Rb20Det Loud Knock After Spark Plug Change

[Leeroy94]

I was driving my track car last Friday and my engine all of sudden sounded like a wrx. I took all the spark plugs out to find one had cracked severely. I went down to supercheap and bought 6 new copper plugs (bcfr6es-11) and installed them.

It was hard to start and then once started a loud knocking noise was coming from the engine. So I turned the car off, checked fault codes for engine knock but none came up (5,5 on the ecu light).

I restarted the car and then unplugged each coilpack one at a time to see if the knocking stopped but the revs only decreased and so did the knock. I revved it up to 1500rpm and the knock got faster. Then after about 10 more seconds of idling the knocking stopped and the car stalled.

I then restarted the car again and it was struggling to stay on idle and sounded like it wanted to stall, and eventually it did.

I can post videos of the knock stopping and a video of after I restarted the car.

Please help. I have no idea where to start.

[Ben C34]

Spark plugs dont crack for no reason.

What is your tune like? I will guess and say something has gone wrong and engine has died.

The plugs cracking is an indication of Way too much heat (lean) so engine has pinged to death.

Do a comp test if you like. But the knock means it's dead anyway.

[GTSBoy]

You have a real problem with the piston in that cylinder, or maybe the exhaust valve. Something broke, anyway.

[Leeroy94]

Mods are:

FMIC

Rb25 turbo

3 inch dump pump

Standard ECU

Compression test is:

Cylinder 1: 125psi

Cylinder 2: 121psi

Cylinder 3: 120psi

Cylinder 4: 125psi

Cylinder 5: 120psi

Cylinder 6: 126psi

Yeah but the car restarted after the knocking stopped. Also the car was running on 5 cylinders when putting it onto the trailer, and then immediately after the spark plug change there's a loud knock out of no where? I'm quite confused.

[Leeroy94]

No one cylinder is causing a knock because I unplugged each coilpack one at a time and there was no stop in the knock. It only reduced the speed of the knock.

[Leeroy94]

Just started it again. The knocking is definitely gone and now its missing badly on idle. To the point that it stalls unless I keep the accelerator on

[Ben C34]

Was that comp test from today?

[Leeroy94]

Yes from about 3 hours ago, before I put the new plugs in.

[Badgaz]

you might have a stuck lifter.

[Leeroy94]

I just did another compression test. Cylinder 3 is giving different results.

Test 1 cylinder 3: 120psi

Test 2 cylinder 3: 80psi

Test 3 cylinder 3: 95psi

I'm assuming either what badgaz said, a stuck lifter or, a broken valve spring.

Valve spring would explain the knocking, missing and broad variance in compression results.

[Badgaz]

chuck a video up..lets have a look

[Badgaz]

are you doing a dry or wet test?

[Leeroy94]

While knock was loud and then diminished and stalled

[Leeroy94]

When i restarted the car after the knocking stopped

[Badgaz]

i'm pretty sure thats one of your lifters making a racket.... i fixed mine with pro-ma mbl8. i would try a good engine oil flush first, fill with some cheap thin oil...then run another flush...then fill with good oil mixing the l mbl8 with the last litre of oil.

[scotty nm35]

Interesting place to put an injector...

[boostn0199]

sounds like lifter from vid but always hard to tell from a vid.

Edited April 21, 2014 by boostn0199

[scotty nm35]

I agree, it sounds like a lifter.

Why does the noise stop just before the engine dies though?

[Badgaz]

i was thinking the same thing....a bit weird.

[KiwiRS4T]

Just checking - was the spark plug on No 3 all there when you pulled it out? No bits fallen into the bore?