Help with misfire on opel astra.

Hello. Im having a problem with a recently purchased car. I have tested many things and perceived a lot of different odd things so this can be a bit long but i will do my best to keep it short.

Car:

2008 Chevrolet Vectra = Opel Astra in EU
60K Miles on dash. Purchased with 55k
X20SE Engine 2.0L 4 cyl 8 valves completely stock.

If you need more details about the car I can provide them.

Problem:

I uploaded a video to youtube showing the noise the engine is making i filmed it on drivers seat with cellphone to the ground so you can hear better the exhaust noise.:



I have a rusty exhaust pipe after the catalytic converter and im not fixing it on purpose so i can hear clearly the engine noise. Ok the video is starting at idle and then keeping 2K rpms. Im pretty sure that the noise are missfires.

Thats the problem now this what I already diagnosed and I know about:

1- Pulled sparplug 2, is covered in carbon deposits and black dry residue. Other plugs are fine. A bit yellowish. All of them are identical NGK, very few miles on them, and to car spec.
2- Exhaust stinks of fuel on cold starts. Goes away after a few minutes of running. No leaks on fuel sistem, i checked that the smell comes from the exhaust only.
3- No codes present or stored. I have a basic OBD2 scanner and nothing is showing up.
4- On cold starts also i have 7 to 9 negative SFT. Sometimes even reaching -12%. Also goes away when car is warm. Rest of the trip both trims stay between -1 and 1.
5- Sometimes if for some external reason the car stalls. Its harder and takes a lot of cranking to start immediately. If you just wait kind of 20 to 30 seconds. Car will start without problem.
6- Power balance test didnt show anything out of the ordinary. But im blaming cylinder 2 due to the fouled sparkplug.
7-Did a cylinder leak test. All cylinders were between 5 and 8% of leakage.

SO...

After all this I think the obvious choice was a leaking injector. I dropped a bottle of cleaner in half a tank. Pulled injectors and changed basket and orings. Tested them connected to the battery very briefly. Also pulled fuel rail with injectors attached and made the pump run for a bit. No leakage.from any injector. Still I switched injectors 2 and 3, put new sparkplugs on 2 and 3 and run the car for a week. Then i pulled both new sparkplugs. To my surprise it was again number 2 the fouled sparkplug.

Then i focused on spark. Tested coil and wires. Everything seems normal. I tested the wires with a test probe and spark was the same on all cylinders. Also wires are new.

Now im at a loss of explanation or ideas of what to do, except rip the head and rebuild it. Which i dont want to do in a fairly low mileage engine like mine that also shows minimal leakage.

Any thought will be appreciated. Because i dont intend to start throwing piles of cash and partes on the car just in the hope of something that will fix it. Thanks

Bonus:

Generic pic of the car:

Try to spray same water on top of the coil pack, maybe a spark leakage!?

Pull the spark plugs out and see if one cylinder is different. Those coil packs fail internally quite often.

I'm with Paul, this sounds like an ignition misfire. Does the car exhibit misfiring or low power while driving? Are you concerned about the noise only, or is there a perceptible engine performance issue that goes along with it?

Double post. Please delete.

Paul6004 wrote: Pull the spark plugs out and see if one cylinder is different. Those coil packs fail internally quite often.

Hey thanks for you reply. I already mentioned that i did that.

"1- Pulled sparplug 2, is covered in carbon deposits and black dry residue. Other plugs are fine. A bit yellowish. All of them are identical NGK, very few miles on them, and to car spec."

Im going to test the water on the wires today when i get home.

Tyler wrote: I'm with Paul, this sounds like an ignition misfire. Does the car exhibit misfiring or low power while driving? Are you concerned about the noise only, or is there a perceptible engine performance issue that goes along with it?

I missed your post so here goes an edit:

IF there is a performance degradation while driving , I wasnt able to feel it. But when aircon turned on, sometimes I feel like the car wants to stall when getting off the line. However that also might be to the sluggish DBW accelerator.

Im concerned about the noise. Im the kind of person that want a car to run in the better shape possible. Im also going to add some minor mods (headers, intake and catback) and I want to start on a problem free/clean slate car.

Ok guys. I havent updated this because i work in my driveway and the weather has been pretty bad these days but today I was able to do more work:

Today i changed the hydraulic lifters on the engine because they were ticking just a bit after 30 to 60 seconds on cold startup. So I was able to perform again a cylinder leak test, just because i wanted to make sure nothing changed, and nothing did. Still good compresion on all cylinders.

Pics of leakeage test:
What else I did?

I pulled coil, wires and plugs out of the car. Findings below:

What I did last time i was under the bonnet is switch wire 2 and 3 (remember plug 2 was the black one). Still plug 2 was again black and others were fine.

Plugs pic (in order 1 to 4)
drive.google.com/file/d/1Jj8rM2eBjM4G_d-...hEV/view?usp=sharing

Plug 2 in more detail, look its odd that its just getting darker on one side isnt?
drive.google.com/file/d/1yecnKprmmRhRp_8...QpC/view?usp=sharing

Coil pack underneath was covered on a 2mm thick oil and dirt layer. Also was pretty dirty on the upside. I didnt find any cracks but I did find rust on the bottom of the cover of the coil pack. Checked resistance 0.7 ohm on primary and 11-12 ohm on the secondary coils. Both coils were identical values. Workshop manual doesn't say what is the correct value.

Pic of rust on coil:
drive.google.com/file/d/1XKazMR7ZD_DjWNm...js6/view?usp=sharing

I cleaned the wires which I changed when bought the car because previous wires showed spots of sparks jumping. Those that i put 5k miles ago were "double silicone 8mm sport wires" but look the same as the OEM, just a bit thicker, and seem pretty solid. So, cleaned the wires and looked for white spots or damage and couldnt find none.

Cleaned everything. Sanded the rust of the bottom of the coil cover then assembled everything in car again. Nothing changed.

So I asked someone to accelerate engine to 2K RPM then i started soaking wires and coil in water with a spray, i could hear the engine missing like usual but I couldn't see any spark. BUT "I THINK" (I would say 50% chance) that sometimes I heard too loud the sound of the spark like it was jumping, but the noise came directy from the plug if it was jumping at all.

Conclusions: Maybe is time to sentence the coilpack? The rust in the cover was the only odd thing I saw in the whole engine. But I ordered an oscilloscope from the states. It will take a week or two to arrive. I will wait until I can share some graphs before starting throwing parts at it.

In the meantime any more toughts would be appreciated.

Hi Martin!

From what I read you have a coil with plugwires? Have you tried to pull out spark with a testlight? Compare the nr 2 with a know good. You should be able to pull spark out at least an inch or so from the tip of the boot.
Another problem might be intake manifold gasket. Eventhough fuel trims are negative, it could pay to check it out. Spray some water over it with a squirt bottle. I’ve experienced this myself to be effective.
Hope this will help you along.

Dennis

martin511989 wrote: Conclusions: Maybe is time to sentence the coilpack? The rust in the cover was the only odd thing I saw in the whole engine. But I ordered an oscilloscope from the states. It will take a week or two to arrive. I will wait until I can share some graphs before starting throwing parts at it.

In the meantime any more toughts would be appreciated.

Yes, sentence the coilpack to eternity in the rubbish bin! (I post as Paul6004 when I'm on the work computer).
I have changed a few of those coil packs on Astras, they are actually quite cheap.
Generally they are difficult to work with because it's all one piece but there is a test you can do - I sometimes remove the coil pack and place
it upside down and fit 4 spark plugs with their ground 'lobes' bent over backwards so the spark needs to jump a bigger gap, to give it a bit of
a load. Then I take a long piece of wire from ground, with the insulation bared back at intervals to coincide with the spark plugs, wrapped around each plug, so the spark has a ground, and crank the engine and watch that is is sparking on all of them. This is not an absolute test because it still doesn't get as much load as an engine under compression but may show that the spark isn't getting out of one of the coils.
Also check the insulators on the coil stalks, one of them may be split.

Ok guys. Bad news.

Today i was driving to work and the car felt very rough and very low on power after a few blocks. I checked the dash and check engine light went on. I have a bluetooth ELM327. So I pulled to the side of the road and read the code with torque app. P304 so Misfire on cyl 4. I performed a quick power balance check pulling injector connector but I didnt feel like any cylinder make a difference. I hesitated a bit but drove it to work. When the car warmed up it went a little bit better. So near my job I purchased the OEM coil pack, came home and replaced it. No change.

So new coil pack and no change. I sprayed all around the intake manifold with an air leak detector spray (some liquimoly product). No change on revs. Also car doesnt have a MAF. It has a MAP in the plenum.

So I pulled all the wires again and with the tip of the test light I tested for spark. Spark was able to jump 1 inch in all wires. No much more but I think thats fine?

As a last minute test I unplugged one by one each spark wire and put the engine at 2000 RPM. The pops that you can hear in the video above? I cant hear them if I pull plug wire 2. If I unplug the other wires is still very noticeable.

Also that pop, now I can hear it even when idling so condition is worsening. Maybe the P304 was the correct diagnosis but incorrect cylinder?

This is my daily driver and I really need it and its driving me mad. I cannot even go to the dealership as they are pretty useless. I have seen his shop. I have better tools and even a better scanner that what they have. When I asked them some time ago to pull some codes when i didnt have the correct scanner for this car. They pulled it with some really cheap chinese scanner so I ask them about the Tech32 scanner (official GM)... they said it was broken. Dealers are a complete joke in my country so I am reallly on my own.


EDIT: When I tested the spark jump it was one inch. But wasnt always blue. Sometimes the spark looked red-ish.

I thought it was the long coilpack that's all one piece over the spark plugs. Obviously not if it has leads. Can you post a picture of the engine and coil pack please?

I cant take one now, but this is from the internet. Mine is the same but a lot dirtier with oil and dirt, also I have a factory exhaust heat shield that protects the sparkplug boots.

.

Also here is the pic of the new coil I installed.

So im posting again cause I just changed on the street a new set of plug wires. No change. Thats all the part throwing i would do. Because as I expected, throwing parts was not the solution. Oscilloscope is arriving end of next week I hope. Still hearing new ideas.

Have you replaced spark plugs yet? You could try swapping the spark plugs to different cylinders to see if the fault moves.

Thank you Desmond for taking your time to assist me here.

Yes, the first thing I did was change the plugs. I switched injector, wire and plug, at the same time between cylinders 2 and 3. And then ran it for a week. Pulled plugs and the fault didnt move from cylinder 2.

So i did plugs, wires and coils with no avail. Im leaning now to discard the ignition as the culprit. But isnt an injector either, as I said moved injector 2 to cyl 3 and the fault didnt move.

Is a compression test needed even if I alredy did the leakage test and performed ok? Are actually pretty expensive those tools here. I have a leak test but I purchased it in the US and took about 3 weeks to arrive.

Hi Martin! Yes a compressiontest would tell you a lot. Couple of things to check as well, considering you have misfires/rich condition
- engine timing. If the engine does not breathe right. It can cause rich symptoms. A warmer car needs less fuel so it could explain the better fuel trims at warmer temps. But dont quote me on that one. Dont have a lot of experience with this.
Also, have you checked your fuel pressure regulator? Maybe thats causing some issues as well.
Hope you’ll soon tackle this problem.

Dennis