Problem with 5cylinder 1

[Mike1002]

It concerns an Audi 2.3l 20v 5 cylinder. With pin coils and Bosch injectors. I have connected everything to the ECU and checked the wiring harness. All setting correct in the computer. Now the engine starts, only it runs on 4 cylinders. Cylinder 5 does not participate but the sparkplug does get wet. I made a list of what I checked.

What checked/checked/replaced

Wiring harness measured
New sparkplugs mounted
Compression measured
Fuel pressure measured 3/4bar
Mapping checked
Injector flow test done
Crankshaft signal test done
Checked firing order
Sparks from sparkplugs tested
Checked inlet valves to see if they open
Inlet gasket reassembled and additional liquid gasket used in between
Temperature sensor connected
Oil pressure sensor connected
Engine timing checked
Ignition time controlled with timing light

All sparkplugs spark when upside down. But when the sparkplug is mounted in the head, the spark is not strong enough or there is no spark at all.

 

[TugboatEng]

Some engines come with these types of plugs from the factory now. The Japanese manufacturers seem to be favoring A standard or platinum/iridium center electrode with a pair of copper side ground straps for their more higher performance engines.

 

[Mike1002]

Thanks for your responses, I think 3DDave may be right about using too much fuel. the plugs are new and when they turn black start with brake cleaner. there MUST be a spark. we can rule this out! we cannot rule out whether it sparks at the right time and whether the injector is working correctly. my lambda sensor indicates that the fuel correction needs to be reduced by -80 percent. too much fuel is measured in the exhaust.

 

[jean genibrel]

That spark plug does not look new. It has been run for several hundred miles from the looks of the carbon inside the ceramic. Ditto on the type of spark plug to use. A single electrode is plenty.

 

[Mike1002]

So what to do now? This is how the sparkplugs look from the running cilinders

What do you think about it? It is a new sparkplug

 

[jean genibrel]

Have you checked the battery and alternator outputs? It is not unusual to have a misfire from low voltage.

 

[CWB1]

My ol' smoky riding mower fouled plugs with carbon just like that every 4-6 hours. It would run great for a month then refuse to start, so I'd pull the plug and use a dental pick to clean it out, wire brush, reinstall, and run it another 4-6. It had a vertical crank/horizontal cylinder, snd was about as cheaply built as possible so I didn't bother trying to repair or even be upset when the connecting rod broke ~600 hours.

JMO but I suspect you have an oil control issue, maybe stem seals, rings, or bottom end damage.

 

[BrianPetersen]

Black like that could be bad oil control or way rich. It could be that the whole engine is on the verge of rich misfire, but the one cylinder due to inherent variations is too rich to fire under some conditions. Why it's way rich, and what to do about it, is the next challenge.

 

[gruntguru]

Probably way-rich.

Does it blow black smoke or blue? Black = rich, blue = oil. (and don't say neither - I won't believe you)

je suis charlie

 

[Mike1002]

So I did a leak down test to check the rings. Looks good

There comes black smoke from
Exhaust

 

[LittleInch]

How is the airflow measured?

There's nothing about that in your original list of things checked.

I suspect the engine mgt system thinks there is more air flow than actually is present, hence more fuel than your engine can burn.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[BrianPetersen]

... and which fuel injection system/controller/ECU does it use? Does it have OBDII? Is the fuel injection system/controller/ECU meant for this engine, or has it been remapped to suit this engine?

You need to find out why the fuel injection controls are commanding so much fuel to be injected, because I'm now more convinced than ever that the biggest part of the issue is that it is running obnoxiously rich.

 

[moon161]

LI, I was thinking something similar. Bad MAF or connection, or bad ECU.

 

[enginesrus]

So for some reason it is running way to fat. Have you checked fuel pressure? Did you check manifold vacuum? How about the engine coolant temp sensor for the ecu not the one for the gauge, is it correct resistance for the correct temperature? And same for the map, mass airflow sensor? Open up the ecu and check for leaking capacitors too, or any other water damage, when everything else checks okay then ecu huge suspect.
O2 sensors? Need a good scan tool. And like mentioned above simple things like new spark plugs, coil etc.

 

[3DDave]

It's a new ECU - apparently the OP replaced all the sparky bits on an engine that was good enough and now it's not. It should be closing the loop on the O2 sensor in the exhaust and trimming from what it expects, not continuing to force feed.

Nothing quite as much fun as a Franken-car with a problem.