1.6 petrol - knocking/popping sound & V rough cold start (with video)

[kevinb6]

Since Sunday my '02 A4 B6 1.6 petrol has developed a problem when starting. The engine runs very roughly, revs rise and fall, stalls if you try to drive.

There is also a metallic poping sound (like hail stones hitting a metal roof perhaps). I made a short video, the sound occurs about 3 times within 25 sec.



Once I wait 5 min to warm it up it drives as normal.

Background:

Engine light has been on for about a year, got error codes checked. guy said it was 2 x MAFs, expensive repair considering age/ value of car and to leave as is as driving OK. Could this be the cause? Of course there may be new codes there now but have no way to read.

Thanks!

[calum]

Since Sunday my '02 A4 B6 1.6 petrol has developed a problem when starting. The engine runs very roughly, revs rise and fall, stalls if you try to drive.

There is also a metallic poping sound (like hail stones hitting a metal roof perhaps). I made a short video, the sound occurs about 3 times within 25 sec.



Once I wait 5 min to warm it up it drives as normal.

Background:

Engine light has been on for about a year, got error codes checked. guy said it was 2 x MAFs, expensive repair considering age/ value of car and to leave as is as driving OK. Could this be the cause? Of course there may be new codes there now but have no way to read.

Thanks!

What phone do you have? Plenty of free apps on android or paid apps on iPhone that will allow you to read and clear fault codes. Does sound like a fuelling issue though. All you need is a blue tooth dongle for the obd11 port or you will need a specific one for I phone. Banging noise could be the catalytic converter thanks to the guy who advised you not to fix the fault.

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[kevinb6]

Thanks. I have both types of phone/tablet. Can you recommenced a dongle/app please?

Is the cat not near the back, or is it near the engine bay, which is where the sound is coming from?

[Rob69]

get a compression test done to check for burnt out exhaust valve

[Crasher]

The cat is right up as close to the manifold as possible, poor running wrecks them. You can't get away with driving with the light on forever now as it is an MOT failure. What was he on about with 2xMAF's, there is only one and they are not very expensive.

[kevinb6]

Thanks, it could be the cat then it it's in that area - I'll try to see if I can find the source of the noise.

I'm in Ireland - a light will not fail out NCT test, as long as emissions etc are ok.

Sorry thought there were 2 air flow sensors Attention Required! | Cloudflare

[calum]

Thanks, it could be the cat then it it's in that area - I'll try to see if I can find the source of the noise.

I'm in Ireland - a light will not fail out NCT test, as long as emissions etc are ok.

Sorry thought there were 2 air flow sensors Attention Required! | Cloudflare

I can't see it passing emissions with a knackered cat. The reason it is knackered is because of the poor advice you were given. It usually overheats and breaks or it can even melt, both leave the monolith rattling around in the converters casing.
His advice now means you need a replacement cat as well as a MAF.

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[kevinb6]

I can't see it passing emissions with a knackered cat. The reason it is knackered is because of the poor advice you were given. It usually overheats and breaks or it can even melt, both leave the monolith rattling around in the converters casing.
His advice now means you need a replacement cat as well as a MAF.

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Hi are we sure it's the cat though, would it make that sound and be ok once it's warmed up?

Re your earlier post about a dongle/app, what would be a good one that would help me fix this issue? Thanks for your help!

[Crasher]

I'm in Ireland - a light will not fail out NCT test, as long as emissions etc are ok.

Right, I see, so the UK implements the new EU regulations on annual vehicle safety checks but other countries staying in the EU ignore them, and people wonder why half of the UK voted to get out, NOT I hasten to add including me....

[calum]

Hi are we sure it's the cat though, would it make that sound and be ok once it's warmed up?

Re your earlier post about a dongle/app, what would be a good one that would help me fix this issue? Thanks for your help!

I have vcds on the laptop so you'll just have to try them out.
Pretty sure that the banging is the cat monolith. There's only one way to find out though.

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