My 00 XJR has this low speed under load knock/clatter. almost like a detonation noise, but I think not. when taking off slowly under load. thoughts. not overheating. chains and tensioners replaced. Fuel system cleaned. Plugs new.
Im baffled

Some type of belt tensioner noise?
super charger?(Dont know what a bad coupler sounds like)
converter? Def does not sound like mech internal engine noise.

give me what you got.

thx.

 

have you replaced the fuel filter?

otherwise, best guess is that your secondary fuel pump is toast.

 

New filter was installed when I replace both pumps in December. Runs like a spotted a$$ ape otherwise.

 

bump

 

I think I would put a stethescope on the blower snout and listen for similiar but quieter noise at idle.

 

i'm thinking SC noise. May be hearing a failed coupler in the SC. under just right load spring loaded coupler may be chattering.Took belt off and feel some play in coupler by turning back and forth by hand.

Will listen to bearings tomorrow.

 

Strangest thing. I noticed a bad SC idler pulley bearing and changed it before I left shop last night. Knocking noise still there low rpm under load. Was getting low on fuel, stopped at Exxon and put in fuel. so far no knock noise...hmmm...I have been using various sources and having this knock with diff suppliers. could be a fluke. I still plan on rebuilding SC Snout.