Hey all i am struggling with my 1989 3vze mt that smells terrible under load. Its a rotten egg/sulfurs smell. I recently tried changing the o2 sensor with Denso 234-4152, which is the pn listed for my truck. I have read that there is sometimes an alternate part for California trucks, but i assume that is for the later dual o2 equipped trucks.

I've already confrimed the timing at 10 deg btc, tested the distributor with the fsm. tested the vafm following the fsm, replaced the tps which was very bad. I've noticed it is corroding distributor caps and rotors quickly.

The truck passes Cali smog, but also has a brand new cat, and based on the stink it wont last much longer. It runs very well for a 3.0 at low speed, but when its under load going up a hill or pulling onto the freeway it stinks.

My next step is to hook up an analog volt gauge to the VF1 see how it swings rich and lean under what conditions.

https://people.well.com/user/mosk/Vfsignal.htm Might make this a permanent gauge on the dash.

Thoughts guys?

 

Examination of what the upstream O2 sensor is saying is a good idea.

Another good idea is to use an IR gun to determine the cat temperature under different conditions.

I'm not sure that the exhaust stink is necessarily indicative of impending cat destruction.

You make no mention of poor fuel mileage.

 

So reporting back, the needle swings at around 2.5v but never as high as 3.7. It idles at about 0.12v (throttle closed so not giving a reading) and its only when i really get on it that it stinks. I am noticing that this is when the needle drops again to the 0.12v. So i am assuming it is going open loop before i hit WOT? Is this normal?

Other than that its street manners seem ok, It has been sitting for some time so i don't have a good number of mpg.

 

Tested fuel pressure today, 45 static engine off. 46 running vacuum disconnected. 40 idling. Seems like everything is fine and ill caulk the high side error up to the rental gauge. If it smelled idling i might consider replacing the regulator, but my problem is only engine under high vacuum. Once the fuel fumes air out ill test it with the diagnostic mode jumper in place.

Does anyone know if you can hook one of these:
https://www.summitracing.com/parts/sum-g2986-1
to the OX port on the diagnostic port? Still considering something to have up in the cab to see what is going on.

 

So forgive the triple post here but i am trying to understand how to read this/the VF signal logic. So when i was doing my initial testing i was driving around with an analog voltmeter hooked to VF and E1 and watched as it for the most part hovered at 2.5v with some small variation, (perhaps my meter just doesn't respond quickly.) When i would idle it would drop to pretty much zero which i assume is open loop. When i would accelerate hard, but not WOT it would do the same. Is this normal?

Now i am trying to understand the other modes here with the T and E1 connected. If i am understanding this it will give me a binary 0v or 5v value just to indicate that there is a problem if the engine is off, and running it will bounce hopefully more than 8 times in 10 sec running at 2500 rpm.
Correct?