Engine: 2.0 Carb B200K/B200F: Lambda sensor

[Volvodrivingbiker]

Lambda sensors

my 240 is a 20 injection.
The Lambda sensor light has come just before its Mot of course !
Ive been told by a mechanic to disconect it and take the bulb out the dash ,
surley it will not pass an MOT like that .

Has anbody had any expirience with them ?

[wooble]

the lambda light does not just mean a lambda sensor fault, it can indicate a wide range of faults. Use this guide to read your codes and report back.

Removing your lambda sensor/bulb will be an MOT fail, and cause your car to run horribly. I'd recommend replacing the mechanic with a non-defective one.

[tannachyallen]

depends why it has come on. Have you got any codes logged in the diagnostic unit?

Dave A.

beat me to it wooble....

[rippedoffagain]

On my previous 940, it used to come on quite often. The fault codes (can't remember which codes they were but I remember what they were telling me) said the signal from the lambda sensor was missing or out of range, and one telling the MAF signal was bad too. Great, the MAF and the lambda sensors both failing at the same time. How expensive.

I guess the ECU came to this conclusion on account of the fact that no matter what it tried to adjust the mix, there were still large amounts of unburned fuel and air coming out of the exhaust, therefore the sensor must be knackered right?

Well once I replaced the completely rotten dizzy cap and rotor arm and HT leads so that the fuel was actually being ignited properly, suddenly no more warning lights. Oh, and a significant increase in power, and massive improvement in MPG too.

[Volvodrivingbiker]

I didnt realise they had that modern a system in there thanks for that .
will the ECU & EZK codes be read from the same piont ?

[Volvodrivingbiker]

Wooble I'd recommend replacing the mechanic with a non-defective one.


I realy dont trust any garages round here now days to be honest

[wooble]

ECU ad EZK codes are read from sockets 2 and 6 respectively. Your first step should be to read codes from both, then clear them and see if they reoccur. Once you have determined a certain code is repeatedly occurring, you can identify and repair the fault.

I agree that a trustworthy mechanic is a hard find these days, but to suggest unplugging the lambda sensor and removing the bulb would be a fix isn't being a bad mechanic, it's pure idiocy.

[Volvodrivingbiker]

Ok ive followed the code sequence as discribed , I printed out the list and wrote down on it what was signaled it went like this

ECU ....... 1 - 2 - 1 ......... mass air flow meter signle faulty or missing
......... 2 - 1 - 2 ......... 02 Lambda sensorsignalmissing or faulty

EZK ........ 1 - 4 - 4 ............ Load signal from ECU missing

I then tried to clear the codes so i can see if it happens again but even after 10 seconds the led didnt come on to clear , could this be because the fault is still evident

im asuming the lambda fault came on now because i did unplug the sensor and run the engine not sure what to do next any ideas ?

[Volvodrivingbiker]

just pulled this from another site does it ring any bells to any of you with performance filters on .
this is not something ive done as my car is completly standard




Air intake on a volvo 240 (big lesson learned)
Well, when I first got the car I removed the factory airbox, and the manifold warm air intake pipe was missing, but the stove was on the manifold.

Put a "ricer" performance filter right onto the MAF sensor, short, simple, much less stuff under the hood, $5 more than a stock filter that was honestly plugged solid. Weight reduction and simplicity!

The wiring harness is getting bad and needs work, so I was blaming my runnability issues on that. Engine would randomly get bad fuel economy, from 20 city to 14 mpg city.... in a blink of a eye, and after a few months, started noticing that premium gas reduced the issue, and it was WAY WORSE in the rain.

Symptoms included, increased idle, (with the automatic in gear, it would fight to increase the idle from the load, and be having to hold the brake harder. Would unplug the idle control valve and use the thumb screw to hit a "driveable" balance to save that problem some. On damp days it was dumping so much fuel in the engine I could see black smoke in my rear view mirror, much to the displeasure of cars behind me.

Read up on HOW most of the ECU works in a Bosh LH-Jetronic fuel system, and learned that the MAF (mass air flow sensor) uses a "hot wire" module, so blowing colder, more turbulant intake air across it is bad mojo. Further checking and testing the factory airbox, the valve for bringing air in from the exhaust stove would try to maintain approx 40-50 degrees celcius, not just for startup.

In the MAF, the hot wire actually will glow red, and the air being pulled across it changes its temperature and resistance, sending a signal back to the computer indicating the MASS of air, accounting for density too, so when a puddle splashed my fancy looking air filter, it would WET DOWN the MAF and make it think a cold hurricane is blowing into the intake, and the computer would DUMP FUEL accordingly, also explaining the high idle that it couldnt work out, as the MAF was giving one reading and the O2 sensor was saying the opposite.

Put back in the factory airbox with it ONLY pulling air through the exhaust stove, giving it a nice warm flow at all times, and right away, it idles perfect. no confused ECU for 15-60 seconds on startup either.

Cant wait to see what new heights I get on my next tank of gas. will forgo my last two partial tanks in my log, because I know its well below average due to serious malfunction in heavy rain. Going to fill it tonight and should have a new city reading after 2-3 days of urban pizza delivery, and see just now much my other little mods (including timing advance, electric fan etc) have really helped.

So if you have a "HOT WIRE" style MAF sensor in your car, Warm air intake is your friend! Also, clean the MAF every few months, dirty one is less accurate as well

[tannachyallen]

I read this a couple of years ago. It put me off changing to a cone filter for a long while. However it contains quite a lot of bollocks. Hot wire MAFs are called so because they heat up on startup/shutdown to burn any crap off the wire and not because they like supercharged hot air which is what you will get if your old style filter box get stuck in the open position. This will quite simply fry your MAF. Hot wire MAFs are giving signals as to the air temperature=density so that the management can throw the right amount of fuel at the mix.

If you position your cone filter so that it gets warm ambient air in the engine bay you will find that all will work well. Sounds like the writer of the article had his where water could get on it while driving......well what does he expect to happen if he lets water get into an air intake?

I took the plunge after reading what Wooble and some others had done to their air filters. I am more than happy with the performance and simplicity of maintenence of my setup.

Dave A.