Rally68

Pulling in to the driveway last night I noticed a knock coming from the engine bay. I parked the car immediately, but was able to determine that it's only noticeable at idle--you can't hear it when the engine revs. The sound is valve train speed, just like a ticking lifter would be but definitely a knock.

2 interesting things: First, I just lowered the idle speed by about 200rpm. It idles right around 500rpm in gear and about 650 in park.

Second, I noticed my oil pressure was higher than it usually is at idle. It normally reads below 35psi at idle and right between 35psi and the second tick mark (50-ish psi?) at speed. Last night when I shut it down, the needle was straight up and down at 35psi at right around 600rpm warm idle--not ridiculously high, but higher than I've ever seen it at idle...

I'm going to grab a stethoscope and try to narrow this down but is it possible that the low idle is allowing a lifter to get hung up in the bore? Could this cause higher-than-usual oil pressure?

Thanks in advance for any insight...

CaseyJones

A knock at idle like that could be the water pump bearing or the fuel pump rod. Most valve train noise is more of a click or tick. I would also be concerned that the timing chain is getting a little loose. Isolate the general area of the noise and let us know.

REELAV8R

The higher oil pressure combined with the knocking would seem to indicate that there is some kind of blockage to oil flow.
When was the last time the oil and filter were changed? Are you using a different oil than you usually do? ie higher viscosity?

hugie82

I have a fuel pump on a k5 blazer knocking. Just before I was ready to pull the engine I listen with a 3 foot extension and zeroed in on the pump. The pin holding the arm was lose and the heavy pushrod was banging against the cam. Good luck. Check everything! Including torque converter bolts.

gcusmano74

Yes. That makes a loud-enough-to-scare-you noise. Had that with a 77 Olds 88 with a Chevy 350 in it. (Remember when GM did that?) A new fuel pump and we were good to go.

scrappy76

Yes, definately check the fuel pump rod and the torque converter bolts.

Rally68

Thanks for the replies guys. Turns out I won't get to look at the car until Friday, though I may have a chance to change the oil tonight. May or may not have time to cut the filter...

Been about 400 miles since I changed the oil & filter, no change in what I use, Royal Purple 10W40 and K&N filter--same for years.

I will check the items mentioned but the oil pressure acting strangely has me concerned that it's something in the block (besides a fuel pump pushrod).

I'll be back!