mpgs

[joe_peters]

I've heard people say that the cracked exhaust manifold kills the mileage is that because of the leak or because it messes with the O2 sensor?

1. Leak upstream of o2 sensor, sensor reads lean, ECU/PCM enrichens mixture.

2. Leak in exhaust reduces backpressure, poor scavenging of exhaust, lowers power due to contaminated mixture during intake stroke.

3. Heat from exhaust leak effects sensors, changes sensor readings to ECU/PCM, poor operation from false inputs.

4. Heat from exhaust leak increases fuel charge temperature in intake, rise in intake temperature reduces air/fuel misting and reduces effective burn.

Probably some other things I'm not thinking of right now, but it is late.

 

[lawsoncl]

I normally get 18 mpg hwy on my 89 MJ. I'm lifted with 4.11 gears, 32s, and 225k miles. It got a solid 21mpg when I bought it used before I lifted and regeared! It recently dropped to 13 mpg over a period of two months, which I corrected by replacing the O2 sensor. A bad O2 sensor on the Renix doesn't seem to trigger any other indications other than really crappy mileage and poor low power. It was obviously bad as it rattled when I removed it.

So for the guys setting really crappy mileage, perhaps its a bad O2 sensor.

 

[projectTK]

i get 12mpg in my 89 cherokee with 87 corvette 350

Got a bad oxy sensor i used to get 15mpgs

 

[joe_peters]

i get 12mpg in my 89 cherokee with 87 corvette 350

Got a bad oxy sensor i used to get 15mpgs

NOW that makes me jealous!!