I took the air pump belt off my 89 t2 today to figure out if the leaking noise I was hearing was comming from my exhaust or disconnected slpit air pipe (no cats).

now with no belt but all hoses still hooked up to the stock air box my idle is almost full rich at idle. and before it was way lean.

why is this?

 

TOTHETOP

Well i just took my air pump out. I dont have a air/fuel meter so I dont know how mine is..seems to be the same. Maybe it has something to do with the fact that the two lines are still hooked. Kinda a long shot but i figured that might be a problem..crazy **** happens sometimes.,
well at the very least I got you back to the top
later

 

uhhhh... wrong...

Any "fumes" in your exhaust tract is already "burned"..
air pump also pumps the air after the o2 sensor in the exhaust stream...

 

Hey Scott 89tt .......Your car is'nt peculiar. I've been using a digital multimeter to monitor my oxygen sensor directly off the ecu for a couple of weeks now. It had been bothering me that at idle it read .8volts i.e. rich, at idle. During cruise the reading was what you'd expect, jumping from say .2 to .6 to .4 etc but at idle obviously rich at .8volts. Well three days ago I put my acv back on with the air pump and just happen to notice that at idle the meter reads .1 or less. Did not know why. Did not really tie the reinstallation of the acv and pump to it. Just now took my pump belt off and got full rich. Looking at the schematic in the manual I think its the anti-afterburn valve in the acv that at idle is feeding fresh air into the rear port that is causing this phenomenem. Still figuring out if the anti-afterburn should be functioning at idle. Just a thought.

 

scott89tII, I also found out that too, I took the air pump belt and the a/c belt off before I went to the track. Free up some horse's right? but noticed that my A/F gauge(autometer) was showing very rich, when before it would'nt read anything at idle just when I hit the gas, and was cruising. I thought it was the high octane stuff I bought at autozone. Guess not thats why I was hitting high 14's on the GTech w/ belts on. But I could only manage a best of 15 flat at the track. BTW I also have a 89'TII, mabe I'll try adjusting the lean/rich screw that 2 banger mentioned.

 

Before I reinstalled my acv and airpump I did the turn the rich/lean screw thing to no avail. Since reading Scott 89ttii I realize that its the anti afterburn valve which is a part of the acv that is feeding fresh air into the rear port, which in turn is ahead of the oxygen sensor, that results in the lowered reading. The fresh oxygen is leaning out the exaust prior to the oxygen sensor which in turn shows a leaner reading. Doubt very much if there is anything out of whack. I think the same results would have happen on a brand new car if one took the pump or acv off and monitored the oxygen sensor.

 

cool, I thought that it must be from pumping air in making it leaner. I just didn't expect it to move that much.

 

The rich/lean screw by the boost sensor only adjust the mixture at idle. Since the problem was at aidle i guess that makes sense; but just telling those of you that didn't know if you did then o well.
later

 

Scott 89tt....I have to admit that I was surprised how it went from .8 to .1 or less also But again everything I read about oxygen sensors says that they are somewhat inaccurate at lower readings*Autometer.com in their explanation of oxygen sensors*. There is a fellow on this forum who calls himself Irv, Keiths father who in his answers seems to be wired into how the acv and the rest of the solenoids work. I'm thinking of writing him and asking if the anti-afterburn is supposed to be injecting air AT idle. In the description it says that it should inject air into the rear rotor when or during deceleration. And yes, Grey's 10th, I know that the rich/lean screw is effective during idle, but thanks for saying so because frankly I did not know that until I saw that in a post on this site while browsing one fine day.

 

Wrote a post to Irv, Keith's dad. He says it is not the antiafterburn valve that is supplying the air at idle , but the switching valve. The switching valve solenoid is supplying a vaccum at idle to the switching part of the acv and this directs air to the exaust ports, from the air pump. Sorry about the error concerning the anti-afterburn valve at idle.