1996 3100 mpfi cold knock

[Bens71442]

Was told a valve could have hung open (causing excessive valve train lash)

Engine oil used was Valvoline 10W-30, changed every 3 to 4000 miles

Fram oil filter (used longer one) I forgot the Pt# 3,000 miles ago (last oil change I installed 1 qrt of LUCAS oil Stabilizer? Because i heard this knock last time, but it didn't last as long...another words, it knocked, I changed the oil (added the LUCAS) couldn't hear that knock at start up anymore,until yeterday. Outside temp was down to mid to low 40's with 10W-30 oil and the 3000 miles on this last oil change with the 1 qrt of LUCAS oil stabilizer.

The above was a great relief hopeing the knock was just a fluke! it has not knocked or wrapped since that last oil changed Now having reached 3000 miles, and started knocking yesterday.

I changed OIL TODAY using Valvoline 5W-30 and NO LUCAS this time. Have not cold started it since oil change today.......No knocks when hot!

How many of you guys or gals have experienced a stuck valve on 3100 or 3400 V6's ?

Having intake gasket replaced weekend after this weekend. Will have rocker arms inspected, (can't help wonder if the wear will be prevelant) since its only knocked 3 or 4 times during this failure mode???

Are 3100's common to have stuck valves? at 101K miles?

I can assume GM engineers incorporated enough piston to valve face clearance in these motors to prevent interference, in case of timing chain failure or (stuck valve) which I am believing what is happening?

AM I correct on the clearance issue with regard to the stuck open valve possibility on this 1996 3100 V6, 8th character in vin " M "code ?

No back-fires through throttle body or exhaust......but when knock was occuring, engine was rough run and LOW power. NO SES lights oil press light OFF (light has never came on in this car during knock mode!!!) Have NOT overheated in my ownership 3 years.

[torq455]

if the valve is hanging open then the piston would hit it and bend a few things--if it's stuck open at max lift.

[19Cutlass94]

Are you sure its a stuck open valve and not a lifter? These engines dont have any valve lash because they are hydrolic not solid lifters. It is very common on these engines to have noise from the lifters when cold. When the noise goes away when warm its normal. I wonder if you have a bad lifter where it takes time for the oil to get there. If it sits for a long time, the oil will drain and cause this knock.

[3.1POWER]

Might just be lifter noise on the cold engine like cutlass94 said. Does it go away if you rev the engine??? If so you may have a sticky lifter. My buddys ranger has that issue cuz it sits alot. It could possibly be piston slap too... if that were the case the sound would increase with rpm and that would explain why it goes away when the engine heats up....???

[PCGUY112887]

Piston slap. My car and my moms car (03 Buick with 3100, just hit 30k miles) sound the exact same way. Both do it when the car is cool... I mean it could be 100* outside but it will still do it till the car heats up a bit. It seems to be louder when cold outside however.

[3.1POWER]

Yea... like i said before, that could be it. The colder it is the less metal expansion of the piston there is creating excessive piston to cylinder wall clearance. The "rapidness"/volume should increase with rpm if this is the case... let me know what you find....