Kiwi Carguy

I've used the search function and its not what it used to be

I have a 96 993 Varioram here in NZ that is a US spec car. It is fitted with a full Fabspeed exhaust system and Maxflows however it only has 2 of the exhaust sensors fitted with the other 2 tucked away.

So a couple of questions.

The check engine light has come on and I am intending on popping in and getting the codes read. In speaking with the mechanics if the CEL is due to the Fabspeeds and all 4 sensors not being used what is the fix? The mechanics are unsure themselves of a simple solution other than new cats with threads for the sensors.

Also since the cel has come on it has been a little smokey on idle. I appreciate it may be a little hard to say but would this be due to the engine running rich with the CEL on? The tips look a lot sootier although it could be valves aye? Has anyone else experienced this? The car has definitely not been overfilled with oil. The car still runs strong and smells quite fumey/petroly (new words )

I will be taking it to my Indy but just trying to get some ideas before I head on in.

Macca

Best of luck mate!

viperbob

The ECU in a 993 has a learning component (removed from later models). There are certain conditions that if turned off several times will tell the ECU that this condition is normal and will not come back on. I would try this first. I have seen this not work 100% of the time. If after 3 times turning off the CEL with some drive cycles (about 100 miles per cycle) I would just have your shop install some bungs (threaded part weled onto the exhaust to screw in the sensor) after the cat and reattach the sensors.

Kiwi Carguy

Thanks for the advice. To clarify are you suggesting clearing the codes 3 times or resetting the ECU?

Also did you mean you have or have not seen this work 100% of the time. Wasn't too sure if that is a typo?

Does having the threaded bungs installed fix the problem or are you suggesting trying this. I.e: have you done it/seen it done and it worked. Not doubting your info or knowledge as I've been on here long enough to know you know your way around them Just asking for clarity.

Any others experienced this? Have any other suggestions?

Also with a 96 what is the position on ECU chips? Two mates here have had 95's with Steve Wiener chips. Any comments Steve?

Cheers

Nicolas

Hello
Normally you have to put a special shunt to fool the 2nd O2 sensors.
The 1st ones (in front of cat) monitors the A/F ratio when the 2nd ones verify if the cat is in working order.
The DME check the difference in voltage therefore the shunt is a kind of resistor connected in place of the 2nd O2 sensors.
http://www.o2simulator.com/

Steve Weiner-Rennsport Systems

My contribution,.....

1) These cars must have 4 functioning oxysensors to prevent triggering codes related to them. This means 2 pre-cat sensors for mixture feedback control and 2 post-cat sensors for OBD-2 monitoring. If your car has no cats, those secondary sensors must be either positioned to sense clean air, or the circuitry modified to ensure a wide delta in lambda voltages between per & post-cat sensors.

Many '96 cars are a bit touchy as Porsche set the OBD-2 limits a tad too close and corrected that on the later cars. A generic OBD-2 scan tool permits one to reset & clear codes.

2) Good software improves drivability and throttle response on all 993's but the sad news is that the '96 ECU's (.008) cannot be modified. You'll need a '97 ECU (.376) to take advantage of software upgrades.

viperbob

Yes try just clearing the CEL a few times. After you clear it once, it may come back on again in about 100 miles. Try turning it off again. If you do this 3 times, it may just stay off. If it then continues to come back on, then you may want to just install some bungs after the cats and reattach the 02 sensors. Yes if you do this, then the CEL will go off without trying anything else (assuming the cats are working).

OK, also re-read you original post. You have the 02 sensors still attached and your mechanics have not yet checked the code. All of this is irrelevant until you do. Get the code and then we can diagnose. Sorry, I missed the "if" in the sentence "In speaking with the mechanics if the CEL is due to the Fabspeeds and all 4 sensors not being used "

Kiwi Carguy

I took the car into my Indy and they came up with the following codes (and cleared them)

16 Sensor ageing ahead of cat 1-3
17 Sensor ageing behind cat 1-3
22 Sensor ageing ahead of cat 4-6
23 Sensor ageing behind cat 4-6
12 O2 sensor behind cat 1-3
208 SAI system 4-6

The car has no cats and so far the CEL to my knowledge has been reset twice. I'm hoping its not valves but was aware when I got the car that the valves are a weak point and that the US cars have SAI issues.

The tech run the car through some rev ranges and short bursts on the throttle and no smoke. So far in 150km's of driving no smoke since?

Also what would be a fair price to pay for a 97 ECU?

Seeing as I have no emissions testing here in NZ could the SAI system be removed and what is involved in that?

Lastly I live a good hour from our Indy and was considering purchasing a OBDII reader. There is not much available here in NZ. Is this a good one to consider? http://www.trademe.co.nz/Trade-Me-Mo...-216505560.htm

Thanks guys for all your assistance so far

The plus side is the tech said the car sounded great

KCG

Kiwi Carguy

O.k so the CEL came on again and the fault was O2 sensors again. I am looking at buying one of these simulators to cure the problem.

http://cgi.ebay.com.au/Universal-O2-...3A1%7C294%3A50

Silly question... do I need one or two as I know there are two sensors plumbed in? I'm guessing one simulator?

Also the guy selling them has two types listed. V1 and V2 which has a heater component? Any idea which one for a 993. Again I'm guessing V1?

TIA