97 ford ranger, 148,000 miles, v6 - 4.0l xlt

Hello readers of these forums, long time reader of your wisdom and second time poster of help!

OK, so here is my sorted tail of woe and pain. Had coolant leak on my ranger, so I replaced the head gaskets and then discovered both heads were cracked; coolant leak was on both sides. So i put new heads on my ranger and replaced every gasket there was to replace and while I was at it, put a matching set of new Autolite plugs and wires on. After all was said and done my ranger still ran rough at idle and had no power to achieve 40mph without pushing it. I was at my wits end and against my better judgement took to a local mechanic.

This so called mechanic went on to diagnose me with codes 0174 and 0171; he proceeded to replace my old Bosch o2 sensors with two expensive Motorcraft sensors. According to him that removed those errors, but didn't not fix the rough idle or power loss; so he replaced the coil pack with a new Motorcraft one and he said that helped. Then he said his computer read an EGR problem, well after two weeks of diagnosing and adding parts and wanting way more money with no end in sight, i said no and took it home.

So i went on to diagnose if the EGR was the problem or not. First I replaced all the hoses running to all EGR components and the intake manifold, next i did a voltage on the EGR sensor and it read 5.5 volts; its the old aluminum one, but if im correct that should be OK? I dont have a hand vac to test accurately if the EGR valve works the way it is suppose to, its a aftermarket valve i replaced around two years, however i took the intake hose and connected it straight to the EGR and the trucks rpm changed, which if im correct is a good thing? Last night i got a error code 1504 after i replaced the EGR solenoid, now the IAC is a aftermarket component I replaced four months ago and it was very clean in the inside, but I cleaned it off anyway and then i cleared the error codes and drove around for ten minutes; the light hasn't come back on...yet. I still have no power and the idle is way better then before the mechanic, but not perfect.

Sorry for the long read, but its a long story and the more info you fine people have the more help i can get!

Summary:

Replaced the heads, all gaskets, plugs, wires, hoses, coil pack, front o2 sensors in the last month.

PS. if i unplugged the EGR solenoid and EGR sensors my truck rpm stays the same and nothing changes, good or bad ?

 

So many unknowns here that its difficult to answer your questions.

If you have an EGR, or for that matter any other trouble code, post its Number.
Work the lowest trouble code number first & work your way up the list.

It seems your woes go back to 09, when you were considering replacing the vehicles computer, but you never closed out that thread, so we don't know if you replaced it, or how the problems you were having then turned out & the computer is one of the items on the IAC P1504 trouble code suspect list!!!! So you need to find out whats going on there, as you have a trouble code for that system.

If you do have an EGR trouble code, most Ranger EGR codes are caused by the DPFE sensor, or vacuum lines to it, or carbon build up blocking the port/orifice below the EGR valve that feeds back to the DPFE sensor, so if your engine is burning oil, check the orifice out. Fords EGR valves are robust & about the only time they lay down is if they're rusty & falling apart.

When you cleaned the MAF sensor, did you use a non residual, plastic safe product whos recipe is just for cleaning the MAF sensor, like CRC or Valvolene spray cleaner & did you remove the sensor to clean it, if the vehicle had just been driven let the sensor cool, didn't poke it with the spray wand & kept it squeeky clean on installation????
Is the air tube, air box, & air filter undamaged, unclogged, seating correctly, buttoned up properly & sealing well?????

Have you replaced the fuel filter lately, or done a fuel pressure, leak down & volume delivery over time test, if so post the numbers.

Have you performed a compression, or power balance test?????

So if you can post any trouble codes & any of the above test results, we may be able to build a trouble shooting scenario to aid you in your trouble shoot.

 

Pawpaw points to a lot of good things to check. I would only add the generality that lack of power is due to lack of fuel in a high percentage of situations. Ditto on checking the fuel pressure, regulator and delivery volume.
The only other thought would be to check the valve clearance. I think you have hydraulic lifters, but when the valves were ground and seated to the seats, the effect is to lengthen the valve stem. The stem protrudes a bit higher above the top of the valve guide as the parts are ground and fitted. If you get the stem tip high enough, the valve lifter may not have enough internal travel to compensate, and end up keeping the valve from seating properly. I haven't worked on a 4.0, but if you can remove the rocker arm covers, and get some cardboard or other material to direct the oil flow back to the crankcase, you can check the valve lifter operation with the engine idling. Use a 1x1" or hammer handle to apply steady pressure down on the pushrod end of the rocker arm. A good valve lifter will allow the arm to depress slowly, and the valve will start to clack. Release the tip of the rocker arm, and the clack will diminish down to near quiet. If you cannot depress the rocker arm tip without stalling the engine {I've seen it done...}, and cannot get the lifter to compress or make the valve clatter, there may not be enough travel internal to the lifter as I described above. In the old Y-block 332-xx-427 engines, different length pushrods were available to adjust the clearance. Dunno about the 4.0
tom