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Discussion Starter · #1 ·
Hi,
I have a multiple misfire on cylinder 2.
VCDS counter goes crazy.
This is what I have done.
New plugs and coils.
Removed intake manifold cleaned all valves. Cleaned injectors, new seals on injectors and manifold OEM.
New lower pcv pipe.
Fuel trims look OK.
Any ideas what to do now?
 

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Swap over plugs\coils\injector from a working cylinder - you should have done that first! If the fault moves you know it's one of those. If it doesn't and the misfire is bad and verifiable in engine running, not some VCDS counter geeky thing, get a compression test done on all 4 cylinders.

The ECU fires 2 cylinders simultaneously (wasted spark) so unlikely to be that.
 

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Hi

A couple of ideas ,

Vacuum leak , try a smoke test
Engine condition, how many miles , also try a compression test and if you have the kit a leak down test

I've lived with a minor misfire on cylinder 3 when the engine is idling. Seems to go away once under load.

Regards

Rob

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Discussion Starter · #4 ·
Hi

A couple of ideas ,

Vacuum leak , try a smoke test
Engine condition, how many miles , also try a compression test and if you have the kit a leak down test

I've lived with a minor misfire on cylinder 3 when the engine is idling. Seems to go away once under load.

Regards

Rob

Sent from my SM-A526B using Tapatalk
Hi Rob had a compression test done.
Cyl 1 dry 170 wet 185
Cyl 2 dry 185 wet 200
Cyl 3 dry 155 wet 175
Cyl 4 dry 168 wet 185

Said ring failure and need rebuild.
 

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I have a multiple misfire on cylinder 2
Based on those compression results, cylinder 3 has the lowest readings and cylinder 2 has the highest readings which means cyl. 2 is the best! There's not a huge difference in all the wet readings and the cylinders are wet when running. Very low dry results would be more problematic for cold starting. Compression tests on modern engines should be done on a hot engine when the pistons and rings have expanded.

Engine condition, how many miles
Important question not answered!

Car engines aren't like computers or phones with precise numerical accuracy! If they repeated the tests they would get different results each time within a large margin of error. If they haven't swapped over parts between cylinders they've only done half the job. If I was looking for a ring failure, I would expect more variation in pressure results with evidence of oil burning and sooted injectors and spark plugs?

If you want to believe the shop who have eyes on and not an internet reply, go for it and hope they fix your car.
 

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Discussion Starter · #6 ·
Based on those compression results, cylinder 3 has the lowest readings and cylinder 2 has the highest readings which means cyl. 2 is the best! There's not a huge difference in all the wet readings and the cylinders are wet when running. Very low dry results would be more problematic for cold starting. Compression tests on modern engines should be done on a hot engine when the pistons and rings have expanded.

Important question not answered!

Car engines aren't like computers or phones with precise numerical accuracy! If they repeated the tests they would get different results each time within a large margin of error. If they haven't swapped over parts between cylinders they've only done half the job. If I was looking for a ring failure, I would expect more variation in pressure results with evidence of oil burning and sooted injectors and spark plugs?

If you want to believe the shop who have eyes on and not an internet reply, go for it and hope they fix your car.
I just got a gauge myself and just tested cly 1-196 2-206 3-195 4-194
More consistent readings suggesting the rings are OK. Gauge Measuring instrument Motor vehicle Auto part Circle
Gauge Measuring instrument Material property Font Auto part
Light Motor vehicle Gauge Speedometer Measuring instrument
Speedometer Gauge Motor vehicle Watch Measuring instrument
 

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As I suggested, unless you were seeing a compression reading of <100psi, there's a wide margin for error and a different result each time. Shops should repeat measurements 4 or 5 times on a hot engine and take the average. BUT you haven't said you have swapped any parts over yet or the mileage? You could do that and confirm whilst playing with your pressure gauge?
 

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Discussion Starter · #8 ·
As I suggested, unless you were seeing a compression reading of <100psi, there's a wide margin for error and a different result each time. Shops should repeat measurements 4 or 5 times on a hot engine and take the average. BUT you haven't said you have swapped any parts over yet or the mileage? You could do that and confirm whilst playing with your pressure gauge?
Yes sorry 135k
I replaced coils,plugs, pcv, purge valve and turbo diverter.
Also removed the intake cleaned the valves and injectors.
 

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Hi ,

Interesting stuff . How about a leak down test , which will show if air is leaking where it's going , ie past the rings, inlet or exhaust valves .

Some have had some luck with bg engine flush for gdi engines . The thinking is the oil ring gets clogged up and the flush can free the ring . Might need a few flushes .

Also if you pull the coil and plugs do you see and differnce in the piston surface , or any fuel . Fuel / wet might point to an injector problem . A clean piston surface might be a water leak


What did the spake plugs looks like , were they consistent in appearance?

Regards
Rob

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With this kind of fault you have to be carefully pedantic. Replacing everything in sight isn't the best way to start, although coils are a common problem. You haven't replaced a fuel injector, did you put them back in the same place and haven't swapped over No2 injector yet as I suggested?
 

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We are both telling you to use your eyes to look for different coloration on plugs and injectors. Misfire is caused by a fuel, air, or ignition problem. You can find plenty of photos on the internet showing a good clean burn.

When I've exhausted all easy possible causes my last resort is a Colortune I've had and used for years. But I can also hook a 'scope up to fuel injectors or a loop around a spark plug to look for missed ignition.
 

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I am on the same track as you. 2007 2.0T. Changed coils (red), plugs, decarbonized intake, checked and replaced PCV, changed fuel filter. I get P303 and occasionally a random misfire code. Appears when cold (slight stumble/chug) but runs fine warmed up. 141K miles. Compression is normal and consistent, does not burn more oil than it should. The last thing on my list is to send the injectors out for cleaning and balancing, but before I do does anyone else have a possible solution? Considering PCV bypass and catch-can setup as I am all out of ideas.
RGAZ
 

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Discussion Starter · #15 ·
Hi, I did a leak down test on Friday as my car is very poorly now. I am thinking that cylinder 1 & 2 are leaking air back into the intake. I am going to do it again just to confirm but air didn't hold and was blowing out of the intake manifold where I removed the PCV valve hose. My guess is after cleaning carbon is either got onto the valve seat or a burnt valve.
 

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I am on the same track as you. 2007 2.0T. Changed coils (red), plugs, decarbonized intake, checked and replaced PCV, changed fuel filter. I get P303 and occasionally a random misfire code. Appears when cold (slight stumble/chug) but runs fine warmed up. 141K miles. Compression is normal and consistent, does not burn more oil than it should. The last thing on my list is to send the injectors out for cleaning and balancing, but before I do does anyone else have a possible solution? Considering PCV bypass and catch-can setup as I am all out of ideas.
RGAZ
Hi ,

Do you have access to scanner? If so what do the fuel trims look like ?

Try a smoke test and look for leaks . I made my own for a couple of £'s see you tube for ideas .

These engines are very prone to cold start misfire . Search for diagnose Dan on youtube who has a video on this very topic.

Regards
Rob

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Discussion Starter · #17 ·
Yeah I did a smoke test and couldn't see any leaks.I have just done another leak down test I made sure I was at TDC this time and got constant readings over all cylinders. I couldn't detect any air from the intake or exhaust. So thats good. Air was coming back out of the plug hole with the hose in. Might have just not sealed properly.
 

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Hi ,

Do you have access to scanner? If so what do the fuel trims look like ?

Try a smoke test and look for leaks . I made my own for a couple of £'s see you tube for ideas .

These engines are very prone to cold start misfire . Search for diagnose Dan on youtube who has a video on this very topic.

Regards
Rob

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I only have a simple code reader. I will check out the youtube video. I don't want to hijack the thread but want to hear what you guys suggest as the next step. Are you suggesting that these is a vacuum leak? I can do a simple test to detect that if that is what you are suggesting.

RGAZ
 

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I watched the diagnosedan video on TSI cold start misfire which is what I have. It appears the stratified flap needs to shift position to allow a lean-burn cold start (vs homogeneous charge). Does the engine detect the flap position with a sensor? If the flap motion/actuator failed would the car throw a code other than the P300 series? I am thinking that maybe the actuator is not moving properly and will try and see if I can watch it during cold start. What code would activate if the actuator is not moving? What is the "default" postion of the actuator "stratified" or "homogeneous"?
RGAZ
 
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