chs9

Hi all,

I've been trying to chase down a code 71 issue on a federal 1994 Toyota Pickup, 4wd, 22re. My gas mileage has been variable since putting in a rebuilt engine, but has recently been as low as 10 MPG's. Sometimes it's as high as 22, but it's been awhile since I've seen that.

In testing out the components of the EGR system, I found that the EGR vacuum modulator (port Q) was not drawing vacuum at ~3500 RPM's. Unfortunately, it turns out the throttle body is not drawing vacuum at the R and E labelled vacuum ports at 3500 RPM either.

The FSM I have covers all of the test up to this point. If the throttle body is not pulling vacuum, what are the potential causes? potentially the TPS? Other suggestions?

scope103

The TPS is just a sensor; it has no effect on vacuum to the ports.

The ports just enter the throttle body at certain points in the travel of the throttle plate, so that the throttle plate uncovers them at the right time. If you're getting no vacuum at all, it is almost certainly due to a clogged port.

I'd start with carb cleaner shot through one of the little straws they come with. You could try clearing the passage with a wire, but be very careful. The passage isn't very large, and it isn't a straight line, so a wire might not work at all.

chs9

Great, thank you for that explanation Scope.