Annoying engine problem A2 1.4 16v aua

Dimitar Timev

Dimitar Timev

Member
Hello all.

My lovely A2 1.4 16v early 2002 model AUA have a strange engine problem.
The problem happens between 1500 and 2100 rpm and its really noticeable from 3 to 5 gear.
The problem to me feels like misfire from the engine. Let say if i'm driving on 4 gear around 50km and around 2000 rpm its seem the engine is misfiring. If i accelerate above 2100 rpm there is no more problems.
If i drive on arconditing the problem seem to appear more often.

The things i already did:
Clean and adapt the throttle body.
New NJK 2397 spark plugs.
New carter breather system.
New fuel filter.
New air filter.
New hose from fuel pressure regulator to intake manifold.
And i check for vacuum leaks ,cant find any.
I have a vag com and no codes are detected in the hole car.
Check and clean the main engine earth point.
There is no oil in spark plug holes.
New the engine timing belt before 10 000km

The things i know that need to be fix:

There is strange problem with my alternator charging system. When i start the car the alternator output 14+V ,but after 10 mins the charging system outputs around 13V. I have this problem from 3 years + The alternator is whit new brushes ,new diode block and new voltage regulator.

Also i notice a strange thing with the brake pedal. If i stop on red light and stay there for 30+ seconds or more the brake pedal become firm. And if i rise the rpm the brake pedal feels normal again.


Can some one give me some advice what to check more?
How can i do i live log in vag com?
 
One possibility is that some part of your exhaust system is becoming blocked. At a guess I'd say the 2nd cat is the most likely culprit.
 
Is your problem something that developed from nowhere or something that has been getting worse for some time?

Andy
 
Misfire under acceleration / load
Most likely ignition issue
Try a set of leads / coil pack
Or if you can run the car in very dark conditions with bonnet off you may see sparkles if faulty
 
Misfire detection is one of the inbuilt features - if a certain cylinder misfires a certain number of times the injector is shut off until you reset the error or have resolved the reason. It is quite low down in the data blocks that VCDS and some ODB readers use - channels 15 and 16 cover cylinders 1-3 and 4.
 
One clue you give which has me thinking is the brake pedal feel ...................as its vacuum assist have you got an air leak somewhere...............is the hose from the engine leaking ...............at idle the vacuum is not as high as when the engine speed is higher but it should not affect the feel of the pedal unless you pump it a lot and use the reserve held in the servo unit
 
Today i measured the second catalytic converter temperature.
Car was fully worm up.
In temperature 180 C
Out temperature 220 C
is this normal ?
 
Hello,

Firstly, you have done some of the more difficult jobs already. So finding what is wrong is probably just a case of elimination.

I have experienced this problem with BBY engine.
It was when the engine was using the smallest amount of acceleration, then bump bump bump would start.
The camshaft cover breather was not working. However on an AUA engine there is no breather pipe to the cam cover so this must not be the solution to your miss fire. however I still think it maybe the crankcase breather Item 19

I would start by investigate the following low cost items. ?

Did you remove and clean the holes out in item number 2?

Make sure your happy with the condition of the rubber hose and clips of Item number 3 and Item number 2

Injector seals are also cheap and easy thing to rule off the list. Item number 8.

Cataclean additive may help?

Hope this is of some use to you ,

All the best,

Andy
 
Last edited by a moderator:
Today new catalytic converter was installed. The old one was nearly 50% clogged.
The problem still remains. strange missfire between 1500 and 2000 rpm. No faults in ecu stored.

Vag com says intake manifold pressure in idle is 480mbar.

I can upload screenshots from vag com to help.
 
Hello,

The engine ECU will use the MAP data, engine speed sensor data and air temperature to meter injected fuel.

They work as a team, if one is not working the ECU default settings for that sensor.

If the MAP was not working you would probably get an EML light or fault code.

I recently put new MAP sensors in both petrol and TDI and did not have a fault code on the TDI but did on the petrol. (Not original VAG parts used)

The engine speed sensor is easy enough to remove and clean. Behind the rubber cover Number 32.

And intake and actual air temperature can be read from VCDS.

Cheers

Andy
 
Last edited by a moderator:
Problem solved.
I remove the MAP sensor yesterday yesterday and find a big chunk of carbon stuck on the sensor.
Clean the sensor and the stuped problem is gone!
Thanks to everyone who helped.
 
Sadly my happiness was too short
The car is making the same problem again.
So i'm still searching for information.
Any help will be nice.
 
I had similar symptoms - hesitation at 16-1700rpm - with occasional engine light, and ODBII reader/VCDS reporting occasional cylinder 2 suffering misfires. Had already cleaned Throttle body and replaced the defective EGR ; new exhaust and cat were fitted at last MOT. @audifan suggested replacing the injectors, and I suspect that will be a step forward based on everything I've read about the effects of injectors being worn out (ours are on 184k) - I'm just a bit wary of pouring petrol all over the engine bay but should really man up a bit as a dud injector will eventually knacker the cat again.

Good luck Dimitar.. hope something turns up for you soon.
 
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