Engine 850: B5252S/2.4/10v: Missfire/plug leads

[LPGjonderby]

I didn't think it was likely on our older stuff, I know it does on newer cars. In particular sports stuff. Ah well, will leave it in sports though as I get to hear the engine roar so much more. Until he blows !!

Jon

[LPGjonderby]

Guys

Having had my S70 fault codes read last week, the water temp sensor & air temp sensor were replaced. The fault codes were erased.

It then ran fine for 3 days on petrol, then I tried running on LPG, this was fine until this morning. It has started to missfire again around 3,000 revs on petrol & gas.

At the time of having the codes read it was running very lean as the adaptive settings were out. This was reset and was fine. I can only assume the adaptive settings have started to go awol again and are leaning the mixture off.

Is this likely to be because of a faulty lambda sensor ?

The original one has done for 132k miles, how long do they usualy last ?

I have spotted a titanium one suitable for an S70 bi-fuel on ebay, any ideas if this item is any different to the standard S70 unit my car has?

Item number 250215145835

Thanks

Jon

[Mike_Brace]

A possibility is that when on lpg it is running far too rich causing the car's ecu to lean it down as far as it can and possibly still too rich on causing a misfire. Switch back to petrol and it would be running too lean. Could do with monitoring lambda on both fuels to see if this is the case.
If so it is likely that the gas injectors are worn.

Lambda sensors tend to fail on a fixed reading.

The lambda can be monitored using a digital voltmeter (black wire from the lambda sensor) I have a feeling on these they are an unusual one reading from 0.5v - 1.6v rather than the usual 0-1v. The higher the voltage the richer it is. On a correct mixture it should scan back and forth fairly rapidly. If too lean will remain relatively stable at the low voltage - rich stay at the high voltage.

Mike

[LPGjonderby]

Thanks Mike

That makes some sense to me ! Alas I do not have a working volt meter !

Having removed the ECU's over last night. The car is again running fine this morning.

What I don't really want to do is replace the lambda, then find it is yet again missing the same as before and before etc.

Although there was a fault code found for the lambda last week, but this was related to the adaptive settings. However I am told by the LPG installers that the gas system does not take any readings from the lambda when on gas.

Looks like I will be ordering a new lambda then !!!

Jon

[classicswede]

Don't bother ordering a new lambda as I'm very doubtfull that is teh fault.

Your installer is right and wrong with what he has said. The gas system does not directly look at the lambda but does lambda ajustment through the ecu.

For example if the lambda see's a rich fuel mixture it will reduce the petrol injection times and as the gas ecu reads the petrol times it will then reduce the LPG times leaning off the fuel mixture.
After the ecu has trimmed down to compensate for the over rich mixture and you switch back to petrol the ecu will suddenly find itself lean.

To me it sounds like the LPG system has a fault or just needs adjusting.

[LPGjonderby]

To be fair I am getting lost with this one.

This morning it ran like a dream on LPG, whether this was because I pulled the ECU's last night, who knows ?

Tonight the missfire is back, big time.

Shaking the car between 2 & 3,000 revs. Again tho' if you thrash it no problems. Its always when driving just on throttle, or excelerating slowly.

Everything has now been changed, apart from the lambda sensor !

I need to take a trip up those hills to Leek and visit the gas installers !

Problem is I love the old bag, if he didn't have this missfire that won't be cured he would be nearly perfect. Apart from the ABS, TRACS bla de blah !!!

The gas people assure me that no information is taken from the lambda when running on gas so am at a loss.

I can only assume the adaptive settings keep running out, which could be the LPG or cars ECU's.

Thanks guys

Jon

[Mike_Brace]

I think the fact that you have proved twice that it runs fine on petrol that it is not a petrol fault. The gas system can be connected to the engines temperature sensors (they also supply an optional inline sensor if required) If the old temp sensor was faulty and replaced this will throw the gas calibrations out as they need setting to the sensor. As them to recalibrate to temp sensor and also reclibrate the sytem itself. That should hopefully sort it out.

Mike

[LPGjonderby]

Originally Posted by Mike_Brace

I think the fact that you have proved twice that it runs fine on petrol that it is not a petrol fault. The gas system can be connected to the engines temperature sensors (they also supply an optional inline sensor if required) If the old temp sensor was faulty and replaced this will throw the gas calibrations out as they need setting to the sensor. As them to recalibrate to temp sensor and also reclibrate the sytem itself. That should hopefully sort it out.

Mike

Will give them a call tomo', many thanks Mike. Will keep you posted. Jon