Revving & boosting irratic...video's included. Please help

[cupra-barn]

Hi all,

Right I've bee having this issue for 10 days or so now and is progressively getting worse so need some advice.

1 - Car revs irraticly on idle.

2 - Car over revs when changing gear by about 200/300 rpm.

3 - Car is dropping boost.

Ive tried the common fault fixes, Ive checked all wiring, checked all hoses, both cleaned and replaced throttle body, replaced map sensor, checked inlet mani bolts, checked and cleaned clutch position switch, checked the fuses, checked the plugs, checked all coilpacks are seated, and reset on vagcom.

Ive got no fault codes coming up related to any of this.

Nothing has been done to the car recently so cant be any new mods causing it.

This is how it idles.


And this is how it drops boost.


Im really at a blank and beginning to lose hope and heart in the car.

Does anyone have any suggestions???

 

[cupra-barn]

Anybody at all?

There must be someone thats had a similar problem or has some ideas.

 

[grahams81]

Alright Barn, what codes have you got..... Your saying none that could be connected but maybe they might shine a light for someone.

The idle looks totally wierd allmost like your running a set of race cams, if your at a dead end i would check the cambelt timing mate, it'll only take 10mins to check for a man of your calibre.

Also stupid question but the aircon wasn't turned on when you videod it idling ?

 

[virdi]

MAF.? Dump valve.?

 

[yellonvi-R]

What dumpvalve is it?

 

[csd_19]

Can you log both throttle position readings when its idling? Compare the pedal to the TB reading.

 

[traumapat]

Second the maf, unplug it and see if idle returns?

 

[Mark One]

I'm struggling to think of a single problem that would cause both problems.

You say you've replaced the MAP sensor, what about the MAF? Could try that by getting a new one or perhaps even borrowing one of another car for a bit?

Looking at the videos again, it's an air control problem. So you need to be looking at MAF, MAP and vac hoses. Perhaps an air leak after the MAF (most of the system) that would cause the MAF to MAP air flow calculations to be unequal.

 

[cupra-barn]

After spending all day working on the car we had a result.

A fuse had blown! Couldn't believe it.

I've still got my revving issue but that could be a lambda so gonna try replacing it.

Cheers for all the advise and comments guys.

 

[Mark One]

What fuse was that?
Lambda sensor can cause a hunt at idle. You can normally diagnose them by unplugging the sensor and seeing if it improves.

 

[cupra-barn]

I can't remember what it's called.

It's got a picture of the engine management and is the 4th fuse up from the bottom in the middle row inside the car