348: "Lambda Regulation" error code--What does this mean?

Lambda regulation is the mixture fine tuning the lambda sensor (O2 sensor) is used for. It just keeps the miture at optimal (about 14;.7 fuel/air mixture) at low power, maybe 20% throttle. If it is not working, the engine will run richer than it should. With no cats on the car to overheat, that probably only means reduced fuel milage, although it might cause the plugs to soot up. Why the code for regulation and not the sensor is on I don't know....

 

Dave -- One (relatively easy) thing you might try is measuring the voltage between the outer case of the offending O2 sensor and the "ground" that the injection system is using (should be low -- like less than 0.1 VDC) during warm idle.

The signal from the (single) O2 sensor active lead (measured relative to ground) should be a slow sinusoid (period of 1~2 sec) going between 0 VDC (ground) and +1 VDC during warm idle. I know you probably won't have an oscilloscope, but if you just measure it with a voltmeter you should see the reported value banging around between 0 to +1 VDC during warm idle (e.g., if it's pinned at a constant value during warm idle you'll know that something's wacky with either the actual fuel delivery or the O2 sensor itself).

Since you have one side not reporting this problem, you can make the same measurements on that side to see if they are similar or not.

Just some suggestions...

 

It means that the O2 sensor is operating out of parameters. It is trying too hard to either lean or enrichen the mixture to achieve a proper fuel mixture. It can be caused by a cyl miss, vacuum leak bad injector, you name it. It is usually a symptom of an underlying problem. Any time you are driving at a relatively steady state the O2 has authority for fuel mixture so it's proper operation is important. It can cause poor emissions, poor fuel mileage and loss of power. The underlying cause can cause who knows what. The boys in the white lab coats who designed that system had no idea of the wide variety of circumstances a car would be exposed to out in the real world so it is a common problem on early Motronic 2.7, so much so that many people just ignore it. That is OK as long as you be sure that there is not a serious problem causing it.

 

Well I wouldn't drive it until you get the problem fixxed. The reason being that if you are running rich you can burn out the cats fast. Before you go changing parts out, have a look at the clip on connectors. There is a rubber boot that covers the back of the connector. Pull that back and then check the condition of the wires under it. Make sure that you don't have any that are coming out of the back of the pins. If you do, it will not send the proper signal to the ecu's and can cause the problem your having. Also have a look at the connections for the the O2 sensors. Those are located under the air box and oil filter. Check those for the same thing. The wiring in Ferrari's is known to be less than desirable. If everything in the wiring checks out fine then go ahead and replace the part. Also make sure that the connections are clean and making good contact while your at it.

 

I put a ground around the shell of the o2 sensor...as suggestion by a couple of people on this forum. used a hose clamp with a ground wire attached to it. Anybody else done this?

 

Also, as a lambda sensor ages, the response slows down, it becomes ‘lazy’ in it’s sinusoidal voltage trace. This is just a bad sensor.

Which really means ‘don’t ignore it’, as only proper diagnosis will reveal actual cause.

The ‘common problem’ in 348s is more likely electrical ground and pin connector issues. The 348 is no more or less susceptible to bad o2 sensors, it the actual electrical system itself. That said, proper preventative maintenance including cleaning contacts at connectors and grounds, plus proper diagnostics will go a very long way in maintaining reliability for your 348.

Best regards,

Rob

 

Did this as a crutch in '93-'94 on Challenge cars before we sorted the ground issues.

It can help as the ground circuit requires less than 2 ohms.

Best regards,

Rob

 

Good, I hope it stays out. I have always felt that it is better to find and resolve the issue (as can almost always be done) if possible than to resort to the electrical tape over the light.

 

When you recalibrated the ecu's, you did do it after the car sat all night, right? You need to make sure that the engine is stone cold when you do this. Since you did recalibrate the ecu's, you may need to adjust the idle control screw. It is really easy to do. If you look on the throttle linkage you will see the screw. Turn the car on and let it go through it's normal warm-up. Once the cooling fans have kicked on at least once your car should be plenty warm. After it is warm then you can mess around with the idle screw. Just turn it until you get the idle to the proper rpm's. Have fun. A word of caution, DO NOT mess with the screws that are on the throttle bodies. Only use the screw that is on the linkage

 

Yeah if you let it sit for about six hours you'll be okay. If I remember correct the screw should be close to the air box. I can't remember if it is on the right or left side. Oh now that I think of it, before you mess with the idle screw have a look at the vacume tubes. Make sure that all of them are hooked up. If they all are hooked up propperly and you still have the problem then mess with the screw.

 

Sorry but I'm not at home to look at the manual.

 

Okay I gave you some mixxed up info on the idle adjustment. Last night when I got home I looked at the manual, well The adjustment screw I was talking about only adjusts the throttle linkage. If you look on C34, you'll see the diagram. The screw I was telling you about is number 5, the one you really need to adjust is number 4. You will need to loosen the lock nut, number 3. To get to the adjustment screws on both throttle bodies you will have to remove the tubes that are connected to the mas air flow sensors. However given all this info, you did say that the guys at the shop already adjusted the throttle bodies, so I wouldn't mess with the adjustment screws on the throttle bodies. The reason is that they also adjust the CO and NO gases. So if you get them out of balance you can screw up the exhaust emissions on your car. But if you want you can mess with adjustment screw number 5 to see what it does to the idle. You want the idle to be around 950 rpm. Just remember how many turns you use, so that if its doesn't do anything you can put it back to were it was originally set. But as I said before have a look at your vacume lines. You will see two of them on the front of the plenum and one on the back. The one on the back is for the intake comensation valve, and the two on the front are for the fuel pressure regulators. Check those out before you mess with any adjustments.