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[8364]

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Beware of wall of text.

This is about a 2000 Omega 2.2, Y22XE as far as I know. Earlier this year the car failed the yearly inspection due to emissions, high CO if I recall correctly. They also said they thought it was running a bit rough/irregular, which I had not experienced myself at that time.

I was advised to replace the spark plugs, which I did. Made no difference at all. Then after a little research (on here I think) I replaced the front O2 sensor. Then I went to the inspection again the value ended up right at the maximum allowed limit, which was good enough to pass but I still felt that it should be better than that.

Some time after that I started seeing the orange light with a car and spanner. I had a mechanic connect his diagnostic tool and he said that my EGR-valve is bad and I should clean it. But that valve is nearly new, replaced 2 years ago, so I did not alter it at that time.


So here's what I then discovered:
When starting from cold, the rpms stays on like 1100 for a while and then start decreasing (kind of how it used to be). But instead of just decrease, smooth out and stabilise, the idle just gets increasingly more erratic/rough until it abruptly goes up slightly, stabilises and the light goes on. In that state, I can drive normally but something feels wrong, like it is sluggish, jerky, low on power or something.

I have also noticed it hesitates to start some times. Like it takes a few more turns to get it running, and when it does start the light goes on immediately an stays until I shut it off.

If I restart the engine while up to temp, it usually does not come on and everything feels pretty normal. But if I shut it off, wait 5-10 minutes, I can get it to do one of the above again.

But if I start the engine from cold and I start driving immediately the light very rarely goes on (if ever).

Had a second and third opinion from larger auto repair shops, they also insisted that something is wrong with the EGR. I then replaced it with a brand new one, but the problem is still there. Also everything is exactly the same if I leave the EGR unplugged...


List of the things I have done since the failed inspection mentioned above:

• Replaced spark plugs
• Replaced coil pack
• Cleaned throttle body, hoses and the black metal pipe
• Replaced front oxygen sensor/lambda
• Replaced cam position sensor
• Replaced the EGR valve
• Tried to clean the airflow sensor (there wasn't much to clean)
• Inspected the pipe to the pressure regulator (could not see anything wrong)
• Replaced air filter
• also the valve cover gasket was replaced by a mechanic earlier this year

All replacement parts were brand new.

I cleaned the plug wells before fitting new plugs and the new coil pack.

The code that the mechanics were seeing is P1405 which points to EGR, but I'm doubting this as nothing changes when it is disconnected.

One of the mechanics also saw these codes below, but I'm not sure if it is relevant or if that is because I have been messing with these parts (lambda, cam sensor, maf etc):
P0170, P0136, P0130, P0340

Any ideas? Any more tests I can do myself?

ChatGPT thinks it could be a failing throttle body or MAF. Are any of that likely?

What about the crank position sensor?

[Doctor Gollum]

What make of sensors did you use?

Any sign of a head gasket failure?

[Osmo]

I had same kind problems with one engine some years ago. It was mass airflow meter sensor.
It looks clean, but doesn't work properly. I changed it and everything was ok.