Scan tools for pre OBD2 toyotas

[Jeremy-WI]

Are there any avialable at a decent price? My 91 is driving me crazy with gas mileage dropping. New fuel and air filters, O2 sensor, distributor cap, rotor, wires and plugs, thermostat and temp sensor(not the one for the gauge. I wish I would have kept the old dist cap around(130K on it) to see if that would straighten it back out.

[natenelsen]

by the way a '91 will be obd1, and the only scanner I have used for mine is a snapon, sorry not much help there. Sounds like you covered most of it, what is your gas milage like now and how has it gotten worse a steady decline or all at once? have you put on a lift or bigger tires anything like that? Is your truck 4x4? Did you put on a factory O2 or just a universal from AZ? Did this drop happen before or after the tune-up? The more you can share the better.

Nate

[natenelsen]

oops, sorry I misread you post heading and missed the *pre* part of the obd2 sorry, I guess I should look before I leap.

Nate

[Jeremy-WI]

It has dropped from 30 mpg to 26 mpg in a couple years, and that was before my new exhaust and Bosch O2 sensor(Bosch work well on my 96 Chevy). No 4 wheel or lift, same size tires as factory. Picked up a piece so I can hook my fuel pressure tester up to it. Is the pressure supposed to hold steady on these, I can't even hear the pump run but the truck runs decent. The timing is at 5 degrees(never had to adjust). It would be a lot easier to figure out if my Autoxray would hook up to it. I remember having 3000 miles on an oil change and getting 33 mpg and if it keeps this pace up it will be cheaper to drive my V8 4x4(19 mpg)

[natenelsen]

Break out the multimeter and see what your avg reading is at your O2 sensor, it ought to be around 500mv or so.

It sounds like everything is okay with the ignition, I would look at the fuel next, I would clean the intake runners, idle passages, and the backside of the intake valves, in addition I would pull the injectors and take a look at what kind of spray pattern they have. I will bet you have a leaky and/or dirty injector(s). Just be prepared to replace the o-rings, the insulators, and the grommets on the injectors when you do this, you can only get the grommets from a dealer and the insulators that are aftermarket leave a little to be desired, all told it cost 50$ for less than a handfull of rubber bits, ouch.

Oh when you get the grommets from the dealer you will think that they gave you the wrong bits, but no, the ones that have been in a long time get very deformed and look nothing like they do when new.

Nate

[natenelsen]

darn did it again and hit the post button too soon. Be sure that your multimeter is rated to work on cars it should be at least 10megaohm input impedance, that way there is no chance that you damage the pcm while using the meter. I have never seen a meter advertised as a AUTOMOTIVE meter that did not meet this standard.

Thought I might better include that little tidbit

Let us know how things are comming

Nate

[Jeremy-WI]

I plugged the vacuum line to the egr, mileage seems to be better but I'm only going by the gauge for now, only been 40 some miles. I should have a better idea on thursday. Gonna check out the filter on the vacuum modulator now. Thanks for the ideas

[Jeremy-WI]

Its back up to 30 mph now, dumped in some engine flush before I did an oil change and it even seems to have better power. I am thinking a sticking valve must have caused the problem. The egr experiment had no mileage improvement. I checked the air presssure in tires, was at 24 and I raised it up to 34 psi and no improvement