Top end knocking sound + erratic AFR/Fuel trim


New member
Hey guys I recently bought a fully built engine that was built by TJRC in CO about a year ago and sat ever since, never installed or ran.
Since the car has been running I've noticed when it's at full temp it has a strange knocking sound at idle and even while driving. I'm partially suspecting the cam follower or the vacuum pump because it sounds like that noise is coming from that area.
I also noticed the AFR and fuel trim seems to be kinda bouncing around which also made me suspect the cam follower or vacuum pump affecting the HPFP. I had another HPFP so I swapped that out and I didn't notice any difference so I don't think I'd have 2 bad HPFP's, though the one I had was also used. I took some videos and combined them into 1 video. I uploaded it to youtube, here is the link:

I also took datalogs via Accessport and can upload those as well. I also have VAGCOM.

I’ve done some research and can’t really find anything the same as what I’m experiencing without any codes or anything.

Let me know if there’s something I’m missing, I’m not exactly sure what’s going on.
I have a new cam follower coming in today and will be swapping that out.


New member
So I replaced the cam follower with a brand new OEM one and I noticed the new one was a lot tighter of a fit going into the vacuum pump, almost as if there was a lip worn into the vacuum pump. And the noise and driveability is a lot worse with the new one. So I’m thinking it’s the vacuum pump for sure.
Here’s a video with the new one in.


New member
I swapped out the vacuum pump and still have no change.
AFR is bouncing from 12-16
STFT bounces from like 0.9-1.10+
LTFT stays around 1


New member
Well, I’m at a loss again.
Did an oil pressure check, as I was getting the car hot it seemed to get a little louder.
Oil pressure ending up being perfectly within spec.
The AFR and FT started being even more erratic. I ended up getting some CEL codes - P0087 fuel rail/system pressure too low
P2293 - fuel pressure regulator 2 performance
So I decided to swap out the HPFP again to just be sure this one wasn’t bad.
Sure enough the shaft was sheared.
So I put the other one in and at first everything was fine it sounded good the numbers were stable and perfect. Test drove it and it started getting louder and becoming erratic. So I parked it I’ll pull the HPFP out tomorrow to make sure it didn’t get sheared also. But now I’m thinking something might be wrong with the cam or timing…
Not sure what else would cause this.


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