New Cats and lambdas causing heavy misfire and loss of idle...?

Hi All,

As part of putting my Range Rover back on the road, I had the cats replaced with some second hand items. Unfortunately according to the garage the lambda sensors were a different fitting so they put in new ones.

Since then then car has suffered an intermittent problem with power (feels like serious fuel starvation that comes and goes) and a random loss of idle. It's weird because it is intermittent. It literally comes and goes. When it's behaving it pulls, runs and idles perfectly.

I hadn't quite made the connection before, but is it possible that an electrical connection problem with the new lambdas could have such dramatic effects? Or even a problem with the new lambdas themselves? I thought they just allowed for gradual changes to the fuel trims?

I originally thought the problem must be petrol system related as it runs fine on lpg (other than the unrelated problems in my other thread), but this has got me wondering now if it might be something more simple...?

Wouldn't a bad connection to a lambda cause the EML light to come on or something though?

Have you got a diagnostic? (I think they will show this won't they?) If not you should be able to test with a volt meter - a long while since I looked, but believe the usual practice with Oxygen sensors is a low voltage output for lean and a higher voltage for rich. I think the output would be up to about 1.5V - low would be < 0.7V and high would be over IIRC. The secret is perhaps to compare the two as it's unlikely both would be faulty. If an output wire is broken or the sensor faulty and you have 0V, the computer would think the engine's too lean and consequently you'd end up with a really rich mix! I've never really stopped to think how it would handle one bank that it thinks is lean and one that it thinks is normal, but I guess confusion and lumpy running!

I'd check to make sure the lambda sensors are plugged in properly also did they get anti sieze on the sensor head and not just on the thread ?

Make sure correct sensor was fitted, think Thor and Gems are very different electrically and some manufacturers list them as the same.

+1 on all the above. Also if you have diagnostics do an Adaptive Reset.

ady014 said:

Make sure correct sensor was fitted, think Thor and Gems are very different electrically and some manufacturers list them as the same.

Click to expand...

I think yours is on the turn from GEMS to Thor engines. Earlier Gems have Titania O2 sensors that read from 1 to 5v volts where as the later Thor have Zirconia sensors that read from 0v to .8v two totally different systems. Gems engines can take a long time to settle after major surgery to the fuelling side unless you do an adaptive reset. If not run it on petrol only for a good milage (100) to make sure its settled before using the gas.
Thor engines are a lot better at adapting, so much shorter distance required or again an adaptive reset.