Intake air leak? Hmmmmmm

[S3AMJ]

Hey everyone, so managed to gets lots done this weekend, which I’ll update my build thread soon. But here’s my question....

Finished my PCV simplification and started the car, runs for about 2-3 seconds and dies, check fuel, spark all seems fine. Then I decided to unplug the MAF. Car starts and runs perfectly! The MAF is relatively new and worked faultlessly before I did the PCV changes. I’m getting the code P0102. Suggests there might be a fault with wiring, MAF sensor or intake air leak? If I had an air leak, would it just stall the engine completely...... I’ve had an air leak before and the cars run rough, but never not started.

Any advice or suggestions?

Ash

 

[Stuart B]

The last person i recall who had this problem didn't block off the nipple on the bottom of the inlet manifold. This is supposed to have some tubing with a bolt in it. Not left open or connected into the vac lines of breather piping

 

[andrew_wright]

Hey everyone, so managed to gets lots done this weekend, which I’ll update my build thread soon. But here’s my question....

Finished my PCV simplification and started the car, runs for about 2-3 seconds and dies, check fuel, spark all seems fine. Then I decided to unplug the MAF. Car starts and runs perfectly! The MAF is relatively new and worked faultlessly before I did the PCV changes. I’m getting the code P0102. Suggests there might be a fault with wiring, MAF sensor or intake air leak? If I had an air leak, would it just stall the engine completely...... I’ve had an air leak before and the cars run rough, but never not started.

Any advice or suggestions?

Ash

At a guess I'd say wiring issue, plug it back in and give the wire a "wiggle" and see.

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[S3AMJ]

The last person i recall who had this problem didn't block off the nipple on the bottom of the inlet manifold. This is supposed to have some tubing with a bolt in it. Not left open or connected into the vac lines of breather piping

Thanks Stuart, I’ve already plugged that nipple under the inlet manifold. With a bolt like in the stickies info.


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[Stuart B]

Also are you sure the pipework going from the left side (drivers) inlet manifold to the firewall is not loose broken up by the firewall? That made mine cut out and really difficult to run, from mucking about with moving the pipes it's got a weird push fit connector

 

[S3AMJ]

At a guess I'd say wiring issue, plug it back in and give the wire a "wiggle" and see.

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Hi Andrew, I did move the cabling out the way, while doing all the work... it maybe that I’ve disturbed something. I’ll give that a try too. Literally soon as I plug it back in the engine cuts out


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[S3AMJ]

Also are you sure the pipework going from the left side (drivers) inlet manifold to the firewall is not loose broken up by the firewall? That made mine cut out and really difficult to run, from mucking about with moving the pipes it's got a weird push fit connector

The servo pipe from the inlet manifold Stu?


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[Stuart B]

Does the car run well with the maf unplugged because it over fuels and then unmetered air doesn't make it stall?

 

[Stuart B]

The servo pipe from the inlet manifold Stu?


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Yeah mine was leaking up by the firewall near the master cylinder, its like a swivel push fit connector, mine was cracked and loose, it made the car sound like it was knocking trying to keep running.
The TT had either already been repaired or has a different connector.

 

[S3AMJ]

Does the car run well with the maf unplugged because it over fuels and then unmetered air doesn't make it stall?

Yeah runs perfectly with the MAF unplugged, the second I plug it back in, engine cuts out. I did check all the joints with the new PCV and catch can, all are sound and tight. Underneath the inlet manifold is all sound. Only place I could think might be causing the problem is the elbow coming out of the oil filter housing.


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[S3AMJ]

Yeah mine was leaking up by the firewall near the master cylinder, its like a swivel push fit connector, mine was cracked and loose, it made the car sound like it was knocking trying to keep running.
The TT had either already been repaired or has a different connector.

I’ll check this in a couple weeks time too, I’ve not touched anything up that end, but worth a look


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[Stuart B]

That's just a breather though, my s3 came with a split y and worked fine (although made an oil smell) for about 6 months, with just some tape on. I don't think a breather leak is the same as a vacuum leak can it start with the maf plugged I and stay alive revving it? Maybe long enough to get some logs? Or fault scans?

 

[S3AMJ]

I did try revving it with the MAF plugged and it just bogged down then cut out. So can’t scan it, PITA.....


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[Stuart B]

Why not take the maf back?

 

[S3AMJ]

Why not take the maf back?

Take it back where bud? When I say it’s relatively new, it’s had about 1000 miles on it, but it’s been sat in the car 18 months haha. Car ran fine before I did the work on it. Would be coincidentally if the MAF sensor suddenly packed up..... but not ruling it out.


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[Stuart B]

Smoke test then will show any leaks.