Hello, first time posting here. I have a 2000 F350 4x4 Crew Long bed lifted. I do not drive the truck all that much and have been chasing an acceleration issue for about a year now. I have replaced everything from fuel to spark with motorcraft parts. TSP EGR MAF ect replaced as well.
I have recently had access to a authorized Ford IDS scantool and during the live data playback while driving under load, the PCM retards the timing at 1200 - 2000 RPM to Negative 10 degrees. Before that RPM the truck runs great. Above 2000 RPM the truck surges on acceleration all the way to 4500+. The PID's for all sensors read normal when the timing retards. The firing for all cylinders shows 100%.
For some reason, the Ford scan tool does not show a PID for the knock sensor for this VIN and the truck does have one. My first thought was a faulty knock sensor, but when unplugged, the hesitation was still there at the same RPM. I unplugged the Alternator to see if it was a "noise" issue, but the problem remains the same.
For some reason, this truck has a serious lag time to flash a CEL. It sometimes takes a day or so with sensors unplugged.
Anyway, I am leaning toward the fact that the PCM is somehow faulty and is solely to blame since I see no other PID issues when the problem occurs. What I will check next is the connector to the PCM and possible corrosion on the lead pins where there should be dielectric grease. If all is good, a reman PCM will be next.
Has anyone encountered this kind of problem with the PCM retarding the timing @ 1200-2000 RPM with all of the fuel trims and sensors showing to be within spec??? I doubt that this is a mechanical issue with timing as the engine has made no indication from noise at start up through the rpm range. If anyone can think of something I am missing here please let me know. Thank you.


Other info:
125k miles on the engine- all original
Two different Trans shops says not a drivetrain issue
Stealership states the engine is running perfect (charged me to diagnose at idle alone and not underload)
Bogs only in gear, accelerates fine otherwise
This acceleration problem used to be random but now is constant

 

Probably a Federal OBD1 calibration. Check the emissions label on the underside of the hood.


Look at your IAT value.

 

Like mentioned above the timing is being pulled because the motor thinks the inlet air temp is super high. It should be integrated into the maf so check the pinout and output voltages. You may need to replace the maf and/or check your wiring.

 

Thanks for the reply. One questions: if driving with the MAF unplugged and the same timing issue occurs at the same RPM, would the MAF still be the culprit or am I back to PCM? At this point I will try both as well as inspecting the wiring.
I have never had to replace a PCM before, does anyone know what needs to be done regarding a sync to the original? I know of the tear tag number to use when ordering, but does it just plug in? The odometer is mechanical.


Thanks for the heads up on the IAT. I seemed to have overlooked that as I was too focused on the Timing.

 

Which engine? Transmission?


You can unplug the MAF and FMEM should substitute values to make the truck run. Perhaps FMEM is seeing that IAT value and causing the timing to be pulled and causing the symptom.

 

Unplugging the maf will load a failed maf table, should run pretty poorly. You can unplug at idle and see if the IAT changes. But otherwise it's in the maf so I would start there. before the PCM.

 

Thanks to you both for responding. The engine is a 2v V10 with a 4r100 transmission. I am looking to replace the MAF first, while checking wiring, then if needed, replace the ECM. I will keep you posted with what I find. Thanks again.

 

Does anyone know if the ECM for my truck retards the timing when it senses the transmission needs to shift? Outside of the typical knock sensor input to the ECM, I cant think of anything else that could retard the timing besides maybe the ECM is receiving a bad signal that the transmission is about to shift, but it doesn't?? Or of course, The ECM is bad.

 

The sct software only shows retards for ACT, CHT, and ECT. Doesn't mean it's not there though. Did you replace the maf? My tune shows -50* at 150 ACT, max -120* at 254 ACT so if yours would be scaled to -110 or max retard.

 

Thanks for the reply. Yes replaced MAF, Wiring to ECM looks perfect (continuity / clean). Timing goes to max retard of -10 deg at the same RPM just as before. Reading on IDS software still way hot on the IAT just as before. With software on, unplugged MAF shows only a 30 degree decrease. MAF attached and compressed air to cool (not too close) and a laser reading on the MAF hot wires shows IAT to be 90 degrees, IDS stated 250 degrees. We confirmed today that the transmission is not trying to shift at the point of the timing issue.

The ECM does not throw cel's ( strike 1 )
The IAT is innacurate on the old and new MAF's (strike 2 )
The timing retards to max with no sensor fluctuation at timing retard (strike 3 )
The ECM is out.
I will post what I find.

 

It was the ECM. Replaced it and the truck runs better than it ever has. I would have never been able to track this problem down if it was not for the Ford IDS scan tool live data and the replies to this post from those who took the time to post their reply / advice on the topic.
Thank you to Toddb1 and projectSHO89 for spotting the IAT reading.
Hopefully this post will help anyone who is troubleshooting a similar condition.

 

let me start out by saying its a 2005 F350 3 valve v10 modular 6.8L with approx 160k miles. This was alleged purchased from a auction in TN. However, im thinking it might a Louisiana flood truck due to all random problems. So i pulled the dash as it recently had a stereo installed and looked for random wiring ...there is several coming off stereo... that go nowhere..

the truck has no speedometer, no odometer, no cruise and no power.. i recently changes all coilpacks and plugs..i used autolight plugs. It ran alot smoother and seemed to have little more power. But now its random codes like vss which i replaced the one on rear housing, PO500 VSS A,cps which i have replaced the one on passengerside of engine twice. DTC 5284, DTC D900, E023, DTC 9352, SC3T,PO201 INJ OPEN, Long story short its runs poorly and dont even think about hooking fifth wheel or regular bumper pull covered trailer to it... it will not make it up a hill...
please help i have jobs that i need this truck for and dont feel like losing alot More cash if i try to sell her like she is


thanks

 

just pulled the oss and vss again checked them as refered "hall effect sensors" to using volt meter set to ac waving metal in front of the sensor which checked out to be good.. it has to be a wiring harness issue.. ??