What are signs of a failing turbo?

So update on my testing today. Checked compression with the oscilloscope and found a minute dip in revolutions. So it took it for a road test while he read the parameters on his Snap On scan tool. Nothing abnormal, fuel trims were good.

Bought some plugs and came back to the garage. Performed a clear flood mode and checked compression on cal #4, I got 149psi. Performed a leak down and they were within 3-4 psi of each other.

With the car being so hot and being outside in the 95 degree weather I only changed #4 plug. It looked like the original plug and the car idled and drove a lot better. I think I will change the harness, coils and plugs and drive it again. I was able to use a denso but should I switch it to a NGK? I had some slight cylinder roughness in #4. I will post up

Feedback Knock -4.00/0.00

Fine Knock Learn -5.02/0.64

Roughness Cyl #4 0/2

DAM 0.875/0.875

So far the car drives with no misses or hesitation. I drove it for over 2 hours and no issues. Could this all have been the result of a bad spark plug/lack of tune up? I was planning of doing a full maintenance and only had the timing belt/water pump done and tune up was next.

So update on my testing today. Checked compression with the oscilloscope and found a minute dip in revolutions. So it took it for a road test while he read the parameters on his Snap On scan tool. Nothing abnormal, fuel trims were good.

 

Bought some plugs and came back to the garage. Performed a clear flood mode and checked compression on cal #4, I got 149psi. Performed a leak down and they were within 3-4 psi of each other.

 

With the car being so hot and being outside in the 95 degree weather I only changed #4 plug. It looked like the original plug and the car idled and drove a lot better. I think I will change the harness, coils and plugs and drive it again. I was able to use a denso but should I switch it to a NGK? I had some slight cylinder roughness in #4. I will post up

 

Feedback Knock -4.00/0.00

Fine Knock Learn -5.02/0.64

Roughness Cyl #4 0/2

DAM 0.875/0.875

 

So far the car drives with no misses or hesitation. I drove it for over 2 hours and no issues. Could this all have been the result of a bad spark plug/lack of tune up? I was planning of doing a full maintenance and only had the timing belt/water pump done and tune up was next.

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Go with NGK in all 4. Just a backup step here... Did you replace the intake air filter? I had forgotten to do mine last year and oh boy the car drives much smoother with a new panel installed. Simple WIX filter may help?

Ok, will get a set of NGK's, the Denso was the only one available at the parts store I was at the time. Yes intake and cabin filters were the first 2 things I did when I bought it, so its about 5 months old. Thanks for that video too, it made the job easier though the engine was hot