Technical Permanant MAF sensor diconnection

[57mmStroke]

Hello all,
My MAF sensor (105JTD 2001 122K miles) is causing the Multi to be very sluggish. Mechanic at garage disconnected it and car turned into a rocket again (well not a rocket, just normal Multi).
Quoted from Fiat MAF sensor price: 252.76 Pounds + Vat +50 Pounds Surcharge on old unit, and nearly fell over from hearing this price.
Question is: Does running the car with the MAF disconnected cause any long term problems?

Thanks for your replies

 

[Peat]

If you do replace your MAF sensor do not buy a repro unit as they invariably are just as bad as the unit you replace, if not worse. An OEM Bosch MAF sensor can be bought for much less than quoted and fitted by yourself in minutes.
Try cleaning if with Isopropanol before buying a new unit and make sure the air filter is clean.
FYI - http://www.import-car.com/Article/60923/Tech_Featu.aspx

HTH
Peat

 

[pondweed]

if you run with MAF disconnected it will not benefit from the fuel trimming it performs, so you'll do less to the gallon than when it is operating correctly.

 

[Oldschool]

if you run with MAF disconnected it will not benefit from the fuel trimming it performs, so you'll do less to the gallon than when it is operating correctly.

It still does do the fuel trim. It is still being controlled by the MAP.

Most of the cars runn better without the AFM especially when mapped.

Only problem is that you will have a warning light on, which does annoy some people.

 

[BikeDoc]

I thought a fuel injection system would use a MAF sensor or a MAP sensor, not (usually) both?
If the system 'loses' an input from a sensor (i.e. if it fails, or in this case, is disconnected), doesn't it revert to a 'back-up' setting or a last known 'good' setting?

 

[pondweed]

It still does do the fuel trim. It is still being controlled by the MAP.

Most of the cars runn better without the AFM especially when mapped.

Only problem is that you will have a warning light on, which does annoy some people.

ok.... but it does something that will result in more fuel being used because of the air mass then?

 

[martbass]

Hi
I unplugged my maf sensor connection for a couple of days as I thought it was suspect.
The car ran much better by far......but after a while I had the engine managment fault (yellow) light on constantly.
Assuming the maf was duff, I gave it a clean with a specialist cleaner and re plugged it in.
engine management light goes out..........no probs since.

Not sure if it will do damage running with the maf unplugged but I couldn't understand why I had the warning fault light on and didn't leave it unplugged for too long!

 

[Oldschool]

I thought a fuel injection system would use a MAF sensor or a MAP sensor, not (usually) both?
If the system 'loses' an input from a sensor (i.e. if it fails, or in this case, is disconnected), doesn't it revert to a 'back-up' setting or a last known 'good' setting?

On some engines they us now 2 MAPs and 1 AFM.

Not all sensors will send the ECU into the other 2 paths.

ok.... but it does something that will result in more fuel being used because of the air mass then?

Not necessarily. The ECU relies on both sensors. But either of them is adequate to run the engine. Many cars have either, but not both, which is adequate. The AFM is there to support info in order to fulfill regulations but is not essential for the running.

Hi
I unplugged my maf sensor connection for a couple of days as I thought it was suspect.
The car ran much better by far......but after a while I had the engine managment fault (yellow) light on constantly.
Assuming the maf was duff, I gave it a clean with a specialist cleaner and re plugged it in.
engine management light goes out..........no probs since.

Not sure if it will do damage running with the maf unplugged but I couldn't understand why I had the warning fault light on and didn't leave it unplugged for too long!

It won't do damage to the engine if the MAP is okay.

 

[57mmStroke]

Ok, Thanks for all of the responses above.

Is the AFM (the one right after the air filter) and the MAP two seperate units? where is the MAP located?

Engine runs well, and MIL light has not come on. On my model it is a red injector type lamp.

 

[SS069]

I don't know if this is relevant, but my 115 Multi was running sluggish & blowing excess smoke from the exhaust, I tried it with the MAF unplugged, the car ran a little better, but still slow with less smoke.

I then installed a new MAF sensor, still sluggish but no where near as much smike from the exhaust.........I'll be going down the EGR route next of should I too be looking at replacing the MAP sensors.............:bang:

Would it be worth while stripping & properly cleaning the induction system.....

 

[Peat]

Just blank off the EGR you will not regret it!

Peat

 

[SS069]

Just blank off the EGR you will not regret it!

Peat

Peat,

WILKO buddy, I love these forums with like minded folks helping each other out & best of all all the remedies have been tried, tested & prooved........

I'll let you know how I get on, once again thanks.....

Sean

 

[martbass]

I wondered if it would be an MOT failiure if you permanently blanked off the egr valve.........eg. the emisions test would fail?

 

[BikeDoc]

My Lucida went through two MOT tests with it's EGR removed completely, and that was an old (1992) diesel with a mechanical (not electronic) fuel system.
Newer engines should be fine.
Stick a dose of Redex in the tank a few days before it's MOT test to be safe. It's worth doing that regularly anyway.
Works out at approx £1.75 to treat each full tank of fuel if you buy the 1l bottle.

 

[Peat]

I wondered if it would be an MOT failiure if you permanently blanked off the egr valve.........eg. the emisions test would fail?

The answer to your question is 'No', it will not fail the emissions test on MoT.

I have just had my 133K '02 110 tested and the readings were the lowest they have ever been!

Testing for NOX is not a requirement of the MoT emissions test.

Peat

 

[pondweed]

that echoes what I found on several Rover 75 diesels....

 

[ukmarc]

The answer to your question is 'No', it will not fail the emissions test on MoT.

I have just had my 133K '02 110 tested and the readings were the lowest they have ever been!

Testing for NOX is not a requirement of the MoT emissions test.

Peat

I have just moted my 150000 multi in same condition with maf sensor unplugged and gave out 1.67 on meter acceptable is 3.00 whatever they measure it in well chuffed........plug maf sensor back in and its like a lazy slug

Marc

 

[pondweed]

has anyone done a comparison of mpg with MAF disconnected. My Rover comparisons - it was always less.

 

[Peat]

Not quite the same I know but I have recently replaced my MAF which has been in place since new 7 yrs ago, not because it was problematic simply had a brand new Bosch type I had bought last year when the EGR was playing up and thought it may be the cause but just cleaned the existing unit.

Anyway I fitted the new MAF at the same time I blanked the EGR last month and the MPG read-out is anywhere between 5 & 7 MPG better than before.

Does this count?

Peat

 

[martbass]

Why was my engine warning light staying on when the maf disconected?