mezarx7

running real rich just adjusted timing but my engine light turns on/off. off when giving it throttle, on when releasing throttle, any suggestions..

RotaryRocket88

iTrader: (7)

If you failed smog, you most likely just need a new cat. A working air pump and ACV are also going to be critical.

How are you adjusting timing? There is no need to do anything unless someone has been playing with the CAS. The ECU advances timing above ~1000 RPM, so you will only see the pin line up with the marks on the pulley when the engine is idling below that level.

mezarx7

thanks i'll check out the acv and the pump seems to be working and then i guess the cat.. thanks i'll let you know the verdict

mezarx7

how do i check to see if the acv is bad?

RotaryRocket88

iTrader: (7)

You should verify that the vacuum lines are hooked up correctly, and you can test the relief and switching valves/solenoids. There are tests in the FSM.

calpatriot

Smog: check these three things...
1. Check for closed loop operation (O2 & ECU cycling rich lean 8x in 10 sec at cruise). Check with a single LED checker at the test connector. See my posts on the 'green lamp'. Note: if you fail to do this, you may pass smog with a new cat, but the rich mixture will cause you to destroy the cat, and need a new one at every smog check.
2. Check to see that the ACV is working. Quick and dirty check is to reach under the right front fender at idle. The relief air comes out of a rubber elbow, pointed in towards the center of the car. A very light breeze out of the relief tube is ok. Strong wind there means trouble with the ACV, and no port air=failed smog check.
3. Bang on the cat with a rubber mallet, or your fist. If you hear little stuff rattling around inside, have the cat replaced.

If you replace the cat, run the car for a 100 miles or more to 'run in' the cat before doing to smog check. Do the check with the car at full operating temp, and turn off the AC, fan, and any other extra stuff you might have running.

mezarx7

so what if there is strong air coming out of the elbow form the acv. what then need new?

RotaryRocket88

iTrader: (7)

If there is a lot of air coming out of the silencer tube under 3500 RPM, the relief valve in the ACV is open. Check the relief solenoid and related vacuum lines.

calpatriot

Maybe...maybe not. I just went thru this drill.

You will need a voltmeter, and a vacuum test pump (i.e. Mityvac).

There are two critical valves in the ACV, at least as far as the smog check is concerned; the relief valve, and the switching valve. Both need to be activated (vacuum applied) in order for you to get port air, which is necessary for a successful smog test.

On my S4, there are two 4mm vacuum lines that join the LIM on rhe center right side, right at the boundary to the UIM. The front one runs the switching valve, and the back one runs the relief valve.

If you pull the rear line and check it for vacuum (hook the vac gauge up to it). You should see about 15" vac at idle. If it is not there, trace the system upstream and find out why.

Try putting the mityvac on the nipple, and pump up 20" of vacuum. If the volume of air coming out of the relief tube decreases to about 10% or less, the valve is working ok.

If not, you can pull it and check it on the bench.

If the probelm is upstream, look for misrouted vac lines, inoperative solenoid valve (its the front one on the left side of the engine), miswired solenoid valve, no vacuum coming from the upstream side of the valve.

In my case it was the latter; there was no vacuum at the nipple on the intake plenum. The relevant nipple is one of three on the front side of the plenum, above and behind the alternator (S4, NA). It is the center of the three.

I ran a new vacuum line from an unused nipple on the back side of the engine--viola, smog check passed.

mezarx7

thanks for the imput guys i'll check these out and hopefully it'll be an easy one thanks