First Post 1990 f150 4.9

Truck running rich won't hardly idle or run down the road.
Took it to a shop and they checked the codes and said the idle air control valve and the o2 sensor were bad.
I brought it home and changed both and that didn't fix the problem.
I read the codes myself using the check engine light flashes and this is what I got.
51 22 53 54 35 67 In that order.
This is what I have changed so far.
idle air control valve
o2 sensor
throttle position sensor
coolant temp sensor
air charge temp sensor
plugs
cap
rotor
fuel filter
different fuel
Not sure where to go from here.
Any help appreciated
Thanks.

 

Clear the codes by disconnecting the battery for at least 15 minutes, and then drive it for a while.. if it runs half decent. If it won't check your fuel pressure with and without the vacuum line connected to the regulator. BTW.. a bad vacuum leak will cause the fuel pressure to be maxed all the time which could cause your problem.

 

That's the odd thing about the codes. I disconnected the battery for about 2 hours yesterday and reread the codes before even attempting to start it to see if they cleared and the same ones were still in memory. Not sure why they won't clear.

 

That many codes, sounds like the VSS for all the sensors is kaput. Check for 5V +/- .5V DC (KOEO) at the connector for the ECT, or ACT (easiest ones to get to on the 302/5.0L). If the 5VDC isn't there, but the computer's still working, it'll flag all the sensors and allow the engine to run in "limp mode", which is to get you home or at least to the next exit. Unfortunately, even if the EEC's still functional enough to diagnose itself and the sensors, the 5 VDC comes from the EEC, and unless I'm badly mistaken, it isn't fused. You'll be lucky in this case if it's just a bad connection or loose wire. You might try disconnecting the battery, then disconnect the harness from the ECM (EEC) and check for corrosion or evidence of wires getting hot (burnt or melted insulation). And ALWAYS remember, when an EEC is telling you something is wrong, especially if a LOT of somethings is wrong, you have a sick machine diagnosing itself.

Oh, one more thing, disconnecting the battery will not clear the stored codes, or at least it didn't on my '92. I had the battery completely outta the truck for the better part of a whole day while replacing the plenum/intake gasket. I had poor performance/mileage, but wasn't setting any codes whatsoever, except when I disconnected something to check for a difference. I could make the EEC generate any code I wanted it to by playing with the sensors, so pretty much knew my problems weren't electronic. Gotta reset 'em by starting a KOEO test, then as soon as it starts to flash codes at you, pull the jumper you used to start the test while the test is running. That'll clear all stored codes. Turning the key off during the test will not do the trick.

What disconnecting the battery for an hour or so WILL accomplish for you, though, is it will force the EEC to re-learn the fuel curves. There's a good procedure or three in here for teaching the EEC your driving habits and letting it relearn the curves. Usually takes about 100 miles or so of normal driving for it to really settle in again. If the codes come right back after you reset them, then you might want to persue the 5V power for the sensors. If that checks, then sounds like the ECM stuck it's head in the dirt.

 

Thanks for the ideas, I will check the supply voltage to the sensors to night when i get back home.

 

did you try replaceing the fuel pressure regulator.