When TP or Datamaster talks about the AIR divert enable temp, where is it getting diverted from and to?

I've done the searches, read the stickie, but no where can I determine for sure where it is getting diverted from or to where.

Since the AIR is supposed to be going to the exhaust manifolds at startup (cold loop) from what I've read, I'm assuming this means the temp it starts going to the cats. However I've read in this forum how under certain conditions it gets diverted to the atmosphere. So "divert" seems to have multiple uses.

Since I've gotten "bit" by assumptions before, can someone who actually knows clear up the confusion on this for me?

I've tried testing on my own car (91, S/D, $8D, 730), but I don't ever seem to be getting air going to the manifolds at all. And I've tested it with two different divert solenoids. So I'm trying to find out what is supposed to happen and when.


- Vern

 

What I get from the notes and looking through the $8D commented code, if the temp is below the value at L839A the air gets diverted downstream (not to manifolds). Above that temp it goes between manifold and downstream based on loop status, load, and rpm.

 

Bunch of air pump info in this thread:

https://www.thirdgen.org/techbb2/sho...Helm+%2Bdivert

RBob.

 

Well, I've read the referred to post, as well as the linked post inside it, and been doing some thinking - what a bunch to absorb! My head hurts.....

I got started into this whole topic because something doesn't seem quite right with my 383 set up in my 91 Firebird. I was getting richer than normal WB O2 readings (which is on the right side of the motor) when the NB sensor on the left side was being used to keep everything stoich.

I've pulled the hoses off the diverter valve and started up a cold motor to see if the valve was any good. I never seem to get anything coming out of the atmosphere or exhaust ports hoses. Picked up another (used) diverter valve, and get the same symptoms. Air never goes to the ports. So I set the 101mV O2 offset to 0mV and low and behold, what the ECM is now adjusting everything to is pretty darn close to 14.7 according to the wideband while cruising. But I'm not so sure that was the smart thing to do. I could completely disable it with the 14.75 to 151 enable temp setting, but I was trying to stay emissions legal. I wanted to let the cats keep doing their "work" if you will (and hopefully not burn them out and have to replace them after only a years usage at the next emissions test). My initial thinking was just let the air always go to the cats and don't worry about it.

Now I'm trying to learn more about how it all operates, and why (where possible). I'm still a little confused on when and how that 100mV offset is used. According to Trax's (and others') posts, whenever air is "diverted" the ECM changes the O2 threshhold values by subtracting out the 100mV. This almost sounds like "diverted" means anywhere other than the ports, and that $8D assumes initially that the extra air is being injected to the ports. Then when the ECM decides to send this extra air elsewhere, it subtracts the 100mV since the extra air isn't there. So, are the O2 threshold values assuming air is going to the ports? Sounds like it if I'm understanding all this correctly.

I've read that if you eliminate the air system entirely, you need to reduce this 100mV offset to zero. I don't want to eliminate the AIR system. But what would the proper way be to force it to always divert to the cats? (At least until I can figure out how to tell if it is energizing the ports solenoid when the ECM thinks it is) And would this cause abnormal CO readings if I do this?

Since I've tried 2 diverter valves with no success, it would be awfully coincidental that both had a bad ports solenoid even though they are used valves. I also find it hard to swallow a $275 price for a new one just to find out the same problem exists.

Besides all the questions, does anyone have any suggestions? Or ideas on how to further diagnose the diverter valve?

 

Have you manually activated the solenoids to see if they change air flow? From what you are saying it sounds like it is being commanded to change position but it is not happening. You could stick a voltmeter on the circuit and verify that the circuit is being grounded when the ecm commands it to be.

 

Thanks, Eirc - that's a good idea to try.

Question --- if I ground the wire manually, shouldn't it force the solenoid to energize? Would this hurt anything wiring or ECM wise to try?

Thanks for thr replies, guys!!!!



- Vern

 

I would isolate it completely and use jumper wires directly to a 12 volt source and ground. If they do switch air flow manually then I would look to see if it is being grounded at the solenoid when commanded.

 

Sounds like an even better plan, Thanks! Should have some results to post tomorrow (or late tonight).....