Knocks and pings, blows smoke

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  #1  
Old 05-01-07, 09:48 PM
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Knocks and pings, blows smoke

I have a '94 ford explorer 4.0 V-6 engine. Whenever I accelerate to a high rpm in low gear, full throttle(it's a manual trans.) the engine pings really bad and blows this brown/gray smoke out of the exhaust. It also, of course, looses power when this happens. The guy at the garage fixed it once for me and it ran great after that. He said the airbox flow controller or sensor something or other was dirty and he cleaned it and that solved the problem.
Well it's starting to act up again and I would like to clean the airbox doohickie/thingy whatever it is myself this time.
Question is... does anyone have any idea exactly what this part is? I tried looking at the airbox and didn't really see anything I could disassemble and clean. Not sure what I'm looking for or at.
I've tried replacing the air filter and spark plugs...no change.
But it does seem like it's burning too much gas when this happens, like I have the engine choked. This would account for the brown smoke.

Does anyone have any idea??

Thanx

Jim
 
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  #2  
Old 05-02-07, 03:54 AM
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Cool smoke

Without a book on your vehicle, I wouldn't be able to tell you what the dohickey is. I do know one thing...blue smoke usually means you are blowing out oil, black is gas and white is tranny fluid or coolant. Now as far as the pinging and knocking goes, a number of things can cause pre-ignition and detination. Pre-ignition is when the spark occurs not from the spark plug but hot deposits in the combustion chamber causing the fuel-air mixture to ignite while the piston is still on the compression stroke and before the time when it is supposed to ignite from the spark plug. This pre-igintion slams against the piston and causes a ping or knock. Sometimes gasoline with not high enough octane could cause this. A cruddy combustion chamber from deposits can actually make the chamber smaller and thus increasing the compression ratio and those deposits heat up and ignite, causing the pre-ignition or ping. Sometimes the engine timing being off. The vacuum or mechanical advance in the distributor being too advanced can cause a ping. Too cold of a spark plug. Has to do with the number on the plug. For example a R43 is colder than a R45. I believe even a too rich fuel mixture can cause pings and knocks. Seems to me whoever cleaned out that dohickey only corrected the symptoms and not the problem. Were any of your spark plugs smelling of oil or gas? Also, running without a EGR valve can cause the temp to be too high in the combustion chamber and that cause pings. A number of things...I would suggest starting off with a good fuel system cleaner, check the engine timing, upgrade to a higher octane gas, and check your PCV valve by shaking it, do a engine oil change with the additive to remove gunk. Clean out the carb or throttle body, whichever you have. Check the coolant in the radiator. A hot engine will ping, also. Check the tranny fluid for signs of over-heating. It would smell burnt, it also runs through the radiator. Clear the computer codes and take it to the car wash and steam clean the engine. A dirty, greasy engine would cause excessive heat, too. Look for any crushed exhaust system parts. Excessive back-pressure might cause it, too. Good Luck!
 
  #3  
Old 05-02-07, 07:57 AM
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The do-hickey you are MOST LIKELY thinking of is the Mass Airflow Sensor. It will cause the condition/symptoms you describe. Car may run normally under light acceleration, but then spit/sputter/back-fire and/or belch dark brown/black smoke under hard acceleration.

You can try cleaning it again, but the best LONG TERM fix for your problem is going to be to replace the MAF sensor. The sensor attaches to the air-box, or more appropriately the air filter box. The sensor is designed to be self cleaning. Meaning that on every start up, or shut down, the sensor actually heats up and supposedly cooks off any contaminants that are on the sensing wire. If the heater/cleaning function is no longer working, it is allowing the sensor to become dirty and then not function properly. Again, you can clean your old one, but I would highly recommend replacing it with a new one.

The fact that you are rolling around in a '94 Ford Explorer tells me that you MIGHT not be in a financial position to fix this issue. The other alternative would be to go to a junk yard and get a used sensor off another vehicle. Hopefully the used sensor will have a functioning heater/cleaner system.

What would I do? I would use carb clean to clean the existing MAF sensor. If it fixes the problem, then you have confirmed that you need a new one. If it does fix the problem, and the car is running decent, sell it and put that $800 (good used running condition) to $1,000 (Perfect condition, never smoked in, never wrecked condition) into another car.
 
  #4  
Old 05-02-07, 09:22 AM
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Might want to examine your driving style/habits as well. You're driving a 13+ year old vehicle and doing first-gear, full-throttle accelerations to the red line; you won't have to worry much longer about the reported problem because you'll be blowing the motor in short order.

Okay, off the sopabox.

If you try the suggested MAF cleaning, there is a product desinged specifically for that. Some people have reported problems with using carb cleaner.
 
  #5  
Old 05-02-07, 10:25 AM
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No I don't even have to red line it. In fact I don't think I ever red lined it, but sometimes you do need a little get up and go on the freeway.
Also this is only a work vehicle and was looking to squeeze another year or so out of it.
It's been good to me and I will be sorry to see it go.

I will try the cleaning in the meantime.

And thank you so much for all your help

Jim
 
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Old 05-02-07, 10:29 AM
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LOL, didn't mean to preach, but it sounded like you were trying out for the Saturday night drags.
 
  #7  
Old 05-02-07, 02:55 PM
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Anyway what is the function of this "Mass Airflow Sensor"? Why does it cause such a detrimental dysfunction to the engine when it does not operate correctly?

Jim
 
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Old 05-02-07, 03:04 PM
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The MAF measures how much air is going into the engine, so the computer can adjust the fuel flow..
In order to clean it, get a set of "security allen drivers" at the auto store when you get the MAF cleaner in a spray can.. The allen drivers have a hole in the end to fit the screw that holds the MAF to the intake air tube.. It's about 2.5" square, and easy to get to..
 
  #9  
Old 05-02-07, 03:10 PM
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need to add

Be very carefull cleaning the sensor it is very fragile dont probe around in it. There are two very thin wires and if you break them you better get your wallet out.
 
  #10  
Old 05-02-07, 06:26 PM
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I do remember seeing the star/allen keys on the intake somewhere with the protrusion right in the middle. And thank you for reminding me to be careful because I do tend to manhandle delicate items sometimes. Is there something special I should buy to clean the thing like elec. contact cleaner or just regular brake cleaner.

Thanx

Jim
 
  #11  
Old 05-02-07, 06:29 PM
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either one

Either one will work brake cleaner is cheaper.
 
  #12  
Old 05-02-07, 09:00 PM
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Thanx again
 
  #13  
Old 05-29-07, 10:12 PM
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Well finally got around to getting the special wrench to take off the MAF sensor. (truck was running pretty bad)

I saw the 2 little wires you guys were talking about. (looked like a light bulb filament).One of 'em was dirty. I couldn't get it clean with a blast of brake clean, so I very gingerly dipped a q-tip in solvent and ever so gently dabbed the one with the q-tip, put it all back together and the results were like night and day.

No knock, no ping, no smoke, no hesitation, no bad gas mileage.

To think a tiny little wire could screw everything up that bad.

Just wat to say Thank You to eveyone for helping me solve this.

And just want to post back my results (which I think is a good practice).
That way someone else can learn from them.

Jim
 
  #14  
Old 05-30-07, 02:51 AM
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outstanding

Thanks for letting us us know how it worked. Dont you love these new computer cars?
 
  #15  
Old 05-30-07, 06:45 AM
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LOL...I'll have to add "clean MAF" to my list of things to perform for my next tune-up.
 
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