Mass Air flow problem?
Discussion
Hi all,
Had an ongoing problem that I was convinced was the throttle pot. After fitting the new pot though I find it isn't. My next course of attack is the mass air flow sensor. The symptoms are pretty much just bucking and hesitation under acceleration or load. It starts fine and seems to idle fine but as soon as you pull away problems start.
My plan is to take off the sensor and give it a good clean with contact cleaner and see what happens. Am I right in thinking the S has two sensors or does it just look like that? Any suggestions for how to tackle it or even whether or not I am barking up the wrong tree?
Thanks in advance
Pete
Had an ongoing problem that I was convinced was the throttle pot. After fitting the new pot though I find it isn't. My next course of attack is the mass air flow sensor. The symptoms are pretty much just bucking and hesitation under acceleration or load. It starts fine and seems to idle fine but as soon as you pull away problems start.
My plan is to take off the sensor and give it a good clean with contact cleaner and see what happens. Am I right in thinking the S has two sensors or does it just look like that? Any suggestions for how to tackle it or even whether or not I am barking up the wrong tree?
Thanks in advance
Pete
Yes there are two sensors, one for air temp and the other for air flow IIRC (?)
alo look for leaks in the flexi pipe as well as leaks between the plenum and the Brake Servo...
might be worth checking this out too...
http://www.fordscorpio.co.uk/faultfinds.htm
good luck
k
alo look for leaks in the flexi pipe as well as leaks between the plenum and the Brake Servo...
might be worth checking this out too...
http://www.fordscorpio.co.uk/faultfinds.htm
good luck
k
May I suggest you also check the engine loom multiplug that sits in the V to the right side. On mine it's under the ignition coil. Wiring for various engine sensors and ISCV pass through it. I get these type of symptoms anually (ONCE A YEAR before I get any smart comments 
). Generally I just separate the plug, give it a squirt with WD40 or similar then plug and unplug a couple of times. Seems to cure it for a year or so.
Gotta be worth a try
Carl.
). Generally I just separate the plug, give it a squirt with WD40 or similar then plug and unplug a couple of times. Seems to cure it for a year or so.Gotta be worth a try
Carl.
Ceejay73 said:
May I suggest you also check the engine loom multiplug that sits in the V to the right side. On mine it's under the ignition coil. Wiring for various engine sensors and ISCV pass through it. I get these type of symptoms anually (ONCE A YEAR before I get any smart comments ). Generally I just separate the plug, give it a squirt with WD40 or similar then plug and unplug a couple of times. Seems to cure it for a year or so.
Gotta be worth a try
Carl.
Gotta be worth a try for ease. Thanks.). Generally I just separate the plug, give it a squirt with WD40 or similar then plug and unplug a couple of times. Seems to cure it for a year or so.Gotta be worth a try
Carl.
Road2Ruin said:
What sort of symptoms were you getting?
From memory, running very rich and lumpy on idle seemed the most pronounced. Throttle pot was confirmed as not being at fault.The inside of the MAF was very mucky but cleaned up well using contact / carb cleaner and a cotton bud.
The result - much steadier tickover, exhaust fumes were far less 'rich' and a smoother progression through the rev range.
Ceejay73 said:
May I suggest you also check the engine loom multiplug that sits in the V to the right side. On mine it's under the ignition coil. Wiring for various engine sensors and ISCV pass through it. I get these type of symptoms anually (ONCE A YEAR before I get any smart comments ). Generally I just separate the plug, give it a squirt with WD40 or similar then plug and unplug a couple of times. Seems to cure it for a year or so.
Gotta be worth a try
Carl.
Also check the dreaded yellow connector on the left hand side of the steering column, if you still have it. When mine was missing on accelaration due to a burnt yellow connector, eventually started stalling at junctions and had to waggle the loom to get going again. Had similar again with a leaking vacumm hose to the servo but this also gave me a random tickover.). Generally I just separate the plug, give it a squirt with WD40 or similar then plug and unplug a couple of times. Seems to cure it for a year or so.Gotta be worth a try
Carl.
Rob.
Thanks. I don't think I have the yellow connector. I had a look when I removed the dash a while back as had to remove stearing column cowl at same time. Wasn't sure where to look but nothing obvious. So far today I have removed MAF and connectors and cleaned all. Wasn't brave enough to use cotton buds but very greasy inside. also bungged a load of carb cleaner into butterfly assembly and removed multi connector and cleaned. Will now wait til it's dry and take it out! Started ok anyway, but that has never been a problem. doh.
I don't suppose you have access to an oscilloscope?
The flap inside the airflow meter that moves moves a variable resistor, its a contact on a carbon track and if its worn it will give spurious voltages as it moves. If you put a scope on the voltage output and moded the flap you would see the noisy ouytput on the screen, you may be able to see it to some extent with a meter.
The flap inside the airflow meter that moves moves a variable resistor, its a contact on a carbon track and if its worn it will give spurious voltages as it moves. If you put a scope on the voltage output and moded the flap you would see the noisy ouytput on the screen, you may be able to see it to some extent with a meter.
Barkychoc said:
I don't suppose you have access to an oscilloscope?
The flap inside the airflow meter that moves moves a variable resistor, its a contact on a carbon track and if its worn it will give spurious voltages as it moves. If you put a scope on the voltage output and moded the flap you would see the noisy ouytput on the screen, you may be able to see it to some extent with a meter.
Sadly not. Will see what happens and if still no joy will give it a blast with carb cleaner then contact cleaner. Very easy to get off and on though.The flap inside the airflow meter that moves moves a variable resistor, its a contact on a carbon track and if its worn it will give spurious voltages as it moves. If you put a scope on the voltage output and moded the flap you would see the noisy ouytput on the screen, you may be able to see it to some extent with a meter.
I think they are pretty simple and unless you have done inter-galactic miles the sensor track should not be worn out. I reckon a good clean of the contacts, and as said above use carb cleaner and cotton buds to clean the sensor wire that hides behind a plastic shroud in the airflow.
Do you still have the manky pipe running from the rocker box breather tothe airfilter ? the one that dumps oily mist into the airflow upstream of the sensors ? all in a vain attempt to save the planet
if so have a think about replacing it with a small filter on the breather cap itself.
you should also check out the Rats Nest under the glove box and make sure you dont have any damp or corrosion problems on the various connectors, ECU and relays tucked (or stuffed) in there.
good luck
K
Do you still have the manky pipe running from the rocker box breather tothe airfilter ? the one that dumps oily mist into the airflow upstream of the sensors ? all in a vain attempt to save the planet
if so have a think about replacing it with a small filter on the breather cap itself.you should also check out the Rats Nest under the glove box and make sure you dont have any damp or corrosion problems on the various connectors, ECU and relays tucked (or stuffed) in there.
good luck
K
Sadly cleaning the mass airflow sensoe has not cured the problem. Not sure where to look now! I have noticed it's starting to act funny at tickover, which it didn't do before. Still though the main symptoms are bucking, lots of pops and bangs from exhaust and a real problem accelerating. I may take ti round to the local mechaninc and get him to stick it on the computer for the sake of £30 and see what he says. Do most garages have the software to read that for ECU?
Road2Ruin said:
lots of pops and bangs from exhaust
Ah now I don't think you mentioned this before.Are there really lots of pops and bangs and are they coming when you try to accelerate or on overrun?
Are the symptoms apparent when you try to rev the car in neutral or only under load?
Carl.
Ceejay73 said:
Ah now I don't think you mentioned this before.
Are there really lots of pops and bangs and are they coming when you try to accelerate or on overrun?
Are the symptoms apparent when you try to rev the car in neutral or only under load?
Carl.
Hi Carl,Are there really lots of pops and bangs and are they coming when you try to accelerate or on overrun?
Are the symptoms apparent when you try to rev the car in neutral or only under load?
Carl.
No just on the acceleration thing. I originally put this down to an over rich mixture due to some ECU confusion. It's almost like the car cuts out for a second then kicks back into life followed by exhaust pops and bangs. It did do this the other day at idle as well though but that was the first time.
Pete
Could it be fuel delivery/pressure problems?
I had mine cutting out under acceleration (and going round left hand bends). Spent ages checking/cleaning/changing all the electrical stuff with no success. In the end borrowed a fuel pressure test kit.
Managed to create the problem and the fuel pressure dropped to almost nothing.
We then found rust and other c**p in the fuel tank. Also check the little in line filter in the bottom of the tank pick-up.
Filter Before Cleaning:
Filter After Cleaning :
I had mine cutting out under acceleration (and going round left hand bends). Spent ages checking/cleaning/changing all the electrical stuff with no success. In the end borrowed a fuel pressure test kit.
Managed to create the problem and the fuel pressure dropped to almost nothing.
We then found rust and other c**p in the fuel tank. Also check the little in line filter in the bottom of the tank pick-up.
Filter Before Cleaning:
Filter After Cleaning :
Ok, does it only do it when driving or will it do it if you try to rev it with the car out of gear?
When it pops and bangs, do you just get one bang and then it goes or is it like a machine gun and no power?
Does it get worse as the engine gets hotter?
Sorry for all the Q's.
I am thinking maybe the ignition timing is wandering. If it is burning fuel in the exhaust (causing the pops and bangs) then that suggests it is firing the plugs whilst a valve is open. Just trying to get my head around it.
Carl.
When it pops and bangs, do you just get one bang and then it goes or is it like a machine gun and no power?
Does it get worse as the engine gets hotter?
Sorry for all the Q's.
I am thinking maybe the ignition timing is wandering. If it is burning fuel in the exhaust (causing the pops and bangs) then that suggests it is firing the plugs whilst a valve is open. Just trying to get my head around it.
Carl.
To answer both queries,
Yes I did consider the fuel preesure issue myself but wasn't sure how or what to check. Fuel pump, pressure regulator or something else? With regards to the poping, it tends just to be one pop each cut out, but because under hard acceleration it cuts out every second or two, it's doing it all the time. I will check the filter but it's not done that many miles since the last service....if they changed the filter that is....
Yes I did consider the fuel preesure issue myself but wasn't sure how or what to check. Fuel pump, pressure regulator or something else? With regards to the poping, it tends just to be one pop each cut out, but because under hard acceleration it cuts out every second or two, it's doing it all the time. I will check the filter but it's not done that many miles since the last service....if they changed the filter that is....
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