Hi all. I towed a caravan for the first time and spent most of the 90min journey with the auto in 3 (as the manual said to do that when towing). I don't know if its relevant but my following journey the next day was when this problem started.


After an hours drive, pulled up at services, then started car and it was struggling at idle - kept going to stall then it would rev up and catch itself. Then the engine management light came on. If I revved it up myself it seemed to help, but I think I got white smoke from exhaust (hard to tell as was dark). Drove home fine but with light still on.


Next day journey car really struggled, was juddering and nearly stalling at speed on motorway. Actually stalled once at a red light. Gave it some revs and all was well. Drove home fine later that night.


Since then I've done 2 more journeys with no problems but warning light still on. Got a code reader and I had these codes-




P0172 Powertrain System (Fuel control system) too Rich (Bank 1)
P0131 Powertrain O2 Sensor (Upstream) Circuit Low Voltage (or shorted to ground) (Bank 1 Sensor 1)


But with no symptoms I reset the codes. Went for a short drive with engine up to temp with no issues.


Read codes when I got back and I had


P2097 Powertrain Post Catalyst Fuel Trim System Too Rich bank1


Let it idle for a while, then checked codes again and its now got


P0171 Powertrain System (Fuel control system) too Lean (Bank 1)
P2097 Powertrain Post Catalyst Fuel Trim System Too Rich bank1


How can it go from too rich to too lean?


The code reader app also tells me
Misfire, fuel system, components, o2 sensor heater & EGR system checks are all complete
But
Catalyst and o2 sensor are incomplete. It says it may take several cold start journeys before these checks are completed. So I'm guessing I'll eventually get the car juddering again before it gives up and puts the oxygen error back on?


I've got no engine management light since I first cleared the codes. I had no error codes 1 month ago when I last checked.


This isn't my area of expertise so should I go around replacement sensors? Any advice to put me in the right direction would be great.
Thanks

 

Just a quick response that your problem has been on here not that long ago. Sounds like fuel pressure at rail again. Give a check back over threads.

 

It will cost nothing to keep an eye on coolant level over the next few weeks (along with any other checks you are making). If the level falls slowly over time, coolant is being consumed in some way. Putting together the hint of white smoke the day after your special journey in 3rd. gear, and the MIL lamp being lit showing contradictory data in the ercos, would make me think coolant is being lost to a combustion chamber. The giveaway of course -- is coolant being consumed?
Most likely cause is a blown head gasket from the higher revs in your 3rd gear journey.
Hence keeping an eye on coolant level.

Leedsman.

 

Thanks for the replies.

Went out again today and the engine management light is back on. Haven't noticed any coolant leaking but I'll keep an eye on it. Not seen any frothing either. I forgot to say when I saw the white smoke while revving it backfired, so I assumed this was unburnt fuel igniting. I've had this car running flat out at times to see how it performs, when towing the caravan it was a very gentle journey that I'm sure must've been less of a strain even though it was limited to 3 gears.

Codes I now have is
Current Fault P0171 Powertrain system too lean (Bank 1)
Pending Fault P2097 Post Catalyst Fuel Trim System too rich bank1

I can also view a live graph of the O2 sensors in the app.
Bank 1 Sensor 1 the O2 levels bounce around all over the place but on average are very low. Over time it gets lower and lower until the car starts juddering and then puts the light on.
Bank 1 Sensor 2 is a fairly constant high reading.
Both drop when I rev the car.

Are both of these O2 sensors lambda probes after the cat or is one before? Just wondering if the O2 is incorrectly being read as too low due to a faulty sensor so its then lowering the fuel to compensate?

Is it the same O2 sensor that makes it think the fuel is too rich (due to low O2)? This would tie in with the initial fault of P0131.

Starting to make my head spin!

 

I'm talking froth here Leedsman as I've just noticed its Petrol. Too much brake dust in my eyes.

 

Because lambda sensors work in very hostile conditions, and they measure free oxygen in the exhaust gas, I would look in this area next. 1st. thing, check connexions (due to the heat). Check wiring as far as you can. I don't know how to check these sensors themselves, maybe others here will know. Check the wiring up to the microprocessor board. The lambda sensors may be checkable by replacement only (Yes, there are times when substitution is the only way!)
Esure basics like sparkplugs, coils, clogged injectors etc. are working as they should.

Leedsman.

 

Thanks gonna replace the sensor now. Just a thought - Bank 1 sensor 1 is the one with intermittent readings isn't that upstream from the cat? Where abouts is it exactly?

 

Run a tin of BG44K in the fuel! This might do the trick

 

Powerenhancer discount code OCT20 for a 20% discount

 

Had a similar problem with my mums car! Chucking up all these codes with oxygen sensors ect! I banged in a tin of BG44K and it cured everything! Worked fir my mums car! Might do it for yours.