Oil in MAF sensor (caused failure)?

[renmike]

So, I get back from out of town yesterday evening and get in my car to go to the store... It fires up, but after about 3-5 seconds, dies. I checked and made sure the fuel pump was working, then it dawned on me to look at the MAF sensor. I noticed that it had some wet oil in the side closest to the throttle body (just enough to rub off with my finger). I'm lucky that I picked up a 6-cyl Supra MAF sensor awhile back, and put it on. It started up and seems to run fine, but I went ahead and called in to work today (JMSports, I'm shipping the radio next day air tomorrow, btw). Is some oil normal? If not, what should I be looking at (pcv valve?)

[shajbot]

Yeah the front head breather line is what dump the blow-by air AND oil sometimes into the air cleaner tube (stock tube) to be burnt again. I guess too much oil was blown out and slide back onto the MAF.

What you could do is putting some kind of fuel filter inside the line or some kind of farbic even panty hose from what I read onto the fitting to prevent oil from going through while letting blow-by air escape.

[renmike]

Originally Posted by shajbot

Yeah the front head breather line is what dump the blow-by air AND oil sometimes into the air cleaner tube (stock tube) to be burnt again. I guess too much oil was blown out and slide back onto the MAF.

What you could do is putting some kind of fuel filter inside the line or some kind of farbic even panty hose from what I read onto the fitting to prevent oil from going through while letting blow-by air escape.

I'm running a cold air intake now, so the line is a little different, but I will go ahead this weekend and adapt a filter of some kind to stop some of that blow-by. Thanks!

[nikita]

If the "cold air intake" has a K&N type filter, that is your problem. The dirty secret about oiled cloth air filters is that they eventually foul MAF sensors. Ask any dealer service tech how many times they have seen this happen. The good news is that the sensor can be saved. Use a q-tip dipped in alcohol or other solvent and carefully clean the exposed wire.

[renmike]

Originally Posted by nikita

If the "cold air intake" has a K&N type filter, that is your problem. The dirty secret about oiled cloth air filters is that they eventually foul MAF sensors. Ask any dealer service tech how many times they have seen this happen. The good news is that the sensor can be saved. Use a q-tip dipped in alcohol or other solvent and carefully clean the exposed wire.

Great suggestion! I'm going to try that. In the meantime, I noticed that with the late 80's supra MAF sensor (not the turbo version, just the standard 6-cyl) the car seems to be performing much better (idling, accelerating, etc.) than it ever did with the other MAF sensor installed.

[nikita]

Oil and dirt have been building up slowly on the sensor, so you have been losing performance for quite a while. The way the sensor works is that a set electric current heats it up and air flow cools it, changing its electrical resistance. That resistance measurement tells the computer how much air, corrected for altitude, the engine is taking in. A coating insulates the wire and changes the readings.

[renmike]

Yeah I drove the car to work this morning and noticed that it ran much smoother with the new (to the car) maf sensor installed. I'll clean up the one I took off and keep as a spare, just in case.

[renmike]

Just to update, I went to the local pull-a-part Friday afternoon and picked up another MAF sensor for my Camry. It only cost me 24 bucks and came with a 30 day warranty. I went ahead this morning and took off the non-camry sensor I've been driving on for a few days to keep as a spare. So far, so good, it idles like it normally does (with the NA supra sensor, it idled about 150 RPM higher).