My 94 seems to idle fine but when I give it throttle it bogs really bad. It started out as an occasional issue and has gotten progressively worse. So I pulled the expensive NGK plugs and put in some cheap autolite plugs as that seems to be whats recommended and the NGKs were black.... REALLY black! Could it be the coil is bad or would it be more of a fuel issue?

 

Welcome to FTE.

Sounds like an over fueling problem, lots of possibilities, so we'll need more clues to make a better educated guess on where to look next for the root cause.

SO, scan the computer for trouble codes, even if the CEL isn't lit, as there could be "Pending" codes stored that haven't turned the CEL on yet & post All code Numbers found, as they can provide good trouble shooting clues.

If you don't have or want to buy an OBD-1 code reader or scantool to scan the computer, you can pull the trouble codes yourself, by following the instructions in the "Tech Info" thread links. The Tech Info thread is located atop this forums thread listing page.

Let us know what you find.

 

Well I just did a fuel pressure test and it had 30psi the book said it should have 30-45. I also checked the vac hose on the fpr and though it wasn't very snug it hadn't come off but there was some moisture in there. But once I was done with the test and put everything back she seems to run fine so somehow by checking the fuel pressure I fixed it? I may go ahead and buy an obdI tester though. The port is under the hood on the drivers side right?
*

 

OK, good trouble shooting feedback & good idea to check fuel pressure & the vacuum hose fitting to the FPR. As they're common problem spots, it belonged on your suspect list. If the vacuum hose connection to the FPR is soft, cracked, dryrotted, ect, cut the end off so you get to better condition material for a more snug fit on the FPR, or replace the vacuum hose. If the hose was damp inside with fuel, suspect the FPR diaphragm is leaking, so consider replacing the FPR before it lays down completely on you.

 

So is 30psi too low?

 

Well it depends on how you did the fuel pressure test.
KOEO = 35-45 & it should hold the pressure for a long time, not bleed off quickly.
At idle with FPR vacuum hose connected = 25-35
At idle with FPR vacuum hose Disconnected = 35-45

I was thinking that if the FPR vacuum line was damp/wet inside with fuel, maybe the FPR diaphragm could be going bad & weeping fuel past it into the FPR vacuum line, which untimately leads to the intake manafold & that is causing the air/fuel ratio to go rich & that caused the plugs to be carbon fouled.

 

@pawpaw - would you happen to know which link that is, specifically? I've looked at every link on the "Tech Info" page and can not find a single one that states "OBD-I" - there is one for "OBD-II" and there's one for "EEC-IV" (which requires you to sign in to some AOL page) - maybe I'm just not looking in the right spot?

 

Looks like the OBD-1 link is no longer working, so try this one, as it offers up several options for reading the codes, from the blinking in dash CEL, to watching an analog meter sweep, or sub a 12 volt test lamp for the meter & count its blinks.
http://troublecodes.net/Ford/ Let us know All code numbers found.

 

So I borrowed an OBD1 code reader and it flashed code 59 which among other things could be a fuel pump issue?

 

OK, good idea to scan for trouble codes. I have the OBD-1 code 59 as an auto transmission shift problem. SO, do you have an auto tranny & if so, are you also having up shift problems that might be lugging the engine ?????

If you don't have an auto tranny, then maybe you misread the trouble code.

In any case, with the plugs being black/carbon fouled, it suggests you have an air/fuel ratio problem & a number of things can cause that.

Since you've checked fuel pressure, we know that it isn't too high, but you haven't answered the question about if the FPR vacuum line was wet inside with fuel, which if it was, would suggest the FPR diaphragm is leaking fuel into the vacuum system & it'll end up unmetered in the intake manafold causing an overly rich air/fuel mixture which will foul the plugs, all a vicious circle,l!!!!

A clogged air filter can restrict air flow into the engine at throttle up & cause it to bog down, over oiled foam or cotton gauze air filter can dirty up the MAF sensor & mess up its calibration of true airflow into the engine & mess with fuel trim, or lazy O2 sensors giving too slow a feedback to the computer for it to keep fuel trim in spec, dirty/leaking fuel injectors, or any combination there-of can cause this kind of over fueling plug fouling mischief, SO we need some more diagnostic clues to zero in on the root cause of the plug fouling problem & maybe the bog problem.

 

Yeah says it could be a Trans issue or fuel pump. New FPR and MAF.

 

Look again at the code 59 definition, if we're talking about your 94 4.0L Ranger, the fuel pump part is for an SHO, not the Ranger.

So, are you saying that you've replaced the MAF sensor & FPR???? If so, was the FPR leaking, or was the MAF sensor bad with no output, or did you just toss some parts at the problem & hope for joy?????

If you just replaced parts on a huntch, Don't throw any more parts at the problem unless you get a positive on your diagnostic testing & with good timely feedback, the forum will try to help in the interpretation of your tests, so you'll be more likely to get positive results for your diagnostic efforts.

 

Changed the FPR because I found fuel in the vac hose on the back and replaced the MAF kinda just for grins to see if it would resolve the issue and just because I'm sure it was the original from 94.

 

OK, if the FPR vacuum line was wet inside with fuel, it was probably a good idea to replace it.
Not a good idea to throw a new MAF sensor at the problem, especially if you didn't have a trouble code for it, so you don't get an atta-boy for that move!!!! lol.

When you did those repairs, did you disconnect the battery B- cable to wipe the corrupt KAM fuel trim tables, so the computer would know a repair had been made, so it could begin to build new fuel trim tables with the new parts in place????

After the KAM wipe, did you do the cold & warm idle relearn proceedure????

Did you scan for trouble codes before, or after the battery disconnect????
Do you have an auto tranny????

 

Yes I did disconnect the batter but it's possible that it was for long enough, not familiar with the relearn procedure, after the disconnect and yes unfortunately it's an auto.