Omega Owners Forum

Omega Help Area => Omega General Help => Topic started by: LC0112G on 24 July 2012, 22:35:11

Title: TC73 Mass Airflow Sensor Low
Post by: LC0112G on 24 July 2012, 22:35:11
Is the 'cure' for this replacement?

3.0L Facelift Auto Omega B Y reg. Story is. Been doing a lot of miles recently on the last day of the last trip, I noticed the EML pulsing rapidly (Mostly on but flickering off at about 2 pulses a second) whilst on light throttle. Give it a bit of wellie and the EML goes out, but it'll come on again when I get stuck behind Auntie Dorris doing 30MPH on a desestricted single carrageway.

I assumed lambda sensor, due to it pulsing on and off. And continued driving for the past week. Have noticed that it's Ok when cold, but after it's warm it'll normally come on at the first bit of coasting. Then more recent'y I've noticed a big flat spot on light acceleration out of idle. So starting to worry about CAT's and EGR's I finally got my backside in gear and did a blink test tonight. Got 12, 73 and 31 on a non running engine. Which suggests MAF sensor.

So do I simply go down the local stealer and order a new one tomorrow, and fit it at the weekend?

Cheers
Malcolm
Title: Re: TC73 Mass Airflow Sensor Low
Post by: dbug on 24 July 2012, 23:04:04
Try running with the MAF unplugged first to see if your symptoms go away ;)
If they do you need new MAF.
Title: Re: TC73 Mass Airflow Sensor Low
Post by: LC0112G on 24 July 2012, 23:21:29
Try running with the MAF unplugged first to see if your symptoms go away ;)
If they do you need new MAF.

Which symptom goes away? The EML or the flat spot? Can't see that the Engine managment is going to be overly impressed if I unplug one of it's sensors?
Title: Re: TC73 Mass Airflow Sensor Low
Post by: dbug on 25 July 2012, 00:57:38
Try running with the MAF unplugged first to see if your symptoms go away ;)
If they do you need new MAF.

Which symptom goes away? The EML or the flat spot? Can't see that the Engine managment is going to be overly impressed if I unplug one of it's sensors?

It will be impressed mate - it goes to a default map -  ;)
Rather than try diagnostics why not just follow your own suggestion and buy a new one - you never know it may solve your problem(s) - or it may not ::) ::)
Title: Re: TC73 Mass Airflow Sensor Low
Post by: LC0112G on 25 July 2012, 14:10:29
Try running with the MAF unplugged first to see if your symptoms go away ;)
If they do you need new MAF.

Which symptom goes away? The EML or the flat spot? Can't see that the Engine managment is going to be overly impressed if I unplug one of it's sensors?

It will be impressed mate - it goes to a default map -  ;)
Rather than try diagnostics why not just follow your own suggestion and buy a new one - you never know it may solve your problem(s) - or it may not ::) ::)

I wasn't questioning your idea - meerly asking if your fix was looking to shut the EML lamp off, or cure the flat spot.

I've just been down the dealers. New part is over £200, plus vat. So I'll unplug it on the way home tonight and see what happens ;D
Title: Re: TC73 Mass Airflow Sensor Low
Post by: TheBoy on 25 July 2012, 18:47:04
Unplugging will bring EML on, definately. But if it cures the underlying symptoms, then its a starter for 10 ;)


Crank sensor faults can originally show up as erroneous 73/74, so don't take the codes as gospel.
Title: Re: TC73 Mass Airflow Sensor Low
Post by: LC0112G on 25 July 2012, 21:52:21
Results were inconclusive.

Unplugged the sensor, and started the car. EML came on immediatley. Went tor a 20 minute drive, no further issues.

Stopped round the back of Yeovilton to pole off the Merlins on Olympic dury. Started the engine again, selected reverse, pressed the throttle and it stalled. Back to neutral, started, and everthing OK again. Then as I pulled away from the next junction a loss of acceleration for about a second, but after that everything OK.

So this weekend I'm going to clean the IACV, Check the auto box fluid level, fix the brake pad warning cause, and put some windscreen washer water in. All jobs that are long overdue. Then if the problems persist, eBay for a new MAF sensor.

How much warning of a Cam/Crank sensor failure do you get?

Cheers
Malcolm   
Title: Re: TC73 Mass Airflow Sensor Low
Post by: dbug on 25 July 2012, 22:03:58
Unplugging will bring EML on, definately. But if it cures the underlying symptoms, then its a starter for 10 ;)


Crank sensor faults can originally show up as erroneous 73/74, so don't take the codes as gospel.

When I had a duff MAF on my old Elite, ran for about a week whilst waiting for replacement MAF.  At no time did my EML light come on (except when ignition first switched on!).  Slight performance hit but otherwise ok.

My symptoms were car would fire up but immediately stalled if accelerator depressed.  Code 73 apparent.
Title: Re: TC73 Mass Airflow Sensor Low
Post by: noel on 25 July 2012, 22:16:56
Unplugging will bring EML on, definately. But if it cures the underlying symptoms, then its a starter for 10 ;)


Crank sensor faults can originally show up as erroneous 73/74, so don't take the codes as gospel.

When I had a duff MAF on my old Elite, ran for about a week whilst waiting for replacement MAF.  At no time did my EML light come on (except when ignition first switched on!).  Slight performance hit but otherwise ok.

My symptoms were car would fire up but immediately stalled if accelerator depressed.  Code 73 apparent.
same symptons as my 2.6, replaced with a genuine bosch maf and problem sorted :y
Title: Re: TC73 Mass Airflow Sensor Low
Post by: Darth Loo-knee on 25 July 2012, 23:10:10
Its strange as all the Omegas I have worked on or owned never really had a MAF problem until this MV6 estate I have now.......I was on the motorway when it decided to give up. EML came on, car still drove at motorway speed but MPG plummeted quickly. A little flat if I am honest too. Thing is I was over 200 miles from home and so I don't think it did either my CATs or exhaust any favours  :'(
What you need to remember is if the MAF is spent, the car will be thinking its running lean so puts more fuel in.... this is not good for MPG CATs or exhaust... ::)

I ended up changing my CATs and exhaust..

Just to add, dont go paying main Dealer prices.. Steve Omega Parts or one of the Breakers on here may have a good secondhand one, like I started to say quiet rare to go i my experience  :-*
Title: Re: TC73 Mass Airflow Sensor Low
Post by: RobG on 26 July 2012, 00:01:28
Its strange as all the Omegas I have worked on or owned never really had a MAF problem until this MV6 estate I have now.......I was on the motorway when it decided to give up. EML came on, car still drove at motorway speed but MPG plummeted quickly. A little flat if I am honest too. Thing is I was over 200 miles from home and so I don't think it did either my CATs or exhaust any favours  :'(
What you need to remember is if the MAF is spent, the car will be thinking its running lean so puts more fuel in.... this is not good for MPG CATs or exhaust... ::)

I ended up changing my CATs and exhaust..

Just to add, dont go paying main Dealer prices.. Steve Omega Parts or one of the Breakers on here may have a good secondhand one, like I started to say quiet rare to go i my experience  :-*
Op`s been offered one Daz :)
Title: Re: TC73 Mass Airflow Sensor Low
Post by: LC0112G on 26 July 2012, 00:24:08
EML came on immediatley and stayed on throughout the whole 20 minute test drive. It does flicker though - difficult to describe - kind of on 95% of the time, but flickering off perhaps twice a second. 'Course what I haven't done is re-check the blink codes to see if anything new is there  ::)

This is a relatively high milage car coming up to 200K. Engine was rebuilt at 90K due to a cam belt snap, but I doubt any of the sensors were changed at that time.

What you need to remember is if the MAF is spent, the car will be thinking its running lean so puts more fuel in.... this is not good for MPG CATs or exhaust... ::)

If that's true its a pretty crap EFI setup. I have no knowlege of the Omega system, but systems I am familiar with don't work like that. Yes they try to measure the amount of air going in (using MAP or MAF), and then calculate the fuel required depending on this and lots of other variables. But the lambda sensors then monitor the results of the combustion in the exhaust pipe, and tweak the fuelling up/down accordingly, particularly at low/medium throttle settings. Any fuelling errors large enough to cause cat damage would cause lambda sensor trouble codes first.

I would expect fuel consumption won't be the best, and driving thousands of miles like it won't do anything any good. But a few hundred miles on a motorway enough to werck a cat without any lambda sensor warning TC's?
Title: Re: TC73 Mass Airflow Sensor Low
Post by: Darth Loo-knee on 26 July 2012, 11:10:37
Its strange as all the Omegas I have worked on or owned never really had a MAF problem until this MV6 estate I have now.......I was on the motorway when it decided to give up. EML came on, car still drove at motorway speed but MPG plummeted quickly. A little flat if I am honest too. Thing is I was over 200 miles from home and so I don't think it did either my CATs or exhaust any favours  :'(
What you need to remember is if the MAF is spent, the car will be thinking its running lean so puts more fuel in.... this is not good for MPG CATs or exhaust... ::)

I ended up changing my CATs and exhaust..

Just to add, dont go paying main Dealer prices.. Steve Omega Parts or one of the Breakers on here may have a good secondhand one, like I started to say quiet rare to go i my experience  :-*
Op`s been offered one Daz :)

Sorry Rob, full of Jim Beam last night  ::)