Mk2 Tdci Idle Rough And General Hesitation After Maf Replaced

[daveyboy123]

hi all,

hope someone is able to assist me.

i recently had a MOT and service done on my 1.6 TDCI Focus. when it went to have work done the engine was running fine. there was an engine management light which i knew about as this was MAF Sensor problem but engine was fine, idle fine etc.

after service, MAF sensor replacement and MOT (which passed with no problems) the car now idles ver rough, usually takes about a min from starting the engine then the car sounds as though its going to stall, very shaky etc. Rev counter isn't going up or down though, staying at usual 750rpm.

once engine is hot, the shaky, rough idle doesn't seem to be as evident.

i also now get what seems like flat spots occasionally when accelarating and also sometimes if just in 3rd or 4th gear at a constant speed the car will now start shaking a bit and isn't smooth.

none of these problems were there before service and sensor replacement.

i explained all of this to mechanic as i also noticed when cold there seems to be small amounts of white smoke accompanied by a burning smell coming from engine bay (turbo area)when cold. as he was also doing my timing belt and water pump, he said he'd check it all over before returning it to me.

well problem still evident and he's had a look and can't find any problems.

whats causing it? is it the new sensor? i read that the batterey should be disconnected when fitting new sensor but doesn't appear this was done.

is the car on its last legs?

[jeebowhite]

i would suggest taking the car back to the garage it was serviced and MOT'd

[daveyboy123]

Yes I did, as above I took it back to the mechanic and he checked it all over again but couldn't find any problem and said that the engine is not the best as they constant have things go wrong.

I'm at a loss now, could it be the new maf sensor that's causing this?

[jeebowhite]

I recall someone displaying similar symptoms, he had the oil and filter changed again and it seemed to resolve the problem for him, it could be a similar issue.

[daveyboy123]

I spoke with mechanic today and he said to unplug maf sensor plug and run it without it for a couple of days to see if there is any change.

I unplugged and started car from cold and let it idle for 5 - 10 mins and car sounded much healthier as in it didn't sound like it was about to stall.

He said it is possible the sensor could be a faulty part

[jeebowhite]

Could indeed be the culprit

[daveyboy123]

Part used was a lucas maf, he did say pattern parts can be a bit hit and miss when it comes to sensors so advised I run car a bit over weekend with maf disconnected and see if it's problems I've had have vanished. If so he said he'll replace with genuine Ford part instead which is going to be a bit more bit of it sorts it then that's the main thing

[jeebowhite]

yeah like for like on sensors is best. the tolerances are so small in the differences that a perfectly good pattern part can still come bac kwrong.

Fingers crossed the sensor can get a refund (heck take a video, record the errors, and then if the replacement genuine works, take the part back for a refund showing them the evidence that its faulty!

[daveyboy123]

I did wonder at the start if it would be this part as the only other work I had done was usual service so air filter, oil etc and mot. Never had a problem before until maf was changed as it was throwing CEL.

Weird thing is the new sensor isn't making any lights come up on dash, not sure why that would be.

Mechanic said to just check over weekend to see if the problems I have had go with the maf disconnected then if they do he'll take part back and get refund and get genuine part and just charge me the difference, hopefully won't be too much more.

Is running without maf not going to cause other problems though?

[jeebowhite]

it will cause more smoking and the car will feel underpowered as the air fuel ratio is way out of proportion as the car reverts to using a standard amount of air in the combustion cycle, rather than using the MAF to adapt the right air fuel ration. when you boot it, the EML will come on as the car panics but it will be fine.

[daveyboy123]

Ok, I guess I'll still be able to tell if the general judder and hesitation etc are gone though so I'll give it a go and fingers crossed it's just a faulty sensor

Thank you for your help

[jeebowhite]

No worries matey let us know how you get on with it.

[daveyboy123]

Will do, drove car around todday without maf, car idled much better and no hesitation/random flat spots.

Only problem original Ford parts are over 200 which is more than double the one put in. Think he wants to try another make first before going down the expensive route.

Is it safe to run without maf for a while? Not getting smoke or anything, sounds basically like it should do. Engine management light is now on though.

I'm worried that after changing maf it's not going to fix it, is there anything else that could cause it or the fact it's running better without it connected would that indicate sensor is def at fault?

[jeebowhite]

I wouldn't think it's a problem but it's just not best for the car lol as for the part, go used maybe?

[daveyboy123]

Just one more thing, would the new sensor work straight away correctly. I read somewhere that sometime the ecu will take a bit of driving to correct everything and it to run smooth. If that's the case could the sensor I have be ok but just needs running in a bit or would you change it to be on safe side?

[jeebowhite]

Easiest answer is to disconnect the battery whilst it's replaced. That way it needs no adjustment as it just goes back to factory settings

[daveyboy123]

Ok, well part was replaced and seems much better. Idle seems normal now and isn't struggling anymore. So looks like it's sorted :)

Thanks for the help.

[jeebowhite]

Glad it's sorted did you go like for like or pattern part

[daveyboy123]

It was another pattern part, slightly more expensive by about £20, can't remember exact name but did sound like a German brand. Hopefully I'll have more luck with this one.