Low RPMs bucking

[MuRCieLaGo]

Originally Posted by secondchance

You do not have to remove plenum to attach fuel pressure gauge. Front of fuel rail on the passenger side has a Schrader valve readily accessible. There is an aluminum cap similar to tire valve stem cap.

Alright thank you!

[MuRCieLaGo]

Update:

Changed fuel filter today.

Finally got a SES code, 64: Right Oxygen Sensor Circuit Lean. The SES code switches the engine back to 16 valves, right? It runs so smooth when the SES light is on, except at idle. It makes some sounds that I REALLY don't like. The noise stops when I give some gas.

https://www.youtube.com/watch?v=CsC2Z3JdEDU

I tried to get a fuel pressure gauge locally. Can't find any, I'll have to order one.

What do you guys think about this now? Please, don't stress me more than I am at the moment.

EDIT: I just started the car 5 minutes later and no more knocking sound, but god I don't like that.
EDIT #2: YES I still got the knocking sound...

[RussMcB]

That knocking noise happened to me once and it was scary but I learned here that it is a temporary lifter noise (hydraulic lifters not pumping up for some reason). It went away on its own in a short time. Hopefully yours is the same.

[MuRCieLaGo]

Originally Posted by RussMcB

That knocking noise happened to me once and it was scary but I learned here that it is a temporary lifter noise (hydraulic lifters not pumping up for some reason). It went away on its own in a short time. Hopefully yours is the same.

Glad to read this! Like I wrote, I started the car 5 minutes later and it was gone.

I hope the reliability of this legendary engine will deliver soon, because at the moment I'm not impressed.

[RussMcB]

Hopefully you'll get the bugs worked out and have years of enjoyment from it. You haven't had it long, right? When I bought mine 1/1/2015 it ran horribly but coils/injectors fixed it mostly. I also found that my stock exhaust must've had problems because I went from an under-powered ZR-1 to a healthy, strong runner with an exhaust change. I still have more to address but I thoroughly enjoy my car now, especially pushing it hard on track days. It handles the hard use with ease, so it's robust, for sure. So, have patience (I know that's easier to say than do), methodically tackle issues and it should be great again in due time.

[MuRCieLaGo]

Alright.

Still having that knocking sound problem. Oil level is OK, 5w30 High Mileage Mobil1.

Fuel pressure is OK on both pumps.

Idle: 41 psi.
FP1: 46 psi.
FP2: 48 psi.

[MuRCieLaGo]

Panic mode is now enabled.

I ran the engine and removed each spark plug wire, one by one, to see if the knocking stops. It gets worst each time I remove a wire, on every single wire. I think it eliminates the rod knocking theory?

I'm sorry, I'm used to rotary engines. I'm only beginning with piston engines. Supposed to be easier but I doubt it.

Please help me...

[secondchance]

Originally Posted by MuRCieLaGo

Panic mode is now enabled.

I ran the engine and removed each spark plug wire, one by one, to see if the knocking stops. It gets worst each time I remove a wire, on every single wire. I think it eliminates the rod knocking theory?

I'm sorry, I'm used to rotary engines. I'm only beginning with piston engines. Supposed to be easier but I doubt it.

Please help me...

Where the tensioner pulley is squeezing the drive belt, how much gap to the belt running between the water pump pulley to alternator? If the gap is too narrow, your belt may be too long allowing the tensioner to bottom out. When this happens stops on the bottom of the tensioner fixed portion and the pivot will tap each other. I chased this noise for 3-4 months.

[MuRCieLaGo]

Originally Posted by secondchance

Where the tensioner pulley is squeezing the drive belt, how much gap to the belt running between the water pump pulley to alternator? If the gap is too narrow, your belt may be too long allowing the tensioner to bottom out. When this happens stops on the bottom of the tensioner fixed portion and the pivot will tap each other. I chased this noise for 3-4 months.

Funny you mention the tensioner pulley, I took a video of it yesterday afternoon. I noticed it's loose. There's definitely a problem there, but I don't think it's related to my current issues.

It was already loose and it didn't have that scary noise...

https://www.youtube.com/watch?v=MpjCBBhHJhw

[MuRCieLaGo]

May I add that the knocking sound is irregular? Sometimes the knocking sound happens twice a second, then nothing for the next 3 seconds...