Help! Mk1 cupra only boosting sometimes?

[Chewit]

Hi, i am new to forum and seat cupras

Bought a mk1 leon cupra a few weeks ago and have noticed that it boosts well sometimes and other times its not really boosting at all? First turbo car I've had so i dont really know too much about them.

Anyone know what this could be? Or had the similar problem?

 

[mty12345]

Welcome to the forum. Sounds like it's going into limp mode, get it scanned for fault codes.

 

[Alexis27]

N75 valve a possibility

 

[ibizacupra]

first port of call is check fault codes dude

 

[Andrewwright]

Mine droped into limp mode twice this week and no code has come up. Restart fixed the issue but still

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[mty12345]

Mine droped into limp mode twice this week and no code has come up. Restart fixed the issue but still

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Was that with VCDS though?

 

[Andrewwright]

No, am gonna get it looked at soon. I think it's the sai as it only happens when cold but will have it checked

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[Chewit]

My friend has a diagnostics computer(cheap ebay ome mind you) and it says its the secondary air pump. The EML is on but only just came on recently, but the car was not properly boosting sometimes at first. I just hadn't noticed it. Would limp mode not stop the engine from reving all the way up? As it revs right up, just doesn't boost sometimes .


What is a N75 valve?

 

[Alexis27]

N75 controls the boost and the wastegate

The secondary air pump just blows warm air onto the catalytic converter on cold startup and doesn't affect the running of the engine.

 

[Andrewwright]

N75 is what control's the boost. I've not had eml come on at any time. Did when maf was faulty but not with this issue. But mine drive's normal but drops to 5psi untill restart.

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[Andrewwright]

N75 controls the boost and the wastegate

The secondary air pump just blows warm air onto the catalytic converter on cold startup and doesn't affect the running of the engine.

Quick on the board! I take my hat off sir.

While my sai is working away on cold start i can't drive it till it kicks off at least once....If i do limp mode at best, at worst it sound like miss fire even heard a few what sounds like gulps from the engine and pop. Waiting on it to blow as i type.

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[Chewit]

Thanks guys.. will i need to change the secondary air pump in order to get the eml turned off. And will the N75 valve show up on a proper diagnostics computer?

 

[Calumcjm]

Yes N75 should throw a fault code if something's wrong with it.

I am in the same boat as you really, however I keep getting the fault code: 17705 - Pressure Drop between Turbo and Throttle Valve (check D.V.!) P1297 - 35-00 -

So far I've checked for boost leaks/vac leaks, replaced MAF, tried 3 DV's, N249 bypass, cleaned and realigned the TB but to no avail.

I've saw on this forum and others that a faulty N75 can cause this code too so I'll be trying that next. Start with the easy/cheap options first though! Could save you a fortune.

If the car is mapped it could be a bug in the software. That's what I'm blaming mine on if a new N75 doesn't sort it

 

[Andrewwright]

Are the dv you have test new and stock? Had this, put on a new one from tps and bam issue gone.

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[Calumcjm]

Tried the stock, my forge splitr which is only about 7000 miles old and my mates 2 month old fmdv008

 

[Chewit]

When i had it on my pals cheap computer it was the secondary air pump but I'll get it checked on a proper one and let yous know how i get on

 

[Andrewwright]

Tried the stock, my forge splitr which is only about 7000 miles old and my mates 2 month old fmdv008

Found this after a search...

P1297
Possible causes Faulty Manifold Absolute Pressure (MAP) Sensor Restricted MAP Sensor MAP Sensor harness is open or shorted MAP Sensor circuit poor electrical connection Faulty Engine Control Module (ECM) * What does this mean? Possible symptoms Engine Light ON (or Service Engine Soon Warning Light)

Read more:*https://www.autocodes.com/p1297.html

Hope it helps

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[ibizacupra]

familiarise yourself with ross-tech website for vag specific codes.
It can be the map in the car (even std one has this fault) and it can be maf related also



17705/P1297/004759 - Pressure Drop between Turbo and Throttle Valve (check D.V.!)

Possible Symptoms
Malfunction Indicator Light (MIL) ON
Power Loss
Possible Causes
Leaking Hoses and/or Pipes between Components
Turbocharger Recirculating Valve (N249) (Diverter Valve) faulty
Throttle Body dirty
Vacuum leak
Boost Pressure Control Valve (N75) faulty
Possible Solutions
Check Hoses and Pipes between Components
Check / Replace Turbocharger Recirculating Valve (N249) (Diverter Valve)
Check / Clean Throttle Body
Perform Throttle Body Alignment (TBA)
Check for Vacuum leak(s) including PCV system
Check / Replace Boost Pressure Control Valve (N75)
Special Notes
When found in the NAR 2.0T (BPY) check RVUTB: 01-09-03 or 2018919 for updated Crankcase Breather Valve
If the breather valve is faulty, full engine vacuum is typically found when removing the oil cap at idle.
When found in 1.8T engines, such as the (3B) B5/B5.5 Passat, check the PCV "bleeder valve". Example part number 06B-103-245
One way to troubleshoot the problem is to pinch closed the vacuum supply hose that attaches to the bleeder valve to see if the excessive crankcase vacuum is resolve resulting in a smooth idle.

 

[Chewit]

Thanks mate!

 

[BadBoy03]

Thanks IbizaCupra for more great advice! Having this issue myself and booked in for a diagnostic/smoke test, it's nice to be armed with a bit more familiarity of the fault. My car is just misbehaving now and it seems worse since it got warmer. Could be me, but it makes driving an irritation more than exciting! Thanks again, really appreciate the info!