Got a 3000 GT/SL that is running too rich and can't pass emmissions. Is the fuel mixture on these cars adjustable? I have the gas analyzer, but dont know if these cars can be adjusted.

 

If your car is running rich there is probably something not right with the car... but as far as controlling the fuel I know the S-afc and other elec. things you can buy can control it. But not really sure if thats something u'd be lookin for... mainly used for performance tuning.

 

On the stock ECU, NO, you cannot change a/f ratios. Like evil said, with an aftermarket piggyback or standalone ECU you would be able to adjust that.

If you are running to rich, you might want to check out some basic things like plugs and wires, O2 sensor, hell even your air filter.

 

Yeah, the programmable approach would be the preferred method for a TT car perhaps or for the autocross enthusist, but its just a cool daily driver and I think installing those mods will really just be covering a problem that needs to be corrected. Obviously the car passed emmissions when it was new, so it should be able to pass emmissions without the help of the ADDITIONAL 'guru' electronics. If it's not meant to be adjusted then if eerything is right it should pass. I guess what I am looking for is perhaps suggestions on the most common causes with these cars that will make them run rich...or missssfire; that is what the gas analyzer/emmissions test is showing me. Too much unburned fuel is being exhausted.

On the recommendation you offer to give the car a tune up, it's just had a complete one including all OEM parts: $12 NGK plugs, air&oil&fuel filters, O2 sensor, synthetic oil, etc. Have confirmed the throttle position switch functions correctly, the coils at least ohm correctly, the catalytic converter was replaced. Have also taken some voltage readings at the main ECU connector and so far they are all spot on acording to the OEM maintenance electrical troubleshooting docs. ECU shows no fault codes after being reset and driven a number of times but it was purchased with a fault '62' which indicates the variable intake sensor and stepper motor were gone, this has also been replaced (got to buy the ENTIRE manifold from the dealer to get the sensor!).

The only 'sympton' I have and it may not even be related to the emmissions problem is that the car has poor cold engine drivability. It seems to be low on power perhaps even kinda skip a bit at half throttle till it warms up...that takes about 2-3 minutes. Then it seems to run quite well. It's a strange problem, never had one do this, when it's cold it acts as described above and sometimes it's like a turbo kicks in and the car races forward...zoom.

The only true 'problem' I have been able to find is inside the air mass meter. This deice contains a thermistor. It ranges from 400 Ohms to 6K Ohms depending on the temp of the air passing through its collector. At 32F it should read 6K and the highest I can get is 4.7K, and at 180F it should be 400 and I can only get 600Ohms. At 68F it should read 2.7K Im getting 1.7K. So according to the electrical guide it's wrong, but I had a 92 TT that has the same air mass on it with exactly the same readings and it runs wonderfully...So Im not convinced it should be replaced, especially since its not throwing any fault codes.

Thats my story and Im sticking to it.

ANY common problems that might cause these things? I pray to the #GT Gods to bring me either the chance to find it or a guru appear and help me find it. Better to have more than one mind looking at it, Im sure its here somewhere.

Thanks all

 

Also thought just now that I could easily put a variable resistor into the airmass meter to determine if adjusting the resistance range of the thermistor up or down to the factory setting for either extreem should produce a change in the emmissions....but only if it were a 'problem'. It would be nice to have the luxury of a well stocked parts bin and a goods parts manager.

 

I dunno man. You might want to check out 3si.org or US3S.com. Most those guys eat, sleep and breath the 3S platform. They may be able to point you in the right direction.

I do know that these cars do run rich from the the factory. Have you check the IAC (idle air controller), that may be causing some of your cold running problems.

Good luck.