Try bumping the timing a little. What brand parts did you use?

 

Parts Brand

I used the Bosch Universal O2 sensors due to availability. Plugs are iriduim NGK and wires are MSD. CAT is Magnaflow.

 

Bosch O2 sensors are notoriously problematic with these trucks. Might wanna try Denso sensors from Amazon.com, cheapest I found them. Get the part numbers from your dealer. Your not running Magnaflows high flow Cat are you?

 

what is the coolant temperature? if it is running on the cool side, say 160-170degF it could keep it running rich.
also, if the coolant temp sensor is out of spec or there is excessive resistance on that circuit it could make the ECM "think" it is still warming up.

A leaking cold start injector will fatten it up, as will too much fuel pressure (not very likely but worth checking)

I've seen some other models with leaking fuel pressure regulator diaphrams.

If the VF voltage in the diagnostic connector is greater than 2.5V then it means the ECM is adding extra fuel because it thinks it is lean(incorrect O2 readings) this can be caused by faulty O2sensor, a issue on that circuit, or by an exhaust leak that allows some air to enter the exhaust upstream of the O2 sensor. Air can also get in because of a problem with the pulse air system.

If the VF voltage is lower than 2.5V (like down around 0.5V) it is trying in vain to pull the mixture back. more likey a mechanical or adjustment issue.

Hope this helps...

 

you have the wrong smog tech !!!!:chug:

 

If i can't find anything wrong, I will replace the Bosch O2 sensors and advance the timing a little. My CAT is a direct fit from Magnaflow but it doesn't say High flow (#39884).

I measured the VF terminal at >2.5v during warm up and after warm up 2.25v.
I measured the O2 terminal at .2-.8v during warm up and .1-1.0v after warm up.

I don't know how to check to see if the coolant temp sensor is within spec nor if the cold start injector is leaking. I will be looking into those items as well as the fuel pressure regulator.

As for the wrong smog tech, he is just hooking it up to a machine and not charging me until it passes. But yes, he doesn't seem to be a mechanic what-so-ever.

If I can't figure it out, I might be forced to go to another smog station that also repairs vehicles...

 

To check the coolant temp sensor, reference the toyota FSM.

Google for one from 1993, can't link it for legal reasons..

 

with those readings on the VF, I would not expect to find a problem with the coolant temp sensor. However, you can check the voltage across it while it is plugged in with the engine fully warmed up and expect to see between 0.6V and 0.8V. really if it is less than 1.0V the ECM will think it is warmed up all the way.

the O2 sensor could be biased and just not keeping it where it should, But I wouldn't expect that either.

The readings you have may be a weak cat, or even unequal fuel distribution. If your injectors are gummed up, a couple cylinders may be getting partial misfires causing the exhaust O2 to go up and then the ECM corrects by adding more fuel. I'd suggest running some good cleaner through it and making sure the CAT is good and hot before the test. This is where your "better SMOG tech" comes in to play.

Hope this helps.

 

Checked the Coolant temp sensor, 2.7 cold and .39 warm. Checks out ok according to the FSM (pg EG1-209)

Checked the cold start injector, doesn't seem to be leaking--3 ohms which is within specs according to FSM.

After reading a little online and the FSM for fuel issues, it was recommended to check the VSV. All at 36 ohms which is within specs according to FSM.

Checked O2 sensor according to FSM (pg EG1-212), functionality tested normal (according to flow chart in FSM). O2 sensor cold has 5.9 ohms, within specs of FSM.

My next chance to take to smog tech will be next Thursday. I will be running the truck a little this weekend with good injector cleaner mixed in with some high octane fuel. On Thursday, I will bring it in after driving a little (getting the CAT good and hot). I advanced the timing a little, currently sitting at 8-10 degrees BTDC.

Hopefully it all works out this time...:headbang: