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Leave well enough alone.......demise of an air flow sensor

1834kc

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City, State
Jasper Georgia
Year, Model & Trim Level
1991 XLT 4x4
I messed with the mass air flow sensor on my 1991 explorer (dont ask), and initially the truck ran fine, idled the same, and shifted like usual. Some time after that, when I crank it up, hot or cold, it revs really high then drops down. Also, I seem to have lost the last "shift" of the overdrive. Now the check engine light is on. In the past, that meant I was a quart low on oil, but thats fine. It takes a few seconds to come on after starting, and will occasionally go off for a few seconds while driving. I searched similar problems here, and found one problem could be the Mass air flow sensor. (surprise!) :hammer:I never would have connected shifting to that sensor, but then again, I am the one that fooled around with it in the first place. Does this sound like a mass air flow sensor malfunction? Trans fluid is clean, and it shifts very well in all the other gears.
Any help or suggestions would be greatly appreciated.
 


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huntman58

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2013 Dodge Advenger
Can not say about the shifting but when I went to a 70mm housing mine seamed to run good (with the Swiss cheesed air box) but my MPG went down or again seamed to have. I did have good power and run ability. I went back to a stock air box and MAF housing and now it runs even better. smother idle faster idle drop and back to what I used to have in MPG ( miles I can drive per every 5 gals I put in ) I can feel the power drop but I will take it for the better running truck I have now.

What you may want to try is getting a new MAF from a wrecking yard and try it to see if that is your problem. I know it took care of mine even thou they were very little ones but noticeable.
 




1834kc

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Jasper Georgia
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1991 XLT 4x4
I appreciate the info.
I forgot to mention that my gas millage has dropped also. I havent changed the air box, and the original is in good shape.
Good suggestion on going to a wrecking yard. I will try that first and see what happens. Can you tell me exactly what the sensor consists of? Is it just the black box on top of the metal housing, or does it come as one piece. I looked online for the part. One showed the whole assembly and one had just the black part with no housing.
Thanks again for the help.
 




walterd140

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'94 Sport
Check your vacuum lines for a leak / line that popped off. Not only on the tree at the head, but check the brake booster line on the side fender. That one seems hidden & can look connected when it really is not.
MAF is connected right after the air filther, 2 secure (little button in the middle) torx bolts. Check to see if the 2 wires are broken & clean. It's possible they need cleaning again
Just my 2 cents, good hunting
 




1834kc

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1991 XLT 4x4
All very good advice especially to a novice like me. Thanks.
I will check the hoses for leaks. I have had to fix one on the tree in the past. Also the booster grommet was replaced, however there are so many that are hard to see, let alone get a hand on, there very well could be a problem. The wires you are talking about. They plug into the sensor or on the inside after removing the torx bolts? It seems my sunday will be spent under and around the Explorer.

___________________________
Words to live by!!
 




1834kc

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1991 XLT 4x4
OK guys, thanks to your knowledge and willingness to share it, I think the Explorer is fixed. (that problem anyway). As you suggested walterd140, I went back and checked the vacuum hoses, and sure enough, the opposite end of the brake booster line at the tree was sucking air. The hose was too long forcing it on the nipple to far and making the end gap around the pipe. I cut off 1" and reinstalled with the factory clamp, and so far so good. Lots more power, better feeling shifts and more importantly ALL of them. I appreciate your time and getting me back on the road.
I wouldnt trade this truck even if it does look a little rough and pop and crack a little, hell, so do I.
Thanks again,
Have a safe and happy holiday!
 




huntman58

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2013 Dodge Advenger
if you ever do need to change the MAF nomaly the ones you buy at the auto parts houses are for the black box and the housing at the junk yards take your pick. that is were I got my three from as in extra black boxs and the 70mm housing plus the air box that I modded.
 




1834kc

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1991 XLT 4x4
We have a really great junk yard here that will fit the bill for my parts. However, I just discovered another issue. The radiator looks like it is filled with mud. I dont understand how it got that way so fast. No leaks that I can see, so I am going to flush and fill it tomorrow. I was assuming the check engine light was due to the vacuum leak. I guess the sludge in the radiator will cause the check engine light also? Running too hot or cold? Of coarse the gauges are the usual, "reads something different with every turn of the ignition" variety, so no help there. I'm afraid the radiator will self destruct when I clean it out.
At least the shifting is ok, and really running better. I'm still going to get the maf sensor and try it. How important is it to change the housing? Are there indications that it needs to be replaced that I can look for? I want to make sure and do what is going to get me the farthest along. Its the only vehicle I own for work and play, so its important to say the least. Once again your support is appreciated.
 




Potomac30

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IRMo, SC
Year, Model & Trim Level
1993 XLT 4WD
I got my '93 from my Dad in '04 and I had flushed the cooling system a few years prior to that because his coolant looked like Chattahoochie River water. When I got it in '04, it was dirty again and the temp gauge was staying on cold. I replaced the thermostat with an OEM unit, and a few years later it failed open/engine cold. I replaced the thermostat with a Stant and haven't had an issue since. Coolant stays nice and green, plus I drain and refill more often now with conventional green and distilled water.
 




1834kc

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Jasper Georgia
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1991 XLT 4x4
Wow! Chattahoochie River water. EXACTLY thanks for the tip on OEM and Stant. I will replace thermostat when I flush and fill and get it all out of the way.
I bought this 91 in 2009 from the original owner. It was their weekend home bang around truck. They put 10,000 miles on it in 10 years. So I have a pretty gently used 4x4 but now all the little problems start coming out. Could be worse.
 




huntman58

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2013 Dodge Advenger
When you flush and fill also flush the motor and heater core. If things are as old as you think you may want to go ahead and change out all the rad and heater hoses also.

If you only flush the rad you will leave all that mess in the motor and heater core to once again mess with ya. a good thing to also do at the same time as all of this is change out the water pump and the two sensors one for the gauge and one for the PCM. Then you will know you have a good clean fresh working system. On the thermostat you can also get a fail safe one that if it fails it fails in the open position instead of the closed. That way if it would go south you at lest have a chance of still getting down the road tell you get to were you can fix it. just a thought a bit more expensive yes but being one who used to not do it all up front it never failed down the line I was forced to do it hose at a time or part at a time but mostly a house and part at a time so now I just do it all . After 30 years you do learn a thing or two or I hope I have.
 




1834kc

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Jasper Georgia
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1991 XLT 4x4
Very sound advice. I didnt have time to get the flush kit today, but the thoughts of all that crud in there was too much. I flushed out the radiator a couple of times just to make myself feel better. The thermostat that fails in the open position should be the only one on the market. I changed out the factory clamp on the booster vacuum hose today, and fixed the end of another that goes to the tree from the cruise control. (I think). Unbelievable how those simple things impact so much. I might as well throw in an oil change while I am doing the flush. After all this, I'm golden for a while. Learning things over time is a good thing, being willing to share that knowledge for the sake of simply helping others is a great thing.
Thanks
 




walterd140

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'94 Sport
Good to hear your Explorer won't be an Exploder! Happy Holidays
 








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