculated accelerator %. All seem smooth and consistent... No weird spikes or erratic behaviour on any one of them. Things drop to zero at the far right when I shut the truck down.

I'll try to reseat/clean some connectors and see if there's anything suspicious. A quick visual at them from outside looks fairly clean..No wire chaffing or oil-soaked areas.

 

I got that. I was talking about the 'momentary' glitch like dip to ZERO at 06:21:42.128.


But anyhow - I don't see anything strange in the second graph posted. Very good diagnostics capability. And I believe you are ON TO IT.


I am _attaching_ copy of a couple of portions from my Ford factory service manual that might be helpful (Partial wiring diagram covering throttle operation - and a diagnostic reference readings chart for many of the PIDs you are able to read with your scanner). The forum won't let me attach large enough files or I'd send the whole damn enchilada.


Good Luck

 

Thanks Torqued...

It did it again just yesterday and also threw a code and lit up the MIL
P0121 Throttle/Pedal Position Sensor/Switch A circuit
P2104 Throttle Actuator Control System - Forced Idle
P2111 Throttle Actuator Control System - Stuck Open
P2112 Throttle Actuator Control System - Stuck Closed

I sat parked in my driveway KOEO and slowly pressed the accelerator down and up a few times. I didn't see anything strange with the 3 accelerator sensor values--they tracked pretty consistently among each other.

However, the Throttle position desired and actual look a bit weird below at sample #17 and 43; they don't track exactly and looks like the actual is sticking, assuming the TPS is returning accurate readings.. The dark blue line is me pressing the accererator slowly up and down between WOT and not pressed at all.

Then I looked at TPS #1 and #2. TPS #2 jumps around a bit more than the other. Is it correct the two should almost be mirrors of each other? I don't have the specs to correlate.

I'm leaning toward concluding I have a flakey TPS based on this. If the throttle motor was binding, I'd expect both TPS sensors to show that, but they're not. Anything that would say otherwise?

Does anyone happen to have a pinpoint test for the TPS?
thanks!

 

@aquaman


We have here yet another example, as is often the case - I can find more things I do not know than things that I do. It looks to me as though the "Electronic Throttle Control Desired" signal should never to all the way to Zero as it appears at coordinate 17, and it otherwise never does, like at 21, 30-32 and 38-40. But I do not know if that means anything or not. Also, it may be presumptuous to think you captured an intermittent problem. However - I commend your diagnostic efforts of giving this thing very careful scrutiny before rushing into throwing parts at it.


I am attaching a section of the Motorcraft Theory of Operation covering the Electronic Throttle Control that might help shed some additional light on what causes your codes.


I assume you have cleaned the throttle body and lubricated the butterfly shaft and plate edges where it contacts the TB at closed so it does not "stick".


Other than that, after reading the "Motorcraft Theory of Operation" section, and reviewing your freeze frame data and graphs (all excellent diagnostics information), I am convinced your throttle position sensor, or the whole damn throttle body has gotta' go. The throttle position sensor has a redundant rheostat that the "E-Quizzer" processor queries the TPS and helps the PCM make the decision to trigger a code or force limp mode. I'm not even sure our scanners are fast enough to see short events that might make the E-Quizzer puke.


Good luck

 

Thanks again Torqued!
I got a new TPS part number DY1164. There are several that supposedly work with the 2005. I'm not sure what the difference is compared to the stock DY1149. Regardless, it fits. Just note which way the TPS slides onto the throttle tab on the TBS...it only works in one orientation;the throttle won't rotate in the other

I mimicked the accelerator positions from my earlier scan by pressing the pedal up and down slowly while KOEO to see what difference it makes below. TPS sensor outputs track each other much closer than the original one, like I'd expect. THe only thing I notice is sensor #2 seems to clip at ~4.5V sooner than the old one. Not sure what's with that, but I rarely drive with 60%+ throttle. I'll try it later.

When throttle_desired drops to zero, throttle_actual bottoms out at a few percent--I assume because of the idle stop? (I didn't look at it closely before I put the whole thing back together)






I did hose out the throttle body earlier but I didn't see anything that would have caused sticking

No issues,codes, or stored codes have popped up in the last 3 days, though it's still a bit early to say. Hopefully this is it...

 

@aquaman I believe you nailed it and will NOT be seeing those codes again. I commend your diagnostic mythology and persistence. Drilling down on a problem to out-smart these machines by monitoring, logging, graphing sensors & actuators while challenging their intended operation pays big dividends. I'm ashamed to admit that I made a TOO quick, snap call in post #6 that could have cost you a couple a hundred wasted bucks.


Great success story. Thanks for sharing it.

 

I'll be damned; science won this time.