Cleaning/Replacing MAF Sensor

M

Micra Steve

I have a 2001 K11

I'm trying to remove my MAF sensor to give it a clean (with CNC cleaner), or if that doesn't do the trick, replace it - usual problem, poor idle etc

No problem undoing the screws - the former owner replaced the security ones with standard flat head screws - my question is how do you remove the connector attached to the MAF?

Do you just pull it off, or is there some kind of release catch?

I can't see anything to do except pull, but I'm pulling as hard as I can and it's not budging - and frankly, I'm getting a bit nervous about damaging the connector.
 
After reading through this website:

www.mafcleaning.co.uk

I saw that it states that you do not have to remove the sensor to clean it. All I did was remove the air filter and spray the CRC stuff through the mesh.
Did the job and car runs like a dream :)
 
alfantasti said:
After reading through this website:

www.mafcleaning.co.uk

I saw that it states that you do not have to remove the sensor to clean it. All I did was remove the air filter and spray the CRC stuff through the mesh.
Did the job and car runs like a dream :)
Click to expand...

Good to hear it worked for you.

Yes, I figured I'd try that as a last resort myself - although the website does seem to be recommending that you remove it to clean it, ideally.

But just in case cleaning it doesn't fix the problem and I have to fit a new one, I'd still be interested to know how you pull the connector off?

Anyone else out there struggled with this?
 
Connector seems to be like the one below.

The "tab" thing on the connector is quite hard to see because it's on the side facing away from me, but it feels like this - I've tried pressing down on the tab and sliding it forward, but nothing is moving.

Not sure if the tab has any function at all - maybe I just pull the connector off without doing anything?

I thought the hard thing would be getting the security screws off the MAF - not simply unplugging the connector!

main.jpg
 
If the connector hasn't been disturbed since new, then they tend to get slightly sticky to remove.
You could try spraying a small amount of silicone lubricant around the area where the connector slots into the sensor.
Don't use WD40, as the solvent in it will damage the plastic.

I should imagine it is a lock fit, so I wouldn't pull too hard without first figuring out how the tab lock works.
 
Managed to get a better look at the connector today by using a mirror - it looks the same, except the tab bit isn't as long as the one in the picture - it's about 3/4 the length.

Tried lifting, pressing, pushing, pulling the #@$% thing - nothing.

I've given up and squirted a couple of shots of CNC through the mesh at the bottom of the air box - haven't taken the car anywhere yet, so no idea if it's worked.

If it works, great - but even if it does, I'm sure I'll need to replace it one day, so the problem remains.

I've got 2 brand new MAF sensors (cheap ebay jobs) given to me by the former owner for spares - very useful if I can ever actually fit them!
 
Managed to get the connector off today and decided to start by swapping the MAF for a spare one, rather than clean the existing one - as I can just about drive the car with the existing MAF, so I don't want to mess with it.

The new MAF was no better - slightly worse in fact.

When you put a very slight pressure on the accelerator, the revs immediately drop - you have to press harder to get a good amount of revs going and stop it cutting out.

If you leave it just idling, with no throttle, it cuts out after a few seconds - but only once the engine is warm - when it first starts from cold it is fine.

I shall take the new MAF out tonight and give it a good clean with CNC - see if that helps.

I didn't clean it before putting it in, otherwise I wouldn't know if it was the cleaner solving the problem, or the new sensor - assuming it WILL solve the problem!
 
frank said:
Have you tried driving it with the maf disconnected steve ?
Click to expand...

No - I remember reading this will tell you if it IS the MAF at fault, and not something else going on - I'll try it later, before cleaning my new MAF

I presume you leave the MAF in place - and just take the connector off?
 
I had slightly poor running issues on my 1.4 K11C last week and previous weeks. Last week it stalled coming to a red light and again at the next one. I unplugged it and all was well. It obviously used a bit more fuel whilst it was unplugged but it was much better and wasn't stalling. It actually felt pretty fast.

I ordered this part number from GSF. I went through the Birmingham branch and had it mail ordered. It cost £120 all in for a Bremi one.

I used this part number:
ImageUploadedByTapatalk1429211334.944148.jpg
 
The Bosch part number that is. Don't waste your time, money or effort using a £25 MAF. It won't last and would likely have issues from the offset.
 
Well, I've just tried running it with the MAF disconnected and there is no improvement - if anything it was slightly worse.

I'll try giving the MAF a good clean with CNC (and connecting it back up obviously) - and see if that helps.

But if it runs the same when disconnected, am I right in thinking it CAN'T be the MAF causing the problem?

I've suspected a vacuum leak because I also get a very slight "whistling" type noise when driving - but there are no obvious signs of perished/split hoses etc - and if you listen to the engine when ticking over you can't hear a whistling sound - you only hear it when driving along (it seems to get a little louder the faster you go)
 
Gave the "new" MAF a clean and no improvement - but I wasn't expecting any, after disconnecting the MAF entirely failed to cure it.

I'm thinking it probably isn't the MAF at all now.

I don't have any of the other symptoms, such as poor performance, engine flat spots or kangarooing etc - the only problem I have is very low revs at idle when warm (revs are fine when cold), causing it to stall.

Is it possible to simply adjust the base idle speed up a touch on these coilpack K11's?

If so, I reckon that will fix things.
 
davyboy said:
Try taking your throttle position switch off. See what happens, fixed my poor idle, runs fine without it.
Click to expand...

Yes, I was planning to try that, but only for diagnostic reasons - ie, disconnect the TPS simply to see if it cures the problem - if it does, then clean or replace the TPS.

Can you just drive with the TPS permanently disconnected? It must be performing some useful function.
 
Yes you can drive without it connected, been doing it for a few months now, drives fine.
Occasionally the idle drops a bit but that's very occasionally, nothing to write home about.
 
After doing a lot of research, it seems most likely to be a problem with the Idle Air Control valve - hopefully it can be resolved simply by cleaning it.

I'm thinking this, as my problem is only with a low idle when warm - I don't have flat spots or performance issues associated with MAF sensors.

davyboy - It could be that disconnecting the TPS helps to indirectly fix the problem of a dirty IAC valve - not sure exactly how they work in relation to each other.

Anyway, my spark plugs are overdue for a change, so I'll start by doing that - as I've heard that Bosch plugs are better for coilpack K11's and can make a big difference to poor idle problems.

If that doesn't do the trick, I'll get the TPS and IAC valve off and give both of them a clean.

But I'm pretty sure it isn't the MAF - as I said earlier, I've tried disconnecting it and it made no difference, so I'm assuming that means the problem CAN'T lie there?
 
I think you'd have to remove the entire throttle body to do it - which is a slightly bigger job than a bumbling amateur like me would prefer to take on.
 
Disconnected the TPS today as an experiment - no improvement - possibly a bit worse.

Does this mean that the TPS can't be to blame either?

I was planning to remove the TPS and give it a clean (once I'd acquired the necessary tool) - and I'm curious to know if there is any point in trying it now?

Of course, it won't hurt anything to give it a clean, even if it's not to blame - all part of a general service - but at the moment, I'm more interested in solving my idle problem.
 
davyboy said:
Sounds more and more to me you need a new throttle body.
Click to expand...

Never really understood this throttle body business - doesn't replacing the individual sensors have the same effect as replacing the entire TB?

The TB itself is just a casting - it's the sensors in the TB that are performing the functions.
 
I think so. Only problems you can actually have with the tb is physical damage like bad mating surface to the inlet or butterfly is broken etc. Id check the iac
 
infinity said:
I think so. Only problems you can actually have with the tb is physical damage like bad mating surface to the inlet or butterfly is broken etc. Id check the iac
Click to expand...

Yes, I'd certainly check the IAC valve - I don't think there is much chance a new TB would solve anything, if I have already cleaned/replaced the individual sensors with no effect.

But I'm still unsure if I can 100% rule out the MAF and TPS - having disconnected both, with no improvement.
 
Update:

Just got an OBD2 scanner - and it's showing me running rich, with a long term fuel trim of around -15%

It was also showing P0100, P0110 and P0120 codes - all relating to the MAF and TPS - but as I have recently disconnected the MAF and TPS as part of the diagnostic process, I can't really go on that - it's possible that the codes could have been thrown simply by disconnecting them.

I think I'm right that running rich could be related to a faulty O2 sensor?

I've another reason to suspect this - the previous owner replaced the O2 sensor just before I bought it, so it could be an ongoing issue.

Any suggestions on ways to check if the O2 sensor is causing my low idle when warm? Apart from the obvious, fit a new one and see!
 
frank said:
you can monitor the lambda,s with a volt meter steve (or else a data lead and software)
Click to expand...

Yes, I've got a multimeter, so I can take some readings on the O2 sensor - just not sure how to go about it, what values I'm looking for and what it'll tell me.

Bottom line - any way of knowing for sure that the sensor is duff, before I spring for a new one?
 
infinity said:
You should disconnect your battery for two hours or so and that way clean the error codes.
Click to expand...

I cleaned the error codes with the scanner. Same thing I think - but clearing the codes isn't going to fix the problem.

I didn't have a fault code showing for the O2 sensor - but that doesn't mean there isn't a problem, it could be just below the threshold for triggering a code.

I've discovered that my scanner has an O2 test, so that will be easier than using a voltmeter - I'll get some results posted when I figure it out.

But can I also test the O2 sensor by simply disconnecting it - ie, if it runs fine when disconnected, does that mean the sensor is definately faulty?

Also, I believe the front and rear sensors are the same, so could I try switching them over?

I think the rear sensor is just for monitoring the CAT, so presumably the car would run fine with a faulty rear O2 sensor?
 
Fuel figures are fine ? The readings are close to a fail on MOT but has passed each time so far.
Don't know if there is a difference between the two bud.
 
Hi Serkan

Are you still having problems with your idle and rough running? I've been working on mine since I last posted on your thread and it's a lot better now. I'll put an update and talk you through what I did on your post 'idle rev'.
 
I cleaned my TB system in the weekend, because I had rough idle at startup, sometimes stalling. After the clean it seemed that it is working fine, but today in the morning the engine was stalling again, only after the third start could hold the idle, after warming it up the idle was rough. I took off the MAF connector, and the idle was stable after. When I am connecting back, the engine dies. Is it worth trying to unmount the MAF and clean it again, or should I change it? Before I had the P0171 error, system too lean. 1.0 facelift, coilpack.
Thank you.
 

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