2007 lariat 5.4 flex. Started to buck the speed doped off but the RPMS stayed high and would follow the accelerator. The engine fail safe mode light came on and the truck would intermittently run good. When I slow down and pull off the road idles normally. Pulling back onto the road it accelerates just fine until I ease off on the accelerator. Then it starts again. During this time the tachometer is steady and follows the accelerator, but the speedometer jumps up and down. All other gauges are rock solid. CEL came on with codes P062C, P1500, P2006. Based on code P062C I replaced the output speed sensor which was no help. The alternator was producing high voltage pluses so replaced it thinking it may be confusing the ECM. Next checked all ECM inputs with no problems found.so replaced the ECM and again no joy. At times it runs just fine and will go several miles without a problem then the next time I may only get a mile or two down the road. Some times it seems like the transmission and at other time it feels like a fuel issue. Right now the plan is to check each and every wire to the ECM for wear and heat damage. Am I missing anything?

 

Crankshaft Tone ring sometimes damaged by falling plastic pieces of broken guides inside timing cover . Plastic finds its way into oil [an and jams up oil pickup resulting in low oil pressure . drop oil pan and clean out if there then timing job called for .

P2006 code is a generic OBD2 diagnostic trouble code relating to the intake manifold runner control circuit. this is a item hard to get to but has high failure rate .Its under rear of intake manifold , look for broken plastic linkage and jammed linkage . see if it will move under test . Its a bear to get to. Prime area for rodent nests .

 

The oil pressure is correct and and stable, according the panel gage. Thanks will be sure to carefully check the wires and connections you mentioned.

 

Reads mid scale for anything over 7 psi . This is truly a fraud on buyers of this truck by ford . This engine has hydraulically operated cam using dirty engine oil with poorly designed parts . Plastic guides and plastic chain tensioners with seals that blow out cause pressure problems . Plastic ends up in oil pickup causing more low oil pressure . The accountants removed steel ratcheting tensioners to save money and use very cheap plastic guides. You can use old style steel tensioners without seals to blow out but no good replacement for guides . Evidently a engine is a nuisance to ford executives ,just come up with some phony PC claims on emissions and mileage and that's it . . Engineers are capable but held back by accountants . New engines with turbines are another boondoggle .
This engine needs at least 20 psi to work well . You can add a gauge or have it checked with a external gauge . You must change oil frequently and use no more than 5w-30 . Any sludge is going to clog this system up . Use mc 820 oil filter with the good anti drain back valve . So each time you start it it doesn't have to wait for oil . One of the first things to clog up are the vcts , good idea to change them .
The oil pump is not that great to begin with . Melling just came out with a even better 340hv oil pump last fall . We had been using a better pump than factory but I would consider that one .
This lack of oil causes a great deal of problems resulting in at least a $1400 parts timing job . Any real symptoms its best to open oil pan and look for plastic guide pieces .

 

I went to the dealer the other month to have an oil pressure test done. They told me the 'oil pressure' gauge will sit just over the halfway mark at 5psi. It's not a gauge, it's very misleading.

$130 for the oil pressure test. It came back at 15psi which is when I decided to do a motor swap. If I had the time, I'd swap to the new melling HV oil pump.

 

This is fairly new rebuilt engine. Replaced last November with ab out 5K miles on it so my gut tells me it's likely a wiring problem. Your suggestions on your first post should be helpful.

 

Problem found, yea. It required removing part of the wiring harness. Turned out to be the lead from the speed sensor rubbing on the transmission dip stick tube. The wear sopt was so small it was almost impossible to spot. Have now put several miles on it under varying conditions, so i feel safe that it's fixed. Thanks redfishtd for your input.

 

Glad you gave us feed back may help someone else .