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[mkaminski100]

I have a problem with high petrol consumption in my X20XEV. I found that even thought MAF has proper readings; there is no engine reaction when disconnected. When it’s cold it might choke when connecting, but apart from that engine runs at the same speed.
I drove my Omega with MAF disconnected and there is just a little bit less power, but I found that when it’s connected it is weaker than 2.2.
What is wrong? Is it MAF itself or the mixture is rich because of other sensor and when disconnecting MAF, it will not change much.
Please help me, or I will have to sell my baby…don’t need 2.0 power with 3.2 consumption…

[Auto Addict]

2.0 / 2.2's are not a lot better on petrol consumption than the 6 pots.

[mkaminski100]

I also have 2.2 auto and there's a big difference in petrol consumption.
Mine is up to 30MPG on motorway, 2.2 is 40MPG.
70% town + 30% motorway: my 2.0 is doing 20MPG while 2.2 is doing more than 28MPG.
So 2.2 is doing ca 8MPG more than mine.
I think that that my 2.0 is weaker in low revs.

[Auto Addict]

The 2.2 does have more torque.

Have you cleaned out the breathers/throttle body, new spark plugs etc..changed the fuel filter?

[mkaminski100]

Yes, I did everything apart from new fuel filter, but I think in this case it would have less power in higher revs.

[Pilly]

Disconnecting the MAF sensor does not mean anything, I had the same with my Jag, if you disconnect the MAF the ECU uses a back up program that can over ride this, most modern ECU’s have a back up program in case anything gets disconnected when the car is in motion which stops it cutting out at high speed.
I also had trouble with my Jag burning to much fuel and rough running, it turned out to be the oxygen sensors two on a Jag, and I did find a very good site explaining oxygen sensors here.

http://www.lambdasensor.com/

Tells you how to test them aswell  

[Marks DTM Calib]

Disconnecting the MAF will put the engine onto default values, this tells you that there is some sensor or fault causing the fuel/ignition maps to be in-correct.

What values are you getting for the MAF?


Here are a few test values for the MAF:


Ignition OFF, Disconnect wiring harness connector from P44 Air Mass Meter, Ignition ON. Measure voltage between the following terminals:

Wiring harness connector (wiring harness side) terminal 3 & 0V. Should be greater than 11 V

Wiring harness connector (wiring harness side) terminal 3 and terminal 1. Should be greater than 11 V  

Wiring harness connector (wiring harness side) terminal 4 & 0V.
Should be 4.8 ... 5.2 V  

Wiring harness connector (wiring harness side) terminal 2 & 0V.
Should be less than 0.3V


These are the basic checks.....

I assume that the coolant temp is reading ok and that the thermostat is ok , the engine temp gets upto 90ish when actualy moving?

The MAF reading varies as expected when applying throttle?

[mkaminski100]

My Vectra B (1999) had same engine, and when MAF was disconected, revs were going down, engine was choking but ECU was changing tha software (adapting) and revs were slightly higher than on idle.
There is no reaction in mine.
My lambda is going from 40mV to almost 5000mV in 0,5 sec periods Might stop highl/low for a second when accelerating but apart from that is always going max/min.  - is it ok for this engine?
MAF is 0.38 to 5.86V and 10.2-300.9 kg/h (idle, 5000revs) - values from OpelScanner.
Engine temp is about 82-84 when moving. I changed third thermostat and same values (2 new - vernet and MotoRad). I found that when the fan turns on at 95 degrees, but it takes ages to get the engine to 95 and it never reaches this temp in when moving. So there is no way that the fan is cooling the engine. Is it possible that both sensors in the engine are faulty and showing 10 degrees less? Engine is running on 90-95 while both sensors are showing 80-85, whent the temp reaches 105 fan goes on (sensor reading 95)

[Marks DTM Calib]

My Vectra B (1999) had same engine, and when MAF was disconected, revs were going down, engine was choking but ECU was changing tha software (adapting) and revs were slightly higher than on idle.
There is no reaction in mine.
My lambda is going from 40mV to almost 5000mV in 0,5 sec periods Might stop highl/low for a second when accelerating but apart from that is always going max/min.  - is it ok for this engine?
MAF is 0.38 to 5.86V and 10.2-300.9 kg/h (idle, 5000revs) - values from OpelScanner.
Engine temp is about 82-84 when moving. I changed third thermostat and same values (2 new - vernet and MotoRad). I found that when the fan turns on at 95 degrees, but it takes ages to get the engine to 95 and it never reaches this temp in when moving. So there is no way that the fan is cooling the engine. Is it possible that both sensors in the engine are faulty and showing 10 degrees less? Engine is running on 90-95 while both sensors are showing 80-85, whent the temp reaches 105 fan goes on (sensor reading 95)

Did you change the thermostat and housing or just the stat insert?

[mkaminski100]

Thermostat and housing, as always. Had a GM genuine, changed to MotoRad, then to Vernet and back to MotoRad again and no effect.
Isn't in suspicious that the fan starts at 95 and it takes ages to warm engine up to 95?

[cem_devecioglu]

As Mark as said without MAF, ECU will use default values which will fail

only in important temperature variations from the predefined...


In order to see the difference with a healthy MAF

overall engine condition must be very good..

Before changing it I replaced many parts and all of the sensors (except knock) including lambdas..

Performance change was visible after with the new MAF..

[mkaminski100]

Have you checked all sensors before replacing them? I am wondering about your old O2 sensor readings as well as the MAF sensor.
There are jus to many suspects to change without finding out what's wrong. O2 sensor, MAF, injectors, autobox, temp sensors, mid exhaus box, ignition, filter, engine head, wear of the engine...It can be enything.
Thats why I want to find out if there is any reaction when MAF is disconected and if there is, my engine is running in "emergency mode" all the time. This will help me to eliminate few things (like autobox)

[cem_devecioglu]

As my car is 10 years old..I dont worry about the parts I've replaced..

after the change I see all of them was necessary..


thermostat, CTS, TPS, cam sensor, crank sensor,lambda sensors

and finally MAF..


Thermostat -engine start to warm up quickly..And dont

get too hot in summer..

CTS- fuel consumption dropped down..

cam sensor - not very visible difference only smoother idle..

TPS - no visible difference..

lambda sensors - idle become normal, consumption dropped, performance increase..

MAF -consumption increase, performance increase..


ps: reference for consumption values are road comp..