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Misfire cylinder 2

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Old 04-09-2017, 02:30 PM
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Default Misfire cylinder 2

Hi everyone, I am new to the forum and I badly need some help!

I bought an Audi A2 1.4 2003 Petrol for my wife.

When I bought the car the engine warning light was already present. The previous owner meant that the engine issues were no big deal and that car handled well even if the engine light comes on. When I drove the car home the engine warning light came on, and the car drove terrible, lack of power. I had to pull over and restart the engine many times to get the warning light to clear so that I was able to drive home. When warning light clears, the car ran normally.

The previous owner had the car into repair several times because of the engine warning light, but the repair shop was never able to solve the problem. They had done a lot of diagnostic and even changed the ECU and 1 coil/coilovers.

I have very little experience when it comes to repairing cars and I am on a budget. That said I got a friend which used to be a car mechanic that helps me out. He also has access to VCDS, but as he explained his skills using VCDS is not that good.

VCDS reports that there is a misfire cylinder 2 (P0302 - 35-00 - Misfire Detected). I can drive the car fine, but very often when car come to a stop still, the engine warning light comes on and the car then runs terrible. This also happens when I start the engine and let it idle for 1 3 minutes without hitting the accelerator. If I start driving right away, there is no problem as long as it does not idle for above a minute or so. What we have done so far:

- Changed ECU (Second hand ECU)
- Replaced injector on cylinder 2
- Swapped coil/coilovers between cylinder 4th and nr 2, also from 3th and nr 2.
- Replaced knock sensor
- Replaced spark plugs
- Replaced fuel filter
- Regular service, oil, oil filter, air filter.
- Compression tests on all cylinders:
o Cylinder 1 = 16.2 Bar
o Cylinder 2 = 17.1 Bar
o Cylinder 3 = 16.8 Bar
o Cylinder 4 = 17.8 Bar
- Fuel pressure and fuel pump delivery rate:
o Fuel pressure while engine idle: 47 psi
o Fuel delivery 1600 cm3 in 30 sec (battery 12.80 V, ignition off, remotely/manually run)
- Inspected the engine loom wiring harness. Measured resistance between the different connectors such as to coils and injectors. This was just a quick and dirty check to see if we can verify if there was some resistance difference it the readout between the different connectors/pinouts for the units, no difference was noticed.
- Tried to spray starter gas around the intake manifold looking for leaks, but no rise in idling.
- Throttle housing calibration done using VCDS, OK
- Checked and verified timing belt alignment, OK
- Cleaned MAF sensor, OK
- Coolant sensor, OK
- EGR valve calibration done using VCDS, OK

We noticed that there was a color difference while changing the sparkplugs. Sparkplug on cylinder nr 2 was much darker than the others. We used a flashlight inspecting each piston through the sparkplug hole, and we noticed that the piston on cylinder 2 was a little wet compared to the others.

When we disconnect the fuel injector on injector 2 while the car is running, there is just a slight difference in how the car is idling. When we disconnect any other injectors there is a very clear difference in idling. When my friend used VCDS and advance measuring blocks selecting Lamda readout, misfire cylinder 1-4, he thought that the lambda sonde/O2 readout was variating too little, close to 0 all the time. He decided to disconnect the O2 sensor. When disconnected O2 there was no misfire registering in VCDS and the engine was idling much better, no engine warning light. My friend had a new aftermarket O2 sensor lying around which is for an Audi A3 1.6. The wiring color code is the same as the original car O2 sensor/connector, so we decided to replace the O2 sensor with the one for the Audi A3. The readout in VCDS for the O2 sensor now showed a much more variable readout than before, but the misfire count on cylinder nr 2 started again, and as soon as it reached around 85-100 misfires the engine warning lamp came on again and then also the O2/Lamda readout stopped and went to 0. When we clear the TDC (misfire cylinder 2) for the engine while engine is running, the O2/Lamda readout start displaying values again, but so does the misfire counts for cylinder 2, and then engine warning comes on and O2 readouts stops again.

So we concluded that if O2/Lamda is disconnected there is no misfire readout in VCDS, the engine runs smoother and no engine warning light.
My friend is suspecting that cylinder nr 2 may have leakage problem in the intake manifold, or there is some kind of vacuum leakage (have not been able to trigger the problem using starting gas), maybe EGR issue (do not know is there is EGR tube for all 4 cylinders, or just one common tube/vent)

I sincerely hope that someone here is able to point us in the right direction, maybe there is something that we are missing or overlooked.

LOG from VCDS:

Address 01: Engine Labels: 036-906-034-APE.lbl
Control Module Part Number: 036 906 034 CA
Component and/or Version: MARELLI 4MV 5949
Additional Info: WAUZZZ8Z73N006323 AUZ7Z0B2128047
1 Fault Found:

16686 - Cylinder 2
P0302 - 35-00 - Misfire Detected

Readiness: 1010 0101


And here is the vehicle identification:





And this is the old spark plugs, the one who is more gray is from cylinder 2:

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Old 12-08-2017, 08:16 PM
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If 2 is misfiring, it will be a different colour, and wet.

What fuel grade are you running? I'm just repairing a Golf 1.4 TSi which I pick up cheap because the previous owner had been running it on 91 octane. Destroyed No.1 piston. Your compression figures look ok, so it would seem unlikely that you have that problem, but I'd suggest trying higher grade fuel and see what happens. Run the car almost dry (around 10km to empty) before filling up on premium fuel, and see what happens.

The best way to look for an inlet leak is to pump smoke under pressure into the air inlet just after the filter box (engine not running): if there is a leak, you'll find it.
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Old 12-09-2017, 02:01 PM
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Originally Posted by Languid View Post
If 2 is misfiring, it will be a different colour, and wet.

What fuel grade are you running? I'm just repairing a Golf 1.4 TSi which I pick up cheap because the previous owner had been running it on 91 octane. Destroyed No.1 piston. Your compression figures look ok, so it would seem unlikely that you have that problem, but I'd suggest trying higher grade fuel and see what happens. Run the car almost dry (around 10km to empty) before filling up on premium fuel, and see what happens.

The best way to look for an inlet leak is to pump smoke under pressure into the air inlet just after the filter box (engine not running): if there is a leak, you'll find it.
Thanks for the reply!
The misfire is now fixed. It was a leaking valve seal.
But there are still some problems:
2 Faults Found:

17961 - Barometric / Manifold Pressure Signals
P1553 - 35 - 10 - Implausible Correlation - Intermittent
17912 - Intake Air System
P1504 - 35-00 - Leak Detected

Readiness: 1010 0101

And I have already ordered Smoke-Tek EVAP Smoke Machine Diagnostic Emissions Vacuum Leak on ebay.
Did that before I read your post. We have tried with spraying start gas around every possible hose in the car, but with no look, therefor this smoke machine.

I have almost used the same amount in parts as I payed for the car. My worst purchase ever.
I have a new maf sensor and I have ordered another one, just in case the one I got was faulty.
I don't know if the throttle house could give us that fault message?
The car runs fine at startup, it goes a little high on idle but after it has wormed up the idle becomes jumpy and it goes to limp mode with all the christmas lighting on in the dash.
So this car has been a challenge.
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Old 04-20-2018, 02:48 AM
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Hi!
l have the same problem with my A2 from 2001. As soon as l m standing still at a red light cylinder 2 shuts of and the car runs really bad. Sounds like a steam boat...
Where in the engine, did you change the broken "VALVE SEAL". Cost? Difficult? Please get bak to me, l ve had it in the shop a couple of times and nobody has been able to find the problem..
//Jockewass...
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Old 04-20-2018, 03:37 PM
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Originally Posted by jockewass View Post
Hi!
l have the same problem with my A2 from 2001. As soon as l m standing still at a red light cylinder 2 shuts of and the car runs really bad. Sounds like a steam boat...
Where in the engine, did you change the broken "VALVE SEAL". Cost? Difficult? Please get bak to me, l ve had it in the shop a couple of times and nobody has been able to find the problem..
//Jockewass...
That's sound like mine car. I bought a valve holder tool that works with a air compressor. You take off the top cover, and then I used the valve holder tool witch I screws in to one of the spark-plug holes, and that blows air to keep the valves from dropping down.
And I used a spesial tool to compress the valve springs. That can be a hard job because there are a ring that is cut in half that is difficult to get back in place after you have changed the valve seals. The cost to do it your self is not high. The highest costs is the tools. The parts is not that expensive.
I guess I used about 2.5 hours, and the main problem was getting the to half rings in place. Search for valve seals replacement on youtube and you will find many videos.
The error went away after that. But there was a new error code that came up, and that was due to the throttle body, and after changing that. The last error was gone, but only to give me the misfire cylinder 2 again after I drove the care for some miles.
After checking the compression on cylinder 2, it was lower then the other three, and that could either be because one of the valves is not moving like it should, or the top or the cylinder could be damage.
I have a mechanic who will check the valves, top and cylinder for me tomorrow. So I will try to keep you updated on what it is.

Sorry for my English.

Regards

Glenn
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