I own a 1988 10th Anv. Turbo II with a modified Greddy intake and intercooler.
No trouble passing smog until recently when it jumped from barely measureable to 5x limit.
No mechanic will touch it and one mentioned that some possible causes might be the ACV and the mixture sensor. I know how to check the ACV, but don't even know where the mixture sensor is or how to check it.
Any help would be greatly appreciated.

(Any more ideas on what might be an issue would also be appreciated. The car also has a bad habbit of back-firing)

Thanks.

 

what is it failing HC,CO,NO? and what are the numbers.. any other mods.. this info would be a big help

 

15 mph, 1815 RPM:
HC is failing with 572 ppm
NO is failing with 2009 ppm
CO passes with .71%

25 mph, 2034 RPM:
HC is failing with 461 ppm
NO is failing with 1676 ppm
CO is failing with .78%

Intake mods consist of a K&N FilterCharger kit, Greddy Inter-Cooler Kit, Greddy Blow-Off Valve, and Fuel Cut-Off defeater (which is disabled at the moment)
Exhaust mods consits of a Racing Beat 3" Cat-Back kit, but also included is a custom down- pipe and custom removable CAT.
I have replaced the BAC in recent years and I have checked all the rubber intake components for holes. I also have had the EGR repacked in the last few years. It doesn't sound like I have a vacuum leak anywhere.

Thank you for your help.

 

Checkout the ACV per the FSM.

 

You will have to excuse my lack of knowledge of acronyms...
What is FSM?

 

F.actory S.hop M.anual. Here ya go. http://www.teamfc3s.org/main/factory...TEMS_TURBO.pdf
and good luck. Hope it's nothing too costly. BTW, Have you ever replaced your Catalytic converter? Might have burned out by now.

Question though, How the heck do you repack an EGR? Isn't it just a valve that's controlled via a diaphragm? or did you mean replace?

 

The "mixture sensor" is the O2 sensor. There's no easy to check it. Just replace since they are about $30 at an auto parts store. All you need is a generic one wire sensor.

The cause of your failure sounds to be related to the ACV valve since you mention a backfire. As mentioned, the Factory Service Manual has instructions on how to test it.

In addition, it is likely that the car is out of tune. A full tuneup will do wonders.

 

The EGR had a new diaphragm installed, thats what I meant by repacked.
Also, is there an easy way of determining if my CAT does indeed need replacing? Is there any kind of visual inspection?

Thanks.

 

If your ACV is the original one, and it's a turbo one, I guarantee the diaphrams inside are rock hard and are not working. Been there, seen that. It's hard to come by a used turbo ACV that has good diaphrams. See the Fuel section of the FSM for checking it out.

 

Also, is there a way that I can test the ACV off my car? I removed it to visually check the vacuum hoses and such. With the intercooler pipes in the way, the method descirbed in the manual to test is going to be very difficult once reinstalled.

 

Get a piece of vacuum hose. Put it on the very bottom small pipe. The one attached to the mushroom looking device at the bottom of the ACV.

That nipple usually, on a Turboii gets airpressure to operate. So blow into it and see if the valve inside the LARGE nipple at the bottom will move as you blow. OR you can suck on that small nipple and it should hold a vacuum indicating the diaphram is good. Not holding a vacuum means the diaphram is kaput.

Then there is a nipple on top that sticks straight UP. Put a vacuum hose on it and suck. It MUST hold a vacuum. If not, the diaphram is busted and the thing isn't goind to work at all.

The above determines if the diaphrams are good or not. It does not determine if the signals to the acv are good/bad. The signals come to the acv from the Blue Relief valve in the form of pressure to the bottom of the acv and from the Grey Switching solenoid in the form of vacuum to the top nipple that sticks straight up.

The solenoids on the acv do little to nothing for passing emissions. The Split air solenoid only comes on if fifth gear. The Port Air solenoid comes and goes with acceleration/deceleration. That one can be over come by removing the solenoid and removing it's poppet valve and reinstalling the body of the solenoid. That act will add a Small amount of air to the exaust ports in addition to the air that should be going there anyway.

I think a person could take a look at the large one inch nipple at the bottom of the acv. Then think about it. If that hole was blocked up, then all the airpump air would have to go to the exaust ports and or to the spit air pipe. Just a thought.

If you took that route, then make sure you remove the switching diaphram and valve. You remove the four small screws and the diaphram and valve pull right out. I've never disabled one but suspecty you can remove the poppet valve and reinstall the cover and four screws. That should leave a wide open passage to the checkvalve and then on to the exaust ports. The checkvalve should be retained. Just clean the carbon off and make sure you reinstall that checkvalve. I put up some jpgs on that other forum called FC3S whatever forum. I put them on the TURBO part of that forum about two or three weeks ago. Forgot the thread name but had something to do with emissions. It's a slow fourm so the thread ought to be on the first three pages .

Your converter could be marginal though and causing some of your problems. IF say you blocked that LARGE nipple and tried the emissions station once again and did not pass..............I'd go buy a cheap catalytic converter from CATCO or some such place and you'll pass in a heartbeat next time.

EGR'S have little to nothing to do with passing. I've not used one in years. S5 don't even have one, so don't spend a moment on that egr or money on one.

 

This link has some jpgs http://forum.teamfc3s.org/showthread...hlight=HAILERS

 

This is awesome info, thanks a lot.
I already replaced the Oxygen sensor and I checked the ACV like you suggested and everying checks out.
I will run the car later and see if anything has changed, if not...
tomorrow I guess I will start looking for a good muffler shop etc. to see about getting the CAT examined/replaced.
Any other ideas would be great.
Thanks.