Cleaning the MAP and intake air temp. sensor
Note: I'm not recommending this. It's something I tried once, today, and it appears to have worked for me. I took a short test drive afterwards, but tomorrow will be the real test. So try this at your own risk.
My '04 SXT was idling somewhat rough and the mileage has been falling.
Talking to some mechanic friends, they recommended I check and clean the MAP sensor and intake air temp sensor, especially when I told them I was using a K&N air filter. They said the oil in those filters can coat the intake air temp sensor and skew it's readings. Also, oil from the PCV valve can coat the MAP sensor and skew it's readings.
The intake air temp sensor on my car was almost completely coated on the side of the incoming air. And the MAP sensor had a thick coating of engine oil in it.
They recommended a spray solvent made by CRC called "QD Contact Cleaner." You can get it at Lowe's and Home Depot, in the electrical area.
I got some and cleaned the MAP and temp sensor and bingo: instant smooth idle. Tomorrow I'll check the fuel economy.
They also said to use the CRC QD Contact Cleaner on the O2 sensors, if you have codes on them, before replacing the sensors. They also said to blow out the O2 sensor on the outside of the case where it samples outside air. I'll try that this weekend.
To clean the MAP sensor: remove it from the manifold and very gently spray the inside of the sensor. There is a silicon membrane in there, and another temp. sensor, according to the FSM. So just barely pull the trigger on the spray cleaner, let it fill up with the solvent, then turn it over and let it drain out. Do that two or three times, that is all it takes to remove the oil. There is an o-ring on the sensor. If it is old and not sealing well, wind some teflon pipe-thread tape around it a few times and that will ensure a good seal. Make sure the tape does not cover the opening of the sensor.
To clean the intake air temp sensor: remove the duct from the throttle body and spray the sensor. Two or three shots will remove almost any oil-based contamination from it.
The stuff dries fast, almost instantly. The can warns that the fumes are highly flammable.
Last edited by James88; 01-02-2008 at 02:56 AM.