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Lupo 1,4 throttle problem


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#1 P.Lindblom

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Posted 09 December 2010 - 11:46 PM

Good evening,

I recently bought a 2000 Lupo 1,4 16V which seems to be working perfectly except for one small issue.

When turning the ignition key the car starts up right away without any problems and although the idle seems to be steady I'm noticing a slight sputtering. The main problem is that if I press the gas pedal just a little bit the revs drop for about half a second before they go up. This means that I have to give it more throttle than I'm used to with other cars when pulling off, in order to prevent the car from stalling.

Apart from that the car runs great. It currently has an open K&N filter sitting on top of the throttle body. I thought the filter might be clogged up by the goo from the oil breather hose but the car is acting the exact same way even with the filter removed.

Any suggestions would really be appreciated. I'll be in Manchester this weekend but when I get home to Sweden I will continue searching for a solution. Also, the car is not showing any fault codes.

Please help me :)

Edited by P.Lindblom, 03 February 2011 - 07:33 AM.


#2 NOCK

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Posted 10 December 2010 - 09:14 AM

Try cleaning your throttle body. I had a similar issue a few years back.

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#3 Lal B3N

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Posted 10 December 2010 - 09:19 AM

Try cleaning your throttle body. I had a similar issue a few years back.


This. And also fitting the standard airbox back on.
Previous Arosa sport 119bhp - 115 ft lbs.

#4 DarkStryder360

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Posted 10 December 2010 - 02:01 PM

Try cleaning your throttle body. I had a similar issue a few years back.


10000% this. I had this issue for 2 years before finding out it was just down to cleaning out the darn Throttle Body!! Done it last in June, think I will do it again soon!

#5 P.Lindblom

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Posted 15 December 2010 - 12:14 AM

Thank you for your suggestions. Today I removed the throttle body and the first thing I noticed was that there was no seal between the TB and the manifold.

I cleaned the TB properly with carb cleaner before I made a seal and refitted it. I then had my girlfriend keep the revs at a steady 2000 rpm while I sprayed some more carb cleaner into the intake.

The first time I started the car after I cleaned the TB the EPC light came on and it's been lit since. The idle is still the same, a little bit dodgy and sputtering. When I had the air filter off I looked at the throttle valve while idling and it was never completely still, it was opening slightly and closing rapidly, making a sort of rattling noise.

Could the nervous throttle valve along with the lit EPC light indicate that there's something wrong with the DBW sensor somehow? Can you re-calibrate it yourself perhaps?

I just ordered an airbox. I'll let you know if it makes any difference, but I must say I doubt it. Tomorrow I'll order a Vag-Com unit as well.

#6 JoeA

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Posted 15 December 2010 - 11:45 AM

If you disconnect your battery for a while, then reconnect, it should reset all the sensors? If the light stays on there's an actual problem, someone on here should have some idea.

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#7 NOCK

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Posted 15 December 2010 - 12:59 PM

If you disconnect your battery for a while, then reconnect, it should reset all the sensors? If the light stays on there's an actual problem, someone on here should have some idea.


That, or a 2 minute session on VAG-COM.

About 30 mins should be enough to clear all of the fault codes. If they don't come back up then all is good. If they do then you know that further investigation is needed.

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#8 JoeA

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Posted 16 December 2010 - 04:41 PM

That, or a 2 minute session on VAG-COM.

About 30 mins should be enough to clear all of the fault codes. If they don't come back up then all is good. If they do then you know that further investigation is needed.

That's the bobby :)

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#9 P.Lindblom

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Posted 17 December 2010 - 12:57 PM

Right, I've realized the EPC light doesn't come on right away after I start the engine and start driving, that's because when the engine is cold the idle is perfectly fine at a steady 1100 rpm. After a short trip the temperature is where it should be but then the idle becomes really dodgy. I believe the term is hunting. It sounds like the engine is about stall but just in time it stabilizes itself. This is when the EPC light comes on.

Also, yesterday I stopped at a red light and when it turned green I didn’t give the car enough throttle so the engine stalled. I quickly started it again without problem but then the check engine light started flashing. I was in the middle of Stockholm so I had no chance of pulling over. The car drove nicely though and after a minute or so the check engine light stopped flashing and kept lit. Since then the EPC light has behaved the same way as before but the check engine light has stayed lit. 30 minutes without battery power didn’t help.

Today I found a post that caught my attention as it almost perfectly describes my symptoms.

The hunting and clicking is caused by a stuck vapor canister purge valve. The valve is on a vacume line. When it gets stuck open too much air enters the engine at idle or low rpm. This will cause the engine to hunt and stall as soon as any load is put on it if you do not rev it hard. The engine will over-run when coming to a stop and probably stall. It can come and go putting the chack light on. The quick fix is to just un-plug the solenoid. facing the enginebay it is located on the left hand side just infront of the suspention mount it is half balck half blue on every lupo i have seen. unpluging it will mean the car is driveable again but the check light does come on. It is 100% safe as long as nothing else happens that goes undetected because the light is already on. The part is about £70/80 from VW, they may or may not know what you are talking about but i would not bother going to VW. The part is easy to find at a scrapyards if there are Lupos / Polos. A number of other VAG cars share the part as well. Any other problems come along to clublupo.co.uk

I tried unplugging the valve but when I started the engine the idle went straight to 1200 rpm and the throttle didn’t work at all. I connected the valve again and the hunting continued.

I’ve noticed a sort of air sucking noise coming from the area around the throttle body. My current idea is that the TB is sucking in air that the ECU isn’t accounting for. I looked for split vacuum hoses behind the TB but I couldn’t see properly. I will take the car inside and check it later. However, I found something that looks like it should be connected to something else.

Here’s a picture. I’m thinking it might be a temperature sensor for the airbox. Could it have anything to do with my engine hunting?

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This is how the engine behaves when it almost stalls. For some reason the idle was really really bad when I recorded this. Anyway...
http://www.youtube.com/watch?v=PTaq41LOFHA

Edited by P.Lindblom, 17 December 2010 - 10:08 PM.


#10 P.Lindblom

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Posted 20 December 2010 - 03:23 PM

I just had the car diagnosed and the following fault codes showed up:

17912 Intake air system : Leak detected - p1504 - intermittent.
17961 Barometic/Manifold pressure signals : Implausible Correlation - P1553 - intermittent.


The mechanic thought it might be the vapor canister purge valve so I'll check that one again. He also though it could be a faulty throttle body.

I've read about a lot of different suggestions like the throttle position sensor, temp sensor and the idle control valve but I don't know where to find any of them :wacko:

#11 NOCK

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Posted 21 December 2010 - 12:32 PM

I just had the car diagnosed and the following fault codes showed up:

17912 Intake air system : Leak detected - p1504 - intermittent.
17961 Barometic/Manifold pressure signals : Implausible Correlation - P1553 - intermittent.


The mechanic thought it might be the vapor canister purge valve so I'll check that one again. He also though it could be a faulty throttle body.

I've read about a lot of different suggestions like the throttle position sensor, temp sensor and the idle control valve but I don't know where to find any of them :wacko:


I would have thought that :
17961 Barometic/Manifold pressure signals : Implausible Correlation - P1553 - intermittent.

Would mean that you need a new MAP sensor?

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#12 P.Lindblom

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Posted 27 December 2010 - 01:39 PM

I would have thought that :
17961 Barometic/Manifold pressure signals : Implausible Correlation - P1553 - intermittent.

Would mean that you need a new MAP sensor?

Where is the MAP sensor located?

I'm also looking for the idle control valve, where can I find it?

#13 midi

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Posted 31 December 2010 - 11:17 AM

i have this same problem on my lupo.
i took it to a VW repair centre, an they came out with no fault codes. so i took it back to the garage were i bought the car from (as its still under warranty) and it gave a fault code on there diagnostics that it was the MAF sensor. they cleaned the throttle body out, and this helped a bit, but currently awaiting a new sensor. they mentioned it could be a split breather pipe. might be worth checking that.

#14 NOCK

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Posted 07 January 2011 - 01:45 PM

Where is the MAP sensor located?

I'm also looking for the idle control valve, where can I find it?


I've read that the MAP sensor is found on/in the 'intake manifold'. However I haven't had a look yet. I think I need to replace my MAP sensor too, so if anyone knows where it is found can they please post it up.

Idle control valve is built into your Throttle Body I believe. And a new Throttle Body isn't cheap :(

it was the MAF sensor


I've read a thousand times that only the 1.4TDi lupo has an MAF sensor :blink:

Edited by NOCK, 07 January 2011 - 01:47 PM.

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#15 P.Lindblom

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Posted 24 January 2011 - 08:28 AM

Okay, another update. I managed to get my 10 ebay Vag-com cable working and I did a Throttle body alignment. After that the idle became steady and I've had no fault codes since.

However, the initial problem still persists. When the engine is idling and I push the throttle just a little bit the RPMs go down before they start going up again. I'll try to get a short video of it later today. This is very annoying since I have to push the throttle quite a lot whenever I'm pulling off from standstill or the engine will stall.

I'm thinking it might still be a vacuum leak but the fault code saying there is a leak is no longer there.

#16 P.Lindblom

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Posted 02 February 2011 - 04:47 PM

This is what the car does...



#17 NOCK

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Posted 02 February 2011 - 04:49 PM

I did a Throttle body alignment.


Did you give the throttle body a thorough clean first, and then bolt it down REALLY tight?

Edited by NOCK, 02 February 2011 - 04:49 PM.

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#18 P.Lindblom

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Posted 02 February 2011 - 05:09 PM

Did you give the throttle body a thorough clean first, and then bolt it down REALLY tight?

I gave it a thorough clean a month ago. That's when I discovered there was no gasket between the throttle body and the manifold so I made a new one. I will remove and clean it again on friday.

#19 P.Lindblom

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Posted 27 March 2011 - 09:45 PM

This is what the car does...

http://www.youtube.com/watch?v=u4pcLa0sGww

I've now replaced all the HT leads, the coil pack, the spark plugs and the air filter but there's still no difference at all. I spoke to a mechanic who suggested a new throttle body and I think I'm going to get a new one soon, but I don't think it will fix the problem.

An intake vacuum leak still sounds plausible. Is there a way of checking this using the Vag-Com?

#20 Owen33

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Posted 22 April 2011 - 11:59 AM

do you still have problems with this?
My car has done this really badly since the engine was refitted, had a good look at it yesterday, and when we took of the vacuum pipe from the fuel rail it ran perfectly?
We found a spare tube and fitted it, its not perfect but its 100x more better! down to the plastic part of the tube sitting loose in the rubber attachment ends.
Can't be sure if it will be your issue but won't hurt to try it?
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