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92 running VERY rich especially once warm

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City, State
Houston, TX
Year, Model & Trim Level
92 2dr 5 spd
I cannot figure out what is wrong with this Explorer. I figured you guys might know...it could be something common. I am not a professional mechanic but I do work on heavy equipment on a day to day basis. My friend has this elderly couple whose 92 4.0 5 spd explorer started acting funny. It runs very rich but is driveable initially. After it warms up and you have been driving it 5-10 minutes if you give it too much pedal it will lose all power. The more you drive it the less pedal you have. Its weird though because it runs smooth right up to the limit...and the limit just gets less and less.

So they asked me to fix it. Well so far I'm already going to have to eat some of the cost because I've changed the MAF sensor and that didnt fix it. I used the old paperclip trick(though I did use wire) to pull the codes. I got a code saying the MAF sensor was out of what it expected the parameters to me. So I look at it...cleaned the pins, cleaned the maf, put it back on, still wouldnt fly so I went and bought a referb one(cant refund for my money as it had a core). NO improvement. I looked around and found quite a few leaks in the plastic piece that goes between the maf and the throttle body so I took that off taped it all up and put it back on. No fix. I thought maybe the TPS sensor was screwy so I tested it and it did have a few dead spots. Replaced that...no fix. I'm worried if i keep running it this rich I'm going to tear up some cats also...

Also took the large vacuum port off of the plastic intake line and blew in it and I can hear air coming from under the upper intake manifold but I cant seem to trace it down.

Any ideas?

Thanks,

Jonathan
 


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doonze

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'93 X Sport
Is it still throwing codes about the MAF? Is it throwing codes at all? Try this, unplug the MAF, then leave the negative cable off the battery for about 10 mins. Then fire it back up and drive it....

I'm not convinced your new MAF is ok, if your getting a MAF code, still need to check out the MAF, could be the ECM is having issues between the MAF and the computer, but if you unplug it then the ECM uses "limp home" failsafe. It uses other sensors and ignores the MAF not being there. When my MAF was bad it ran 10x better with it unplugged then it did with it plugged in. Now that I've replaced my MAF... golden.

I've heard of bad referb out of the box. One guy on here went through like 3.

Just try it, what ya got to loose?

EDIT:
Here's my thread about my MAF issues. What codes WAS it throwing?
http://www.explorerforum.com/forums/showthread.php?t=247700
 




[email protected]

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92 2dr 5 spd
Well the wires inside of the MAF that actually take the reading were build differently from the original one. I may go back and ask them to swap it. What bugs me is the timing...how it gets worse and worse the longer you drive it. Honestly I work full time and go to school full time. So I spent about 5 hours today messing with it and just gave up for the evening. I will try again tomorrow.
 
















doonze

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'93 X Sport
Not really, but MAF's do all sorts of crazy things when they go. My theory is unless they just 100% fail they start sending crazy signals to the ECU, and I'm talking CRAZY stuff, the problem is the computer believes the signals over almost any other sensor, and it tries to make everything work based on what the MAF is telling it. Then it throws all the other sensors off, and the computer tried to correct all that too. In the end, runs like crap. I've seen the MAF do some really weird stuff to these trucks.

But at least in my case unplugging it fixed everything until I could get a new MAF. Course it threw a steady CEL and was a total dog, but it ran smooth and got me where I need to go for over a month.
 




shaggymane

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91 navajo
A fuel pressure Reg running high will dump lots of fuel, run rich and will make it throw MAF codes, O2 sensor codes and a few i don't remember.

FPR should run 30 to 40Lbs.
But there wasn't anything wrong with the MAf or the o2 sensor.
 




doonze

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'93 X Sport
That's true also, we really need what code your getting, would help a bunch.

I get an O2 code (176) whenever my exhaust starts leaking (I've got a bad connection right after the cat that keeps coming undone and making the truck throw that O2 code). So just because something is throwing a code doesn't always mean anything is wrong with that sensor. Can be something else out of whack throwing the sensor off.

But I would still try unplugging the MAF, so you can rule it out. If your running rich the next logical step is investigate fuel.

Your not missing are you? If fuel checks out spark is next up on the block.
 




Maniak

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1992 XLT 4x4
If you are running really rich (black smoke etc).. Check your fuel pressure and the regulator.

If the regulator goes bad it can let full fuel pressure reach the injectors which is too much, it should be low to mid 30's. Our was 60 when the regulator went.

Also, a regulator can rip the diaphram which willl allow fuel to get sucked into the intake which will make it run rich too.

~Mark
 




GCDMD

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I'm thinking FPR too based on the symptoms. Have you also checked the temperature sender? I know when those things go, you can have very similar symptoms to what you are describing. The part is also inexpensive to boot! :D
Good luck!
 




[email protected]

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92 2dr 5 spd
hmm

Well I disconnected the maf and it did run much better(almost perfect). I took the maf I bought back traded it in for a new one and it didnt work either. So I disconnected the temperature sending unit and connected the MAF and while it didnt run perfectly it runs much better than it did with it hooked up. So I'm wondering if either sensor puts it in limp mode...I'm going to let it cool off and replace the temperature sending unit tomorrow.
 




[email protected]

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Oh and I bought a fuel pressure checker and the pressure was 30 pretty much under any conditions.
 




doonze

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The MAF unhooked for sure puts in into "failsafe" mode. I'm wondering if maybe it could be something with the PCM. Let us know how the temp sending unit replacement goes, whatever it is does seem to be sensor related.
 




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