'89 Tercel Weber Carb Swap - EBCV?

[noahthefrog]

I recently replaced the stock carb on my '89 Tercel with a Weber 32/36. Most of the time it runs well, but when it get's hot outside it lacks power and stumbles some when accelerating or going up steep hills. I found that adjusting the fuel/air mixture to a leaner mix solves it, but makes the car run rich when it's cooler outside. If I set the mix between the good-for-hot and good-for-cool weather settings, the car runs poorly in all conditions. The car is also going through gas much faster than it did before the summer heat kicked in.

So I am wondering if I hook up the Electronic Bleed Control Valve from the original carb, will the computer use it adjust the fuel/air mix on the fly? Do I need to hook up anything else from the old carb to force the computer to go into closed-loop operation? Anyone tried this before? Any other ideas to achieve the same result?

[96paseo]

Just came across this article. Has some really good troubleshooting ideas.
http://www.underhoodservice.com/Arti...ftermarke.aspx

[noahthefrog]

Originally Posted by 96paseo

Just came across this article. Has some really good troubleshooting ideas.
http://www.underhoodservice.com/Arti...ftermarke.aspx

Thanks for that very informative link.

I've already tried connecting the EBCV and it seems to have no effect. Sounds like I should set the mixture screw to run rich like the original carb would've been tuned and if it doesn't run rich, the ebcv is doing something. I will try that next.

All I really need is for something to read the 02 sensor and adjust the fuel/air mix w/ the EBCV accordingly. If I can't get the ECU to do it, I'll have to build the circuit or manual control myself. I've been considering getting a variable resistor (volume knob) and hooking it between the EBCV and 12v battery power for testing purposes, but I'm afraid I might fry it! Which brings me to the next question - Does the amount of air bleed scale with voltage or does it adjust it based on some other signaling method?

[noahthefrog]

Never mind the last question

I adjusted the fuel/air mix to be richer and sure enough the EBCV kicks in to lean out the mix when RPMS increase above idle. Apparently nothing else electrical from the old carb has to be connected other than the EBCV, vacuum switch, and of course the O2 sensor. I love the simplicity of this car (well, once the stock carb is gone at least)! Will find out whether it helps the performance once rush hour is over.

EDIT: Test drove it and the car is faster and runs smoother than it ever has! Time will tell if it helps the MPG, but I can't see how it wouldn't.

EDIT: Found this very useful in understanding the 87-90 Tercel stock carb fuel/air mix system. Might be useful for anyone else having to diagnose or re-engineer this system: http://repairnet.aircare.ca/document...yotatercel.pdf