172 mpg down just checking if my plan of action is right

[Dblock]

So basically,

My ph2 172 is down on mpg bad its averaging 31mpg and Im not driving it like an idiot. Now at 60mph in 5th it used to when I had my decat on get (or say it got) 45-50mpg and now it says 35mpg . My car is remapped using the RStuner and with the decat on I never got a CEL.

So does the RStuner turn on the CEL lamp for the lamba sensor? Im guessing my pap mpg is due to the lamba. Which lamba should I replace? Both? will Euro car parts be ok or is it much like the spark plugs and coil packs that it needs to be OEM?

If not the lamba what else could it be?

Thanks again

:star:

 

[thenorth]

The front lambda

 

[theduck]

Pre cat lambda

 

[wifey]

i have had loads of problems with my coolent temp sensor and sprak plugs and lmabada and i had no light on the dash but there where fault codes stored in the ecu

have you run a fault code check to see whats a matter before you go replacing parts??

and it may just need a good service and a good tharshing with some good fuel e.g. optimax and some injecter cleaner etc


regards

 

[Dblock]

i have had loads of problems with my coolent temp sensor and sprak plugs and lmabada and i had no light on the dash but there where fault codes stored in the ecu

have you run a fault code check to see whats a matter before you go replacing parts??

and it may just need a good service and a good tharshing with some good fuel e.g. optimax and some injecter cleaner etc


regards

I changed the spark plugs and coil packs about 10k miles ago as a precaution made no difference to running then but mpg was fine back then.

After 10mins or so i can rev it to 7500 so surely the coolant sensor is working no? Temp gauge is at the middle when warm and solid there. RStuner not showing any faults. I service my car every 6k miles so I doubt thats the problem.

Thank you duck OEM or pattern?

 

[theduck]

Iirc recommnended replacement is Bosch. I'd be swapping post and pre cat lambda round first though to if it cures it. If it does jobs a good un, if not the problems elsewhere.

 

[Dblock]

Cheers mate, it's shame they so bloody expensive. Will report back once done thanks again.

Iirc recommnended replacement is Bosch. I'd be swapping post and pre cat lambda round first though to if it cures it. If it does jobs a good un, if not the problems elsewhere.

 

[wifey]

at sutton auto factors the differnace between the cheap one and the bosch one was a fiver lol so bosch all the way, i paid £47 or £49 in total which isnt to bad i thought

regards

 

[Dean0o0o.]

I've got the same issue mate. I've fitted a new lambda and spark plugs but the low mpg continues (current avg is 30mpg). Also have a cold start issue, it sometimes doesnt start first time. Wondering if the 2 are related. I heard coolant sensors are common so I will try this aswell as a TDC sensor which shouldn't take long to change.

 

[Dblock]

So a little update, I've changed my exhaust as my old one was blowing. Fitted a decat and changed the pre cat lamba. At 50mph it shoot up to about 45-50mpg but when going 60mph it starts about 27mpg and climbs up to about 36 and at 70mph I average about 35mpg. Now that's better than what I was getting before.

I'm thinking about changing the post lambda sensor but I'm thinking that might only be for emissions and not control fueling unless I'm wrong? Anything else I can change? My car fully warms up after 10-15mins so I'm not sure if changing the thermostat or coolant temp sensor will make a difference.

 

[Dblock]

anyone? Does the second lambda have anything to do with fueling. it shouldnt do though should it?

 

[thenorth]

anyone? Does the second lambda have anything to do with fueling. it shouldnt do though should it?

Second (post cat / downstream) lambda sensor is only there to monitor emissions it does not effect fueling

 

[Dblock]

Second (post cat / downstream) lambda sensor is only there to monitor emissions it does not effect fueling

Cheers mate I thought as much. At least I dont have to change that.

 

[Dblock]

Im going to clean my air filter too just incase.

Does anyone know if by using live view? in the rstuner I can check if my pre cat lambda is working properly?

So if its not that is it just coolant sensor and thermostat?

 

[Dblock]

Right cleaned my pipercross filter, sprayed it with the orange smelling cleaning solution. massaged it in then filled up a sink and washed it. Had to do this twice as the first time the water went black! Second time it was a murky grey colour but then I rinsed it out fully. Car was showing 40.5mpg at 70mph but Il have to confirm this over the next few days.

 

[Zimma77]

Did cleaning the air filter help?

 

[Goodj]

check your tyre pressures too

 

[Stumpy]

Mine's running with a similar MPG to yours before you changed the lambda. I reckon that could be the problem with mine too.

Out of interest, is there a way of checking the lambda without replacing it?
Is there a certain resistance range that the sensor should have that can be checked?