P.Lindblom

Lupo 1,4 throttle problem

27 posts in this topic

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

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

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

This. And also fitting the standard airbox back on.

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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!

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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.

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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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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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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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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?

img0239o.jpg

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

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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:

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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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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?

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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.

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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

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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.

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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

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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.

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This is what the car does...

Youtube Video ->

Original Video

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?

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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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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?

Any chance of a picture of this vacuum pipe, I've been looking for it, but can't seem to work out which one you mean.

Edited by NOCK

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I have similar problems, at the moment im leaning towards the TB seal, so ive ordered a new one and reply once it's fitted.

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Today I had VAG check the car and they couldn't say what is causing the problems. They did a whole bunch of tests and discovered that the engine is misfiring intermittently on cylinder 3. They told me it's probably caused by either:

1. A bad injector

2. Intermittent loss of compression in cylinder 3 (is that even possible?)

I really really hope it's just the injector. I'm so tired of this car right now, but if I could at least get it running properly I would probably be able to stand all the other small issues. A new injector is £180 so I'm going for a second hand one for £40, but first I'm going to ask the mechanic how they figured out which cylinder is misfiring. Then I'll swap the no. 3 injector with one of the others and see if the problem follows.

By the way, is cylinder 3 the third from the left or from the right if you're standing in front of the car looking at the engine?

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Hi P. been reading this thread with interest as just before i bought my car a 1.4 s my ex had similar issues to those you describe. In short various bits were changed following suggestions from all she asked, in the end i bought the car and i have a spare throttle body as i fitted a brand new unit to the car just beofre i bought it, but the most significant improvement to the idle and general running cam from changing the temp sensor.

Now i am not syaing this was any stroke of genius, more like a what else can it be type of thinking, but it did make a difference. and at £6 or so a cheap way of ruling out anything minor that may make a difference.

Having said all that, i have a throttle body if you want to talk further on it, mail me direct.

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Hi P. been reading this thread with interest as just before i bought my car a 1.4 s my ex had similar issues to those you describe. In short various bits were changed following suggestions from all she asked, in the end i bought the car and i have a spare throttle body as i fitted a brand new unit to the car just beofre i bought it, but the most significant improvement to the idle and general running cam from changing the temp sensor.

Now i am not syaing this was any stroke of genius, more like a what else can it be type of thinking, but it did make a difference. and at £6 or so a cheap way of ruling out anything minor that may make a difference.

Having said all that, i have a throttle body if you want to talk further on it, mail me direct.

Hello mate,

That's interesting. I just ordered a new temp sensor. I don't think I'm going to need another tb, though, as I've tried three different ones with the same result but thank you anyway :)

I just had a look at the protocol from the VAG garage and apart from the misfiring there are two values that are slightly off. The engine load at idle is 30%. According to the mechanic it should be below 20%.

Also, the intake pressure is 500mBar when it should be 240-420mbar.

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