1G 1G Naturally Aspirated / Loss of power & Vibration

[IvanovBG]

Hi guys,

Let me give you some background related to the issue I started experiencing yesterday.

I was overtaking some semi-trucks up an inclined road in 4th gear. When the RPM got to around 4500, I felt a sudden loss of power, so I slowed down right away. While getting back home, I noticed that the car loses power and starts to vibrate after around 3K RPM.

Today I did some tests, and it seems to do it in every gear, but at different RPM. In 2nd gear it starts to vibrate at around 4000, 3rd & 4th around 2500-3000. I don't know if it goes away after a certain point, as I ease on the throttle when it starts to shake, because I'm scared of doing any further damage. In neutral, I can rev it high and it feels normal. There are no weird noises coming from the engine or transmission. Shifting feels normal in every gear as well and the RPM are stable at idle.

Here's a video of me driving it:

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Any ideas on what might be causing this?

 

[CrackedDSM]

Spark plugs or ignition problem of some kind.

Also wouldn’t hurt to do a quick compression test. But I’d be more curious how the plugs look.

 

[IvanovBG]

Spark plugs or ignition problem of some kind.

Also wouldn’t hurt to do a quick compression test. But I’d be more curious how the plugs look.

I did check the spark plugs earlier today, they all looked fine to me. Keep in mind that they are on less than 2000km, so they are basically new.
I also removed the upper timing cover. What I could tell by eye is that the dowel pins are aligned and some paint marks also look aligned properly, so it doesn't seem like it skipped any teeth.
Sandly I don't have a compression tester.

Driving in the city below 3000 RPM feels normal and it accelerates the same as it did before this started happening.

Let me tell you the most recent things that have been done, in the last 2 weeks. Everything is on less than 2000km.

- Topline lifters
- Valve stem seals, which so far have resolved the oil burning issue I was having.
- Timing belt only, as it hasn't been so long since the last timing job, and all pulleys and accessory belts are good.
- I changed from 10W40 to 5w40 oil for the first time ever.

Yesterday I filled up 45 litres of fuel and added a can of Liqui Moly injector cleaner, which I've used in the past as a preventative measure.
I always drive it only with the highest quality fuel that's available here, which already is supposed to have cleaning and protection agents, so the fuel system shouldn't be gunked up.

Oil pressure with this new oil seems to be a bit lower than before, at least from I can tell on the stock gauge. This bothers me a little, but from what I've read it's in the normal range.

 

[CrackedDSM]

I’d ohm the spark plug wires and check the ignition coil. It sounds like it’s breaking up under load which makes me think ignition/spark. Someone more knowledgeable than me will comment though I’m sure.

 

[IvanovBG]

I’d ohm the spark plug wires and check the ignition coil. It sounds like it’s breaking up under load which makes me think ignition/spark. Someone more knowledgeable than me will comment though I’m sure.

The coils are like 2 years old, but I wouldn't be surprised if they've gone bad already. You never know what quality you're getting with new parts that aren't OEM.

I do still have the original ones, so I might just put them back on and see if there's gonna be a difference.

 

[97egl]

Since the issue seems to happen in lower RPM in higher gears I would also believe that you are experiencing ignition break up. I'd ohm the coils out or just swap back to the OEM. The OEM coils are VERY good units. My daily has 200K miles and still has both original coils.

 

[IvanovBG]

Since the issue seems to happen in lower RPM in higher gears I would also believe that you are experiencing ignition break up. I'd ohm the coils out or just swap back to the OEM. The OEM coils are VERY good units. My daily has 200K miles and still has both original coils.

I decided to take the coil pack off. Expected it to be a hassle, but it surprisingly took me just 20 minutes!
It's already dark out, so I'll install the OEM ones tomorrow, and report back after I go for a drive.

These are the aftermarket coils, they're from a German brand called BREMI. We'll see if they turn out to be the culprit.

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[IvanovBG]

Hi guys,

Unfortunately I couldn't get around to installing the OEM coils today, but I did use my multimeter to ohm them.

Here are the readings I got, but I'm not sure I did it completely right:

BREMI Coils:
High voltage at 20K Ohm: 16.24 & 16.09
Positive/Negative terminals at 200 Ohm: 00.9 & 00.9

OEM Diamond Coils:
High voltage at 20K Ohm: 12.82 & 12.90
Positive/Negative terminals at 200 Ohm: 00.9 & 00.9
These ones I also tested while attached to the metal bracket & connector.
At 200 Ohm, the two bottom pins read 02.2 between them, and 01.1 when each is connected with the third top pin.

Please correct me if I didn't measure something the proper way.

The BREMI coils have a higher resistance, but does this indicate they are out of spec?

 

[DSMPT]

I would double check and make 100% sure if the mechanical valve timing and balance shaft timing are good.

 

[IvanovBG]

I would double check and make 100% sure if the mechanical valve timing and balance shaft timing are good.

I'll try the coil swap as soon as possible, but after doing the ohm tests, I'm not sure they are the cause.
If they don't work, then the timing will need to be properly checked for sure.

It could have skipped a tooth, but I've driven it harder up that hill before, never had issues. The timing was for sure set properly the last time, the belt is brand new and the tensioner has like around 8K miles on it.

When I took the timing cover off after it was sitting, there was a bit of slack in the belt, but it tightened up after running the engine, isn't this normal?

 

[IvanovBG]

Okay guys, so I installed the OEM coils and took it for a drive.
It still does the same thing! I can't take it past 80km/h, without it starting to vibrate. I'll have to look into the timing when I can.

 

[IvanovBG]

Hi guys,

Just wanted to let you know that the car is running great again!

Yesterday I decided to see what would happen if I kept pressing the gas after it started vibrating, and after taking it to over 5000 RPM in 3rd & 4th gear a few times, it gradually got better and then stopped shaking completely!

It seems like something might have been clogged after all, and it just needed a bit of an Italian tune-up!

BTW, I did take it to a shop for a compression test on Friday, they told me all cylinders were slightly above 13 bars, which is more than 188 psi. For the non turbo engine I've read that it should be 192 psi, so it's pretty much right on.