Lambda Sensor
I have a 1993 300GE and recently had a custom exhaust fitted -stainless steel for £700 which included VAT and Cat -up to the pipe under the drivers front wheel -on the face of it a reasonable;e price.
I was however servicing the G and noticed that despite my instructions to the installer, he removed and failed to replace the lambda sensor.
The G drives very well and uses a little extra juice (but that may be because my right foot has become a little heavier so i can hear the notes of a straight 6). I am however concerned that I might damage the engine/cat if I continue to use the G without the sensor .
Any advice anyone on the potential effect on the engine?
Incidentally, there is a switch in the engine to advance the timing if using less than 95 RON unleaded -I mention this for completeness
Many thanks
David
The fuel system on the 300GE is the Bosch KE Jetronic. It functions primarily mechanically, but fine tuning of the mixture is carried out with feedback from the lambda sensor. Without this, the fuel-system will run open-loop and although you will be unlikely to damage the engine, you will not get the best fuel efficiency/performance. Without feedback from the lambda sensor, the system could err towards too rich or too lean.
The ignition system is not equipped with knock sensors, which would allow automatic ignition adjustment up to just before the point of pre-ingnition. There are two fixed maps available, selected by the timing plug that you mentioned.
The fitting of the cats closer to the exhaust manifold will permit faster warm-up, but in the wheel arch (If I understood your post correctly) they could fail from thermal shock from water spray from the tyres. Newer models have the cats almost as part of the exhaust manifold in the engine bay, but not wheel arch.
Probably not a bad deal for the price paid, but with the omission of the lambda sensor, I would go back and have some words with the fitter. A new factory system is around £3,500 - ask me how I know.
The lambda sensor can be found as a Bosch part from the likes of Euro Car Parts , but you may need to swap over the plug from your original one. Else very expensive from MB (around £400 IIRC).
see page 32: http://vwts.ru/injector/k-jetronic/gasoline_fuel_injection_system_k-jetronic_eng.pdf
(This is a K-Jetronic, not KE, but it describes the function of the lambda sensor)
The system is unlikely to deviate out of safe operating regions without the sensor, but an engine running too lean can suffer from thermal damage and one running too rich can dilute the engine oil with wash-down of unburnt fuel and feed unburnt fuel into the catalytic converter which could cause thermal meltdown of the internal ceramic matrix. All extreme cases, of course.
I am surprised that acceleration and pick up on kick down has not been affected by the removal of the Lamda sensor.
Maybe, but I don't think the response time of the Lambda sensors is very fast, and in the KE Jetronic system it's used for a gradual tweaking of the fuel/air mixture.
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Thank you very much for your excellent information - I will take it up with the fitter
Best wishes
David