poor gas mileage

[viali8]

i have had a gas mileage problem for some time now. i have an 87 325 and am getting 21 mpg on the highway. here is a list of the things i changed. fuel filter, plugs, air filter, fpr, coolant temp. sensor, and O2 sensor. the last thing i changed was the throttle postion switch. i did not buy a brand new one but used one from a junkyard. My question is, do i not to install the TPS in a specific position to function properly? thanks Matt

[ivo316]

Check your 02 senstor with a tester, sometimes they are faulty when new.

Check (this might sound dumb) your brakes, they might be dragging

Check all your vacuum hoses for cracks or sloppy fit.

Cylinder Compression test. (worn or broken comprssion rings)

Hook a vacuum meter to your intake manifold, the reading will tell you if you have a burnt/damaged valve.

[jlevie]

The TPS and idle stop have to be correctly adjusted. That's done by disconnecting the ICV and adjusting the throttle stop for an idle of 850-950rpm. Then the TPS is adjusted so that the idle switch closes when there's .020-040 clearance between the idle stop and the throttle arm.

[redhatpat]

The TPS and idle stop have to be correctly adjusted. That's done by disconnecting the ICV and adjusting the throttle stop for an idle of 850-950rpm. Then the TPS is adjusted so that the idle switch closes when there's .020-040 clearance between the idle stop and the throttle arm.

That's a pretty high idle rpm. You sure about that?

[jlevie]

I can double check the Bentley tonight, but I'm pretty sure that's correct. With the idle stop and TPS correctly adjusted the DME will regulate idle speed via the ICV.