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Discussion Starter #1
I have a 1997 bmw 323 coupe and the emissions are well too high to pass an mot, tee guy says that the CO should be less then 0.3% but my car is running at well over 3%, i dont have any lamba sensors connected as these were knackered so i changed them to see if it helped and they made the car run lumpy and the emissions went higher, does anyone know why they would do this and why the emssions may be that high also, i have changed the cat for the 328 ones so i dont think its the cat but could be wrong. Any help or advice is highly appreciated cheers.
 

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I have a 1997 bmw 323 coupe and the emissions are well too high to pass an mot, tee guy says that the CO should be less then 0.3% but my car is running at well over 3%, i dont have any lamba sensors connected as these were knackered so i changed them to see if it helped and they made the car run lumpy and the emissions went higher, does anyone know why they would do this and why the emssions may be that high also, i have changed the cat for the 328 ones so i dont think its the cat but could be wrong. Any help or advice is highly appreciated cheers.

did u change the cat after you re-connected the O2 sensors? what I mean is- have u been running the car with the 328 cat with no O2 sensors?

If so then the cat maybe buggered, the O2 sensors are in place to protect the cat, also what O2 sensors did u get? Bosch? many after market ones are useless.

I'm not taking the piddle or anything.........but when you reconnected the O2 sensors- did u connect them up te right way round ie the pre-cat sensor screwed in before the cat...........I know this sounds stupid but we had a c ar come in last month where the chap changed the o2 sensors over himself- he used the Walker ones-----many after market ones come with exactly the same length cables, and what he did was screw the sensor onto the exhaust in the wrong positions..........the Bosch units have cables at just enough length so u don't make that mistake.
 

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I would also say the Cat will be knackered if you have driven the car with the Lambda sensors disconnected, the excess fuel would have over heated the Cat monolith :frown
 

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Discussion Starter #4
I have only just changed the cats because i have only just put the 328 exhaust on as it failed with the original 323 exhaust so i changed it but made no difference and i may have got the sensors wrong way round not 100% sure, but i wouldnt of thought that would have made any difference as there both on the down pipes
 

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I have only just changed the cats because i have only just put the 328 exhaust on as it failed with the original 323 exhaust so i changed it but made no difference and i may have got the sensors wrong way round not 100% sure, but i wouldnt of thought that would have made any difference as there both on the down pipes
Having the o2 sensors crossed will cause havoc with the fueling as the ecu adjusts the fueling according what readings are being picked-up from each bank by the o2 sensors.

Have you had a diagnostic scan done? which sensors are you using?

Do u have the actual figures from the emisions test i.e CO, HC and Lam readings......was it just the CO that was out?
 

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Hi mate,

Realoem is showing 2 x O2 sensors for an E36 328 and only one for an E36 323 and all are different part numbers, how may do u actually have on your 323?

I'm not really sure if the O2 sensors for a 323 and a 328 are interchangable and also the cat for the 323 and the 328 are completely different units (according to Realoem)

Personally mate, I would replace the cat with a 323 item and the o2 sensor with a 323 item.

but maybe Ronnie or any other BMW boffin could shed more light on this.
 

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323 and 328 both have same o2 sensors in the same manifolds front 3 cyls and the rear 3 cyls the 328 just has a twin exhaust with two cats from the manifolds back
so the 328 exhaust system is an easy mod with no issues

maybe the cats are knackered :mad
 

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Contrary to popular belief, Lambda sensors are not black magic.

You can test them relatively easily and reliably. With the sensor removed from the vehicle, you need a good voltmeter and a blowtorch. The torch test is very easy to do and extremely reliable. There is very little chance that a sensor will pass the torch test and not work when properly connected in the car. The following link gives good descriptions of the sensors, the torch test and tests for the heater. Much of the time its a 'one size fits all' thing. Any Bosch 4-wire sensor is the same as any other: only the wiring loom changes.

http://mymiata.paladinmicro.com/Miata4-WireO2.htm

Grafting the wiring onto a different loom is not a problem either if you have the brain power to make sure the correct wires are connected. They should be soldered and the joints sealed with heatshrink or self-amalg. The last time I had a sensor failure was ages ago on a Volvo and one from a scrap Saab just happened to come my way: it passed the torch test with flying colours and then the MoT.

Good quality new ones are relatively cheap: it's the correct plug on the one from the BMW Stealership that is expensive.
 
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