Common causes of lambda dropout
Discussion
In an attempt to distract from my previous faux pas, please can you let me know common causes of the lambda sensor readout dropping to near zero?
The connectors are in good health, the sensor heater grounds are now solid (adding in this mod made the sensors work from a cold start but after 30 secs or so dropped out again). Blipping the throttle brings them back briefly. I'll take it for a spin tomorow to see how it behaves on the road.
Exhaust smells rich as adaptives go up so I'm fairly sure vac leaks are not the cause.
The connectors are in good health, the sensor heater grounds are now solid (adding in this mod made the sensors work from a cold start but after 30 secs or so dropped out again). Blipping the throttle brings them back briefly. I'll take it for a spin tomorow to see how it behaves on the road.
Exhaust smells rich as adaptives go up so I'm fairly sure vac leaks are not the cause.
Tanguero said:
If the reading from the sensors is normal to start with, then bottoms out and your exhaust smells rich it could well be that the sensor is working and giving the correct reading in a very rich environment. That said the sensors do fail. Chicken or egg?
A reading at the bottom of the scale indicates a lean condition and the adaptives top out richening the mixture. This could be a vac leak scenario in that the exhaust actually IS lean but given the air flow readings, and tps is good, and the smell and the clouds of steam from the exhaust, I don't think so.I have a pair of new sensors to go in, trying the generic titania ones from justlambda, you can all laugh at me when they last 5 mins
It occurred to me while digesting my Christmas lunch that the lambda sensors don't measure the amount of fuel in the exhaust, they measure the amount of oxygen.
Having read someone else's account of the difference made by re-sealing the throttle bodies to the cylinder head, I put two and two together and realised that if one or more intake ports have vacuum leaks, the sensors will read lean and send the mixture up, causing the remaining cylinder(s) to run rich.
I had observed, as had the previous poster, that idle quality improved as the engine warmed up - presumably metalwork expanding and sealing some of the vac leaks.
So yesterday i removed my throttles, cleaned up the mating faces and applied silicone. This was actually a pretty easy job but a must-have tool is a ball-ended allen key with only the lower front corner and upper rear corner bolts presenting any real access issues. I removed the fuel rail and all the throttles as a single unit - apart form the 24 bolts, the only things to disconnect are the throttle cable and the front vac hose - everything else has enough slack to allow access.
Today even before re-setting my throttles, the (very) cold start idle quality was noticably improved. Unfortunately I wasn't able to take the car out for a spin, but set the throttles up properly once again. The lambdas are still droppig out but stay in touch with the ECU for long enough to allow the adaptives to start dropping from their maxed out position.
Here's hoping a good run will clear things up.
Having read someone else's account of the difference made by re-sealing the throttle bodies to the cylinder head, I put two and two together and realised that if one or more intake ports have vacuum leaks, the sensors will read lean and send the mixture up, causing the remaining cylinder(s) to run rich.
I had observed, as had the previous poster, that idle quality improved as the engine warmed up - presumably metalwork expanding and sealing some of the vac leaks.
So yesterday i removed my throttles, cleaned up the mating faces and applied silicone. This was actually a pretty easy job but a must-have tool is a ball-ended allen key with only the lower front corner and upper rear corner bolts presenting any real access issues. I removed the fuel rail and all the throttles as a single unit - apart form the 24 bolts, the only things to disconnect are the throttle cable and the front vac hose - everything else has enough slack to allow access.
Today even before re-setting my throttles, the (very) cold start idle quality was noticably improved. Unfortunately I wasn't able to take the car out for a spin, but set the throttles up properly once again. The lambdas are still droppig out but stay in touch with the ECU for long enough to allow the adaptives to start dropping from their maxed out position.
Here's hoping a good run will clear things up.
Gassing Station | Cerbera | Top of Page | What's New | My Stuff