old4runner

My '89 has been idling rough and had bad (11mpg) mileage a lot of what I was reading in this forum suggested that I probably had TPS adjustment. After checking and rechecking my tps I finally decided that TPS just wasn't it. I finally figured out (with starting fluid and a rag) that the issue was a vaccuum leak at the cold start injector, once I fixed the vacuum leak my mileage jumped 5 mpg and the idle is as steady as can be, but a little high. Anyway I thought I would contribute this post hoping that maybe I would help some poor guy who is fighting a similar problem and is likewise reading a lot of old threads that suggest his TPS is out of adjustment.

dktool

I too am experiencing piss poor mileage and my tps has been checked and adjusted per the manual.

If the ox-sensor is bad, will it cause issues WITHOUT throwing a code or check engine light ?

The truck starts and runs great but the tailpipe is black and the mpg is around 11

It recently passed a smog check with ease and the readings were no were near the hi limit on any of them.

Any thoughts or do these 3.0 / auto combinations just SUCK ?

dktool

anyone ?

TNRabbit

Dang, dude; chill! People work around here~

Poor fuel economy can be MANY things, including:

-Vacuum leak (most common)

-O2 sensor (doesn't usually give check engine light)

-Cold Start Timing Switch (tells the engine it's warm)

-Leaking cold start fuel injector

-E-brake sticking

-There's a sensor inside the TB that coolant passes through; if block or otherwise faulty, it can make the ECU believe the engine is cold & cause it to run very rich.

There are others I'm sure, but that's all I can think of at the moment.

dktool

Does the cold start timing switch only tell the ecu to keep firing the cold start injector until it reaches a certain coolant temp or does it put the ecu into open loop and screw up feedback from other sensors ?

I have no vacuum leaks

The e-brake is not dragging

The ox sensor in an unknown at this point

Timing is correct

Does a 91' TB have the coolant sensor you mentioned ?
The only electrical connection on mine is for the TPS.