to check for leaks, the easiest way is to get a propane bottle or acetelene with a torch. Don't light it, but with the gas open, run it around the intake. When (or if) the engine surges, you've found your leak.

 

i have a question when you fix this problem how many more mpg do you get out of it?

 

Sorry, but I cannot honestly say.

I replaced my plenum gasket, heads, muffler,catalytic converter, o2 sensor, and did some of the standard mods like TPS, thermostat, and intake pretty much all at once so it wouldnt be a fair measurement.

IF its leaking I would change it and not worry about mpg's, I diagnosed mine too late, thats why I had to replace everything. The o2 sensor will go first, then it will plug up the cat, which will create excessive heat in your exhaust, which will eventually make your heads crack since they are prone to do that anyway.

Good luck, hope that helps, and if you are doing JUST the plenum gasket its not that hard and could get done in a few well prepared hours.

 

none. i don't think it has any effect on mpg. when its leaking its sucking air and oil and running lean and hot. maybe pinging. low on power, but its not really using any extra gas.

 

Wouldnt it running low on power effectively cause you to use more gas?