VCT Problem- Delay kicking in

[joezek]

Problem is on a 2008 Expedition EL, 4WD.

I'm running the Torque OBD program and have all the PID's loaded to watch the VCT settings. It's on a Droid stereo display so its easy to look at while driving.

The problem I've always had since buying the truck is that about 50% of the time when stepping on the gas, the truck just won't go, it's like it's starting off in 4th gear. Then after a few seconds it might launch like a shot of nitrous and drive normal. When monitoring the VCT duty cycle I can clearly see that the VCT solenoids are not being turned on. They are reading 0%, then when they finally get activated and jump to something like 50% the truck takes off and drives normal.

I replaced the VCT solenoids anyway and of course it didn't help. The problem is that something is causing the computer not to turn them on.

I don't really want to do all the extra work and disable them, upgrade the computer etc. if I can just figure out how the system is supposed to work and fix it.

So does anyone know what the computer is looking for to tell it to activate the VCT solenoids? There are no codes being thrown. The oil is freshly changed, VCT solenoids are new. I don't know if it could be something as simple as a bad MAF sensor giving the wrong demand settings to the computer. Or if it's because at full throttle the TPS only shows 77%.

 

[JExpedition07]

I’ll bite, almost seems like a torque converter or transmission issue. My 2007 did this at times before I replaced the torque converter. However I did replace the oil pump, chain guides, chain tensioners, etc soon after that job so it’s possible that the VCT is just working better now....hasn’t happened since all that work I did during the covid shutdown

 

[joezek]

I think that I found a clue troubleshooting the problem. If I turn off the overdrive it seems like I never have a problem. Throttle response is as expected. I don't know if it's a software issue or a tranny problem. Transmission is perfect otherwise

 

[NASCAR Mike]

I would check a few things.

TPS - throttle position sensor. These do go bad and will give bad signals to the computer where the throttle is. They don't always throw a code.
Voltage - check that you have at least 13.4 volts when the engine is running. Check grounds for proper contact. Computers are very finicky with low voltage.

I would also reset the computer. Disconnect the battery and run a fused wire from the positive cable to the negative cable for at least 5 minutes. This will clear the computer and drain the capacitors.