Technical Driving with Air Mass Sensor unplugged- how damaging?

[Will S]

Hi Fiat people.. We have a 2012 Fiat Ducato 3.0 litre 160 bhp 6 speed. Maxi XLWB with a very chequered history! It’s a campervan conversion. Without going into too much history, we are unable to resolve the age old EGR engine management fault code. The garage has been through the motions of cleaning the EGR valve and cooler, inspecting and trialling replacement throttle position valves and map sensor, air mass sensor and most recently replacing the EGR valve. Nothing has worked. The Fiat main dealer (Adam Morey in Southampton) put it through their diagnostics and stated it had an electrical fault which is highly probable as it’s had a replacement engine (unknown source or installer). Anyhow, the only way it will currently drive is with the Air mass sensor unplugged. With it plugged in the EGR fault code is still present and it revs intermittently, sometimes lethargically other times not at all and for a few minutes fine!? So, my question is what is the impact of driving with the Air Mass sensor unplugged? Short term it runs ok, may be a little high on the MPG, but what would be the long term impact?
We have exhausted the options to repair the issues and have well overspent on garage fees so are now at the point we want to use it before selling it on. Any thoughts on what the impact would be driving it for short local journeys (under 100 miles) and one long journey to Spain with the Air Mass unplugged?

 

[bugsymike]

Hi Fiat people.. We have a 2012 Fiat Ducato 3.0 litre 160 bhp 6 speed. Maxi XLWB with a very chequered history! It’s a campervan conversion. Without going into too much history, we are unable to resolve the age old EGR engine management fault code. The garage has been through the motions of cleaning the EGR valve and cooler, inspecting and trialling replacement throttle position valves and map sensor, air mass sensor and most recently replacing the EGR valve. Nothing has worked. The Fiat main dealer (Adam Morey in Southampton) put it through their diagnostics and stated it had an electrical fault which is highly probable as it’s had a replacement engine (unknown source or installer). Anyhow, the only way it will currently drive is with the Air mass sensor unplugged. With it plugged in the EGR fault code is still present and it revs intermittently, sometimes lethargically other times not at all and for a few minutes fine!? So, my question is what is the impact of driving with the Air Mass sensor unplugged? Short term it runs ok, may be a little high on the MPG, but what would be the long term impact?
We have exhausted the options to repair the issues and have well overspent on garage fees so are now at the point we want to use it before selling it on. Any thoughts on what the impact would be driving it for short local journeys (under 100 miles) and one long journey to Spain with the Air Mass unplugged?

I think you will find the ECU is just using it's simple "base settings" designed as a get you home method when sensor fails, which is why it runs better with it unplugged.
As you have found it does affect fuel economy and you may have issues at MOT time.
Long term I suspect if it is using more fuel then the exhaust will clog up quicker, including EGR and DPF if applicable.
I bought a Fiat Doblo 1.9 with the MAF unplugged, previous owner had tried new sensors etc. In the end on that one, I found the fault was broken wires a few inches from the plug but withing their plastic sheathing.
Whilst Fiat Dealer computers are very good, in some cases a good specialist vehicle diagnostics company can locate a fault with just a couple of hours of labour. We have one down our way that the trade uses when they give up themselves.

 

[Communicator]

I think you will find the ECU is just using it's simple "base settings" designed as a get you home method when sensor fails, which is why it runs better with it unplugged.
As you have found it does affect fuel economy and you may have issues at MOT time.
Long term I suspect if it is using more fuel then the exhaust will clog up quicker, including EGR and DPF if applicable.
I bought a Fiat Doblo 1.9 with the MAF unplugged, previous owner had tried new sensors etc. In the end on that one, I found the fault was broken wires a few inches from the plug but withing their plastic sheathing.
Whilst Fiat Dealer computers are very good, in some cases a good specialist vehicle diagnostics company can locate a fault with just a couple of hours of labour. We have one down our way that the trade uses when they give up themselves.

Broken wires are not easy to localise, but I have been considering the purchase of a telecommunications style cable tracer. This could possibly be of use on vehicles, as well as on our domestic telephone, and ethernet cabling, both of which are much above average in extent.

 

[bugsymike]

Broken wires are not easy to localise, but I have been considering the purchase of a telecommunications style cable tracer. This could possibly be of use on vehicles, as well as on our domestic telephone, and ethernet cabling, both of which are much above average in extent.

I have used these with varying success. probably down to the lack of a skilled operator.

 

[Ocwobio]

Broken wires are not easy to localise, but I have been considering the purchase of a telecommunications style cable tracer. This could possibly be of use on vehicles, as well as on our domestic telephone, and ethernet cabling, both of which are much above average in extent.

Indeed. I bought one from ebay a while ago. I had no immediate use for it, but I'm sure it will get used one day. My only concern is potential coupling of the signal in tight situations. But it could help the OP as it does sound like a bad connection issue, and many places do not like chasing those- I can't say I blame them with modern vehicles!

 

[porta]

Indeed. I bought one from ebay a while ago. I had no immediate use for it, but I'm sure it will get used one day. My only concern is potential coupling of the signal in tight situations. But it could help the OP as it does sound like a bad connection issue, and many places do not like chasing those- I can't say I blame them with modern vehicles!

Yup, modern vehicles are a complete pain to find broken wires

 

[Will S]

I think you will find the ECU is just using it's simple "base settings" designed as a get you home method when sensor fails, which is why it runs better with it unplugged.
As you have found it does affect fuel economy and you may have issues at MOT time.
Long term I suspect if it is using more fuel then the exhaust will clog up quicker, including EGR and DPF if applicable.
I bought a Fiat Doblo 1.9 with the MAF unplugged, previous owner had tried new sensors etc. In the end on that one, I found the fault was broken wires a few inches from the plug but withing their plastic sheathing.
Whilst Fiat Dealer computers are very good, in some cases a good specialist vehicle diagnostics company can locate a fault with just a couple of hours of labour. We have one down our way that the trade uses when they give up themselves.

I think you will find the ECU is just using it's simple "base settings" designed as a get you home method when sensor fails, which is why it runs better with it unplugged.
As you have found it does affect fuel economy and you may have issues at MOT time.
Long term I suspect if it is using more fuel then the exhaust will clog up quicker, including EGR and DPF if applicable.
I bought a Fiat Doblo 1.9 with the MAF unplugged, previous owner had tried new sensors etc. In the end on that one, I found the fault was broken wires a few inches from the plug but withing their plastic sheathing.
Whilst Fiat Dealer computers are very good, in some cases a good specialist vehicle diagnostics company can locate a fault with just a couple of hours of labour. We have one down our way that the trade uses when they give up themselves.

Ok thanks BugsyMike.. we’ll look into a specialist vehicle diagnostic outfit in the south.. Any other thoughts/ comments on impact of driving with air mass sensor turned off would be appreciated?

 

[bugsymike]

Ok thanks BugsyMike.. we’ll look into a specialist vehicle diagnostic outfit in the south.. Any other thoughts/ comments on impact of driving with air mass sensor turned off would be appreciated?

Basically it is there for a reason and needs to work properly for efficient running of engine. So ideally "short term" only disconnect.

 

[Communicator]

My x244 does not have EGR, and neither does it have a MAF sensor, versions with EGR do have the MAF sensor fitted. The description in Fiat eLearn for the EGR system specifically mentions the MAF sensor. I believe that the MAF sensor is essential for operation of the EGR system.

Looking a the x250 Fiat Training Manual for the 3.0 litre engine, the desription of the EGR system does not mention the MAF sensor. See attached extract. I believe the mention of a Water Pressure Sensor to be a gross error, and should read Mass Airflow Sensor, or other appropriate name.

Conclusion is that the EGR system will be inoperable in the MAF is disconnected. Apparently this will increase NOx emmissions, but with the engine running incorrectly what will happen to the carbon (soot) in the exhaust. The 3.0 litre has a catalytic converter, These are expensive and I would not recommend risking damage to it.

Given that the vehicle is an x250, it could be suffering from the "rusty junction" problem where the wiring harness close to the engine control unit (ECU) abraids against tubular section of framework below the LHS headlight, which must be removed for inspection. This is a possible cause of the wiring fault, which can be eliminated without special equipment.

The photo originally posted by @Reg 65 and he may wish to comment.