When I started the car this morning the idle was all over the shop. I set off to see if things settled down and everything seemed fine for a while. A few miles from home I stopped at the top of a slip road and it stalled on me. It took a few attempts to get it to fire up again and when it did it was struggling to idle and generally wasnt running properly.

 

Managed to get to a layby and pulled over. The car would barely run at all on idle and if left for a while would eventually stall. If revved, it would splutter and then rev but would misfire quite loudly and would also boost up like it was under load. I checked for error codes and found none. Initially I thought it was the CTS so I plugged in to see what the ECU temp reading was and it said 81 against the dial indicated 90 so no major difference there. I also tried unplugging the CTS which made no difference.

 

Eventually I gaive up and called the breakdown which arrived promptly. He had a poke around under the bonnet and couldnt see anything obvious and asked me to start the engine. Amazingly it fired up and ran fine (typical), he followed me to a friends garage to make sure I had no issues and I didnt, it all ran fine. Spoke with my friend about what it could possibly be, coil pack etc, the usual stuff. Anyway, I decided I would set off home and see how it ran. Once again it ran like crap. I decided to unplug the MAF as an experiement and straight away it ran fine again.

 

Long and short of it is, it will not run with the MAF connected, but will with it disconnected. Now the MAF is only around 18 months old (genuine replacement purchased by myself), and I have checked all the boost hoses and intercooler hoses are tight and can find no issues. I am booking the car in for a smoke test to make sure its not a leak somewhere as my local garage seems to think this is the issue. But my train of thought is that if that was the case, surely it would not have all of a sudden run fine when the breakdown company came out?

 

Has anyone had this issue?, Is it likely to the be MAF? (dont wanna spend out on one uneccesarily), What else could it be?

 

Im a bit stuck at the moment as I need the car for work but dont have an endless pit of money to through at it.

 

Cheers

 

Dazz

Have you got access to any proper dedicated MAF cleaner? Would be the cheapest starting point, sensor could be contaminated. I would have thought with those kinds of consequences a split pipe would have thrown a code? Certainly sounds MAF related as disconnecting it made a major difference. Try borrow a MAF that's known to be working if you can find one suitable.

What air filter do you have? I've heard that sketchy brackets supplied with some aftermarket cai can disrupt the MAF through excessive vibration.

Thanks for the tips. I havent got access to any cleaner. A friend of mine has recently bought a new MAF for his so will try that and see what difference it makes.

 

I am running a CAI (was on the car when I bought it). the bracket that holds it in place has recently become detached and I havent had the chance to sort it with the weather being so crap. I wonder if the vibration has knackered the MAF sensor?

If you have access to VCDS have a look in engine measuring blocks & also do some data logging to see what the MAF is doing.

Unfortunately I only have access to VCDS Lite so dont think I can get into the right blocks. I will ask the garage that is doing the smoke test to check it as he has it. That is if we can keep the car running long enough with the MAF connected.

Thanks for the tips. I havent got access to any cleaner. A friend of mine has recently bought a new MAF for his so will try that and see what difference it makes.

 

I am running a CAI (was on the car when I bought it). the bracket that holds it in place has recently become detached and I havent had the chance to sort it with the weather being so crap. I wonder if the vibration has knackered the MAF sensor?

Don't think that will have helped, I read on some Seat forums of people having issues after fitting new kits. A detached bracket is worse than a fitted sketchy one as well I guess. If it is that I don't know if the MAF can be returned to good health. As said above a scan would prove useful to see how disrupted it is. You say that it ran fine following the recovery vehicle? Suggests it may not be totally screwed, try get the filter anchored properly see if it helps.

By the way I'd get your cai secured before you try your mates MAF

Will take a look and see it I can secure it. Cant have smoke test and logs done until tomorrow now as the garage I use cant fit me in this evening. Gonna leave car sat on drive until I can get this done as although the car runs ok with MAF unplugged, its just masking what ever is causing the issue so dont want to risk it.

I've had two maf sensors on my car now. The second one only lasted two years there about and mines all standard set up. They're not brilliant tbh. As for cleaning, me personally i wouldn't bother. I tried it and it didn't work it was knackered. Maybe worth a go i think theyre knocking on for £100 now but it didn't work for me.

A different car, but my Volvo 850 exhibited similar symptoms completely out of the blue just before Christmas with it not running with the MAF plugged in. I decided to bite the bullet and bought a new genuine Bosch one (not sure what the Skoda uses) and the car runs beautifully now

 

Trying your friends MAF sounds like a good bet A bit crap though if your current one only lasted 18 months...

If OEM ones are also a bit of a lottery and funds are low you could try a pattern one and save a bit, if you have to get one. You may get a good run out of it. I ran a pattern one in my Seat V5 for over a year, sold the car on still running sweet.

A faulty or even missing MAF will not prevent the engine from starting or running, so if yours only runs when it's disconnected then I can only assume the MAF is short circuited. This I would've thought would flag a fault code.

Mass air flow sensors deteriorate over time because they are bombarded with dust and dirt particles from the passing air. This is why it's so important that the air filter is clean and in top condition.

The MAF is a hot blade which is heated by a voltage supplied by the ECM. The passing air cools the blade, and the ECM determines the amount of air passing by how much it needs to supply the MAF to hear the blade again. The more passing air the higher the supply voltage is required. Cleaning the blade with a specialist cleaner will very often restore them to good working order. If yours is short circuit though the only place for it is the bin.

What is safe to use to clean them? Brake cleaner?

 

I replaced mine with a new one from Skoda nearly 3 years ago and it still seems fine (standard intake system), just asking for future reference.

I would Google MAF cleaner. Brake cleaner is a solvent and I wouldn't like to say whether or not it would damage the hot blade. I do know there are specialst cleaners that you can buy.

Try this.

http://www.mafcleaning.co.uk

Isopropal is generally excepted as the safest thing to use. I cleaned a working MAF with carb cleaner once & it died 2 days later

Thanks for the tips. I havent got access to any cleaner. A friend of mine has recently bought a new MAF for his so will try that and see what difference it makes.

 

I am running a CAI (was on the car when I bought it). the bracket that holds it in place has recently become detached and I havent had the chance to sort it with the weather being so crap. I wonder if the vibration has knackered the MAF sensor?

When I fitted a K&N cone filter to my previous Golf the intake piece holding the maf vibrated quite badly and killed it so yes - this could be the cause of your problems.  Once dead no amount of cleaning will revive it.

Try this.

http://www.mafcleaning.co.uk

 

I used the CRC stuff in the middle the other day, you have to use something MAF specific. As I said before and as others have said because of the unsecured cai it may be too late for the cleaner, but could be worth a pop, most important thing is get that cai secured before you try anything else.

Just a question for future reference. Is it worth taking the sensor apart to clean or is it just as good spraying the solution inside the unit? Really interested to know if anyone has actually cured a poor running maf by cleaning because most have said it never worked including myself.

I remove the sensor from the MAF housing & immerse it in a freezer bag with Isopropal in, giving a good shake for a few minutes, & let it dry out before refitting.

Just a question for future reference. Is it worth taking the sensor apart to clean or is it just as good spraying the solution inside the unit? Really interested to know if anyone has actually cured a poor running maf by cleaning because most have said it never worked including myself.

 

MIne was running ok, just gave it a clean as a course of maintenance as I had it out to modify the airbox and shove a big pipe in it.  I did it with it insitu, just gave it a squirt from either end and left to dry, idle seems a litle bit smoother, although it wasn't particularly lumpy.  Apparently my guy at my local garage brought his MAF in his big old bimmer back to health by giving it a squirt, I guess it depends what the problem is.  If its particles stuck to the blade/sensor it could work, but if blade has got marked or disrupted in some way it's probably unlikely. Got to be worth a try, nearly £10 a can mind, at least I've now got some in to try in future.

Dirt and dust coats the hot blade and so acts as an insulator. I explained how the MAF works earlier in this thread. If the hot blade is prevented from reacting to temperature changes then the ECM will not need to supply much to reheat it. The effect will be the ECM will think the engine is under low load conditions and will thus fuel the engine accordingly. No fault code will be stored because as far as the ECM is concerned there will be no fault. It has no way of knowing the MAF hot blade is covered in dirt.

People have a brain and can apply common sense and logic. Computers do not and cannot. Our failure to grasp that fact is one of the reasons why so many faults on modern cars are going misdiagnosed.

I remove the sensor from the MAF housing & immerse it in a freezer bag with Isopropal in, giving a good shake for a few minutes, & let it dry out before refitting.

That's how i did it last time but no joy. Bought the stuff from maplins iirc.

That's how i did it last time but no joy. Bought the stuff from maplins iirc.

Cleaning will never fix a goosed MAF, but it'll help a gunked up one.

So, today I decided take a look at the MAF as i'd got nothing to loose.

 

Disconnected everything, gave the MAF a damn good spray soaking with some MAF cleaner and left it in the house for a while whilst I secured the CAI nice and tight to the inner wing.

 

Refitted the MAF, plugged it in, cleared the codes and fired her up.......... Hey presto, one seriously smooth running car again with tons of power.

 

Im not saying its fixed it for good, but its certainly done the trick for now although I think im gonna put the standard airbox back on this weekend for the winter and monitor it and see how it goes.

 

Thanks for the helpful tips guys.