Poor economy and trouble starting when cold.

[tt82]

Originally Posted by 960kg

......you mention the car had a new O2 sensor fitted before you obtained it was a Universal fitted with wires crimped as this would be the problem .....it should be the proper full length wire with the plug to be plugged in on the rear engine compartment bulkhead......as well as poor economy you may even get other problems if not the recommended sensor.....what engine and miles has it done?......when i had the 960 a bad O2 sensor gave me 10mpg ........

Will have to check the sensor, anybody with vadis who could show me where to look would be a great help.


The work was done Bickets in Kilmarnock on 18/03/2008 with 38389 miles on the clock. Bickets according to the reciept at the time were a Jeep/Seat Dealers.

Reciept states -

Engine Mangement Light on
Check voltage and check wiring and ground, found
1/1 02 sensor internal fault, supply and fit bank
1/02 sensor, fault still showing for 1/2
downstream 02 sensor, fit new sensor and roadtest,
found ok, cleaned idle control valve test found
ok. Lubricate accelerator pedal and linkage
030611510 Lambda Sond £154.50
030630132 Lambda sond £121.50

Also have a reciept for a new Air Mass Meter from Galloways Auto Repair Centre, Brodick, Isle of Arran. Date is 19/01/08 and mileage not recorded.

Car is now on 76k miles and I bought it on 41k miles.
Tbh when i first got the car in march 09 I'm positive I could get high 30's on a motorway run and averaged around low 30's. It seems to have steadily declined though.

[960kg]

....i checked your part numbers with Vadis for the sensors and they are correct so you do have Volvo ones.......i don`t think you have much left to replace!!.......have you ever thought that you have nearly doubled your mileage since you have had the motor so something has to give!... it cannot stay at 100% whatever........the performance of O2 sensors will gradually diminish over the miles and apart from your right foot these sensors alter the fuel rate to suit the emmissions so if your light is not on all is ok......try a bottle of STP in the tank and give it a blast to get rid of the crap carbon inside hanging around the valves etc.....

[tt82]

Well natrually you expect components to wear and need replacing, nothing last forever but I'd be astounded if O2 sensors had a life span of 40,000 miles. I do use redex frequently and have put in a de-coking treatment when the economy first started dropping.

[960kg]

Originally Posted by tt82

Well natrually you expect components to wear and need replacing, nothing last forever but I'd be astounded if O2 sensors had a life span of 40,000 miles. I do use redex frequently and have put in a de-coking treatment when the economy first started dropping.

.....your receipt states an internal fault with an O2 sensor at 38000 the manufacturers state between 60000 and 100000 they can need replacing, so who know`s when they do when an error code comes up???

[tt82]

Well thats the Fuel Pressure Regulator, HT Leads & Coils and Thermostat changed and if anything its got worse. 56 mile motorway trip this morning and my best average mpg according to the info centre was 31.6. Have just disconnected the battery before i head back home tonight, will see if a reset makes any difference? Something that i seem to have noticed is that the engine runs and feels best when cold and seems to get worse when its hot. When i pulled of the motorway i had dropped from 31.6 to 31.4 despite maintaining a steady speed on a motorway with no inclines. Just nice flat road. Could this be the lambda sensor getting worse as the exhaust gets hotter?

[Dog_Book]

Have the emissions tested, the last mot mine was very close to a fail yet for years past it sailed through. then 2 months after the o2 sensor failed, replaced it then my mpg went up Oo

[tt82]

Just remebered. Went to visit Classicswede last summer to get a price for getting my car converted to lpg, whilst there he plugged a diagnostic machine into it and siad the injectors were "plusing"? Could this also be related to the Lambda sensors.

[tt82]

Just had the MOT done and the emmisions report shows the emissions to be ok, would of thought if i had lambda sensor issues they would be out.

Fast Idle Test.....Min Limit..........Max Limit.............Actual Value
RPM......1/min......2500....................3000
CO........% vol................................0.200.......... ..................0.007
HC......ppm vol................................200............ ...................4
Lambda...............0.970....................1.03 0............................1.004

Natural Idle
RPM......1/min......450.....................1500
CO........% vol................................0.300.......... ..................0.002

[960kg]

......why do you so believe in your info centre?....it is only a guide....the mpg figures only relate to your present throttle opening, in otherwords if your travelling at 60mph with your throttle at a certain amount you will only do to the gallon what the info centre says so long as you don`t move your right foot or alter the speed of the car.....when you came off the motorway you say you dropped .2 from 31.6 to 31.4......do you really take notice of such irrevelant numbers?.....they mean nothing as the info centre is merely moving to the next revelant set of numbers because you moved your throttle or right foot......if you want to maximise on fuel use the cruise control if you have it and watch the info centre alter it`s didgits on it`s own according to what the ECU suggests......you will find it will move less than you could do with your foot in otherwords the cruise control is quite accurate and does what it is designed to do......your emmission readings tell you that the O2 sensors must be ok, but you already know that because your Lambda light is not on!!...

[tt82]

Its not just the info centre 960kg. I notice by how much fuel I put in and how few miles are on the tripometer. I'm sure when i first bought the car I could easily average mid 30's mpg.