I've read most of the posts on the forum concerning compromised gas mileage. Seems the most obvious is the o2 sensor.
Here's what I've done recently. I thought I should start work on the mass air flow sensor. Well, Murphy and ignoramus here pulled the wires out of the Mass Air flow sensor..big mistake...I got it back together, but still need to solder some of the connections back. While I had the top off the sensor, I noticed that it rotates and opens the air intake as the engine rpms increase. I also noticed the inside of the air intake had a lot of oil residue in it where the air intake goes to the carberator. So, I decided to keep the engine rpms up by holding the air sensor open and spray berrymans carbuerator cleaner in the intake to clean the oil residue in the carbuerator. It cleaned it up, but when I put it back together the engine rpms stay around 1500 and it fluctuates up and down between 1000 and 1500 at idle and the gas mileage has gone from bad to worse...
I'm thinking the o2 sensor is bad and it needs to be replaced... I think the sensor is located on the exhaust manifold end closest to the firewall. The bolts on it look like they could twist off if someone like me get's too rough with it.
I looked at the pictures on the o2 replcaement article in the tech section. I think that is on a later model truck than mine.
If someone has done the replacement on a 91 with the 4 cylinder engine, I'd like to have some coaching here if you would be kind enough to help.
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