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Gonna clean the MAF sensor myself

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Old 06-30-2009, 01:14 PM   #1  
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Default Gonna clean the MAF sensor myself

My car is due to be inspected in just a few days, and my check engine light has been on for ever. I got myself a OBD scanner, and the code I got was P0171 - System too lean. So, after a bunch of research on the internet, it seems that often the cause of this is a dirty Mass Air Flow sensor. Erased the code, but after a few starts, the secondary air flow system had not completed it test run (as indicated by the scanner). After another trip, the p0171 code was pending, CEL still off. Then, part way through the next trip, the light came back on, still just the one code. Very expensive part, but seems easy to remove and clean. Gotta buy some MAF cleaner, or electric cleaner, hope I can get the sensor off.

I really hope cleaning this part is the source of my problem. Wish me luck!
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Old 07-01-2009, 09:03 AM   #2  
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I've done the same thing before. The MAF cleaner is really easy. When I cleaned mine off, the error code I had cleared. Not that it's the same problem. I vaguely remember something about the O2 sensors as well. Depending on the age of the car, they might need to be replaced.
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Old 07-01-2009, 11:09 AM   #3  
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A system too lean code may mean you just have a loose hose clamp on the intake system. Clean it up and tighten them down and hopefully you just saved yourself a bunch of money! Be very careful not to damage the MAF however, like you said, it's expensive.
GL
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Old 07-01-2009, 12:29 PM   #4  
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Thanks, I'll check the hoses too. I know next to nothing about engines and cars, but am very mechanical, and won't do anything if I am unsure if what I am doing is right. But this MAF thing seems pretty straight forward. And everything I read makes it seem quite easy, but just to be careful, those connector pins are fragile, and get hot (important to make sure it is fully cooled before soaking it it alcohol.
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Old 07-02-2009, 05:59 PM   #5  
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Holy crap! Everything I read mad it seem "easy" to get to it. Took me about 20 mins just to figure out where it is, and an hour to get the thing out. I disconected all sorts of air hoses, a heat shield, etc. But it is out, and am about to soak it in alcohol. Wish me luck!
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Old 07-02-2009, 06:41 PM   #6  
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Quote:
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Holy crap! Everything I read mad it seem "easy" to get to it. Took me about 20 mins just to figure out where it is, and an hour to get the thing out. I disconected all sorts of air hoses, a heat shield, etc. But it is out, and am about to soak it in alcohol. Wish me luck!
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Old 07-04-2009, 05:55 PM   #7  
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This stuff works great.

http://www.crcindustries.com/hd/cont....aspx?PN=05110

http://www.autobarn.net/maairflsecl1.html
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Old 07-06-2009, 06:14 AM   #8  
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So here is where I am. I removed the MAF, and even took the sensor itself out of the cylinder-like housing and soaked it in a ziploc bag of denatured alcohol. One place I read said leave it for 20 mins, but I just swished it around a bit, then pulled it out with salad tongs and placed it on a towel. I then did the same with the plastic housing, just for good measure. This was last Thursday. Got up early friday and replaced everything. Took only about 20 minutes. At at the end, I had just one little clamp left over, but then quickly spotted where it belonged. Then I took a short drive to get some bagels, probably less than a mile and never got above 35mph. Starting the car seemed a little rough, almost like it would stall, but after a few seconds it smoothed out. While the drive was short, it did seem smooth. Just for kicks, I plugged the scanner in when I got to Dunkin, No codes, but all the systems were still blinking on the scanner, indicating they haven't completed their diagnostics yet.

Short drive home, same story.

Gone for the long weekend, leaving that car parked in my garage.

Took my normal commute to work today (about 11 miles, top speed probably in the range of 45mph). Again, a little rough on the start, but driving seemed much smoother. I feel like I had more power accelerating and going up hills, but was hard to tell, but the smoothness was unmistakable. Pulled in my parking lot, turned off the engine and fired up the scanner. Success! All systems finished diagnostics (especially the secondary air flow). No pending codes! I'll try and take a longer drive at lunch today. If the 2A system still works and shows nothing pending (takes 2 trip failures to trigger the check engine light), I'll be sure it all worked. Plus, I need to fill the tank, so it will be interesting to see if my mpg goes up. I have been getting between 22 to 23 on a tank.
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Old 07-06-2009, 08:13 AM   #9  
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I agree, plus the less handling the better.

Depending on the location of the sensor, fine oil spray like from over-oiled K&N filters, etc. can coat the sensor over time.
Good reason to use stock filters or dry serviceable filters (AEM or Amsoil).
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Old 07-06-2009, 12:07 PM   #10  
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Ugh. Took a nice long drive at lunch. After driving about 20 minutes, I stopped and pulled out the scanner. 1 pending code, the same as before. On my way back to the office, the light came back on. Really bummed. Not sure why the code did not come on for so long after cleaning the MAF. Chance perhaps? I sense an expensive repair in my future...
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Old 07-06-2009, 01:19 PM   #11  
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I have two Ferraris. You may need to drive up to 100 miles before you can go through all resets and clear the codes. Don't ask me why I know this. LOL
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Old 07-06-2009, 01:48 PM   #12  
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Yeah, but my OBD scanner can erase the codes, and reset all the diagnostic systems. Plus, the system that is failing, the secondary air flow system, has very specific rules as to how it triggers and clears the check engine light. 1 trip with a failed check leaves the light off, but stores the code as 'pending'. A second trip with the failed check illuminates the check engine light. Then a certain number of trips without an error will clear the light.
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Old 07-08-2009, 01:03 PM   #13  
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Here's a question. After I cleaned the MAF, I got a lon gtrip in with no light, no pending codes, which had not happened before I cleaned it. Every time I clear the codes now, I consistently get a pending code after one long trip, and the light comes on at some point during the second trip.

So, is it possible that when I cleaned the sensor, it didn't get cleaned enough? Perhaps it will be worth it to take it out again and let is soak in the alcohol for a much longer period of time. If nothing else, perhaps that will rule out the possibility of a dirty sensor causing my problems. The remaining possibilities as far as I can tell are (and probably in order of likelyhood): bad maf sensor, bad O2 sensor, bad vacuum tube somewhere, dirty fuel filter. Perhaps I should just buy the MAF cleaner, and maybe a new air filter while I am at it?
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Old 07-08-2009, 01:31 PM   #14  
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Quote:
Originally Posted by admo View Post
Here's a question. After I cleaned the MAF, I got a lon gtrip in with no light, no pending codes, which had not happened before I cleaned it. Every time I clear the codes now, I consistently get a pending code after one long trip, and the light comes on at some point during the second trip.

So, is it possible that when I cleaned the sensor, it didn't get cleaned enough? Perhaps it will be worth it to take it out again and let is soak in the alcohol for a much longer period of time. If nothing else, perhaps that will rule out the possibility of a dirty sensor causing my problems. The remaining possibilities as far as I can tell are (and probably in order of likelyhood): bad maf sensor, bad O2 sensor, bad vacuum tube somewhere, dirty fuel filter. Perhaps I should just buy the MAF cleaner, and maybe a new air filter while I am at it?
Try using MAF cleaner or if you can't get that, contact cleaner instead of alcohol. It's possible that the alcohol you used was not pure and had additives in it that have dried onto the sensor.
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Old 07-08-2009, 01:48 PM   #15  
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Try using MAF cleaner or if you can't get that, contact cleaner instead of alcohol. It's possible that the alcohol you used was not pure and had additives in it that have dried onto the sensor.
Thanks, I'm pretty sure my local Napa store should have MAF cleaner. The alcohol should have been good, though, it was "denatured alcohol" from home depot. Still, I will do it one more time, using Electrical contact cleaner or MAF cleaner.
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