replaced lambda sensors.... misfiring & sooty deposits??

[orangeone]

Just wondering if any of you guys can shed some light on a problem that has occured since changing both my lambda sensors on my MK1 2000 tuscan.

The car had previously been displying the efi warning buzzer on a regular basis just before the mot ran out. I took the car for the MOT and the garage confirmed that the emmisions were off the scale and recommended replacing the sensors.(Just a note to say before the MOT the car seemed to be running ok)and after trolling through the forums deducted that it was very likely to be the sensor.

I replaced the 2 lamba sensors which i sourced of the internet.)(NTK Sagem 3 wire)a direct like for like replacement.After fitment and 40 minute drive the following seems to have occured.(note that one of the sensors seemed very sooty when taken out, the other was relitively clean)

1. The idle speed has dropped slightly to 400 rpm from the usual 500-600 when warm
2. The efi buzzer came on about 3 times as per before.
3. There was hesitancey in acceleration at about 2500.
4. When i got home,i noticed when revving the car at 2500 and standing at the rear of the car, the near side exhaust was very sooty around the exit
of the carbon can and smokey, but didnt seem to pop exessively. The drivers sidehowever was not smokey, and had no sooty deposits at all, but it did produce some very regular loudish bangs and pops(misfire?).

Once again just wondered whether as usual one of you guys could shed some light on the possible fault !

Many Thanks
Gary

[trackcar]

sounds to me like youve got them connected the wrong way around, so the ecu is richening the three cylinders which are already too rich, and weakening the three cylinders which are already too weak .. check on the lambda wirs that you have them connected to the correct manifold.

The other issue is that the NTK 3 wire lambda is NOT the correct replacement .. the correct replacement is a modified version of what you have bought, with a high temp ceramic internal insulator rather than the std version which melts at high temperatures.

[orangeone]

thanks for the info trackcar. I thought you couldnt get the wires mixed up
because the lambdas come with a fitted round plug with a locator on the inside of the plug to make sure that you cant fit it the wrong way round? Is that what you meant.

Cheers
Gary

[trackcar]

nope erm what I meant is have you got the wire for the front three cylinders' lambda sensor going to the rear lambda sensor ..

[Fume Troll]

You can definitely get the wires mixed up, the large white connectors are both the same. A bit further into the loom though (the car side, not the sensor side) the wires leading to the sensors should be tagged. Need to be careful though, as mine are tagged "lambda even" and "lambda odd" which obviously isn't the case!

Cheers,

FT.

[Fume Troll]

Just to add: If the car has been running with faulty sensors the adaptive maps are quite probably all over the place, so even replacing the sensors may not cure the problem.

Cheers,

FT.

[orangeone]

Thanks for the info guys, with reference to the adaptive maps? Sorry to sound like a complete
thicko FT, what are the maps? what do they do and how do you correct them.

Cheers
Gary

[Fume Troll]

The map is the table of figures that the ECU reads to decide how to adjust the fueling etc for the car for any given combination of throttle position and engine speed. There is a base map which the ECU starts off with, but as things change (e.g. blocked air filter, dirty plugs etc) it makes adjustments to these figures to take account. Once you re-set all the changes etc, you need to re-set the maps so that the car starts again from scratch.

To re-set the maps you need to use the software available free from www.mytuscan.co.uk (when it's back up!). You also need a cable to connect to the diagnostic cable on your car to a suitable laptop or computer via a serial cable. Have a search on the forums, there's quite a lot of info. The software is really handy even if you don't change anything, as it logs sensor faults and things like that.

If you're not comfortable doing this, it sounds like a service at a good TVR specialist would help a lot!

Cheers,

FT.

[orangeone]

Thanks for keeping it basic FT, really appreciate the info. Looks like a service is inboud,

Many thanks.

Gary.

[ian_r]

yeh id go for throttle set up/reset adaptives.
Mine ran slightly rough, black smoked a little etc similar to yours and reset throttles and adaptive maps, reset throttle pots, tightened timing chains and she runs really well now.
I would say, that due to one of sensors being black to start with it was over-fueling before hand, and combined with dodgy 02 sensor's didnt realise. Clean the throttle butterflys, adjust throttles if neccessary then rest throttle pots and maps. ; )