cant figure this out....

I have a 94 ranger 4.0. The motor has no power on takeoff at times and idles rough. I have replaced the crank sensor, tps and mass air flow sensor plus ran a pipe through the cat,new fuel pump plugs and wires within 4k miles. I'm throwing 157,159,177 codes. thought the exhaust was stopped up but i guess i was wrong using gas like crazy. Thinking o2 sensors next. any ideas? It seems to run better in the mornings on my way to work when its cold outside around 30 degrees. The cel always comes on though when the engines hits operating temps.

157 and 159 are MAF sensor codes, new MAF doesn't mean "it works", new now means no one but you has tested it, lol.
But lets say it does work, then that leaves wiring or computer itself.
Computer is setting the 157 and 159 codes and engine is running poorly, so computer seems "sane", not saying it is, it is just acting like it is working by detecting a problem when there is really a problem.

I would check the MAF wires first, read here: http://www.therangerstation.com/tech_library/CleanMAF.shtml
About 1/2 way down there are voltages you should see on each pair of wires, I use straight pins(sewing pins) to pierce wires to test while connected.
MAF sensor can only work correctly if all the air the engine is using passes thru it, this means the big air tube connecting MAF/air cleaner to the intake must be air tight, a leak in this tube allows unmetered air in which will through off computers fuel calculations.

177 is O2 sensor not switching, computer changes fuel mix a few times a second, and watches O2 sensor changing/switching from lean to rich and back again.
As an O2 sensor gets older or gets a carbon coating on it, from running rich, it will start to switch slower, computer is seeing this so set code 177.
But if engine is running too rich then O2 sensor could just be past its limit for rich.
O2 sensor has a range of .1volt to 1.0volt, .45volt is the sweet spot the computer tries to stay around, if you are running very rich then O2 could be at .9volt and up, since it doesn't go any higher computer sees this at O2 not switching as it should.

An O2 sensor on its own won't cause your described problem, MAF can.

I would first figure out the MAF issue, you may need to pull off the computer connector and see if moisture got in there, this will cause sensor voltage to read incorrectly, as will any corrosion on wire connections.

Fuel Pressure Regulator(FPR) on the fuel rail has a rubber diaphragm that is pulled open by engine vacuum, on the 4.0l it is at the front of the lower intake passenger side.
Remove this vacuum line and check it for fuel or fuel smell.

FPR diaphragm can crack and leak, then fuel is sucked into the intake via the vacuum line causing a rich mix and very poor MPG.


A fuel injector could be sticking open, dumping extra fuel in the intake.
Try a "Clear Flooded Engine" test
Turn key on
Press gas pedal to the floor and hold it down all the way(this shuts off fuel injectors, as soon as you let off the pedal injectors will start)
Crank engine

Engine should NOT fire at all, fuel injectors are shut off
If it fires then fuel is leaking in from somewhere, could be FPR or fuel injector

The fact it runs slightly better cold means you do have a rich fuel mix, the colder the air the denser it is, so more fuel is required.

take computer out and open it. If there are any POPPED capacitors (leaking) then the computer is bad..

This page will show you what it should look like inside, also has PIN OUT designation for EEC-IV computers(1994 and earlier) and what each is for:
http://www.auto-diagnostics.info/ford_eec_iv

did the clear flooded engine test no fire until i let off the pedal. tested at the maf a-11.77 c-0.03 d-0.15 checking brain next. c sounds really low?

I unplugged the connector and every connection had corrosion. sprayed some electrical cleaner and wiped them down after i disconnected the battery will update whether its fixed tomorrow might have to replace the computer.

I was doing some reading what do you guys think about the chances of a bad coil pack? Still having the same issues taking the brain out today to check it.


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I would be a long shot, coil packs have 3 separate coils inside, each firing 2 spark plugs.
Bad coil pack symptom is usually misfire on 1 or 2 specific cylinders.
You can test coil packs with ohm meter.

Check where the spark plug wires hook up to the coil pack, make sure connections are clean.

I'm willing to try just about anything the problem was intermittent and gradually got worse the reason I ask is the other day I was on my way to work going up a long hill and my rpms started to drop. 55 in third is about 2.5k well I dropped down to second when I hit about 45 and stomped it. The rpms still were dropping and I had to pull off.


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does this look bad? My brother inlaw about has a degree in electronics but he can't be for sure cause he doesn't deal with automotive . Any opinions will be greatly appreciated just wanted a second opinion before I order one


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If your looking at the capacitor my guess is it is bad.

The difficult thing somtimes is figuring what caused it. You need to do a complete diagnostic on all the related components and wiring. You dont want to just replace the board and cook a new one as well.

Tbarnes93 said:

does this look bad? My brother inlaw about has a degree in electronics but he can't be for sure cause he doesn't deal with automotive . Any opinions will be greatly appreciated just wanted a second opinion before I order one


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Click to expand...

No, not bad yet but needs a new capacitor there.
Just a small leak of electrolytes.
Capacitors like that are rated 85deg and 105deg, make sure you replace it with a 105deg.
It will have a "u" number and "V" number on the side, you need to match those, like 10u, 50v

You don't need to disassemble anything just use a soldering iron, fine tip, and remove that one, just two wires, the stripe with the arrow show which wire goes where.
If you can remove the board to get to the back side, even better, but not required.
Get a new one, cut wires short and resolder, don't push it to far thru, don't want to short on the back side case.

Less that a dollar to replace that.

So comp wouldn't cause my flooding issue would it?


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Computer is what calculates fuel mix, so yes it could cause engine to run rich, but it is usually a input error vs computer error.
i.e. the old computer programmers saying "garbage in garbage out", while computers can get it wrong it is more likely they are working from bad data, "garbage in", when they get it wrong

Since you have the computer unplugged I would test the wiring per the link I posted, could be a short or bad wire causing the "garbage in"