The car is a 03 pontiac grand am gt 4dr with a 3400 ,Okay so the story starts about a year ago Out of nowhere my engine starts tapping not knocking or ticking its not like a klunky inconsistent rod knock but more of a lifter tap & I can’t at all figure out what it is ,it sounds like it’s coming from the center of the engine I’ve replaced all these with brand new parts
Iac
All lifters
Oil pump
Manifold gaskets
Head gaskets
Exhaust gaskets
Oil pump relay
All popped fuses
Knock sensor
Egr
Tps
& Plenty other odds n ends
Even the rocker arm bolts have a habit of backing out which will cause a small tap but all brand new timecerts in old threads no bent pushrods & no stuck valves so with all that being said n done who out there thinks they know what this is
How many miles on this thing?
A timing chain that is stretched will start making that noise when starts coming in contact with the timing chain cover.
Tester
Ehh I think roughly 180k it’s a rebuilt so idk maybe less than that it only seems to tick after the engine is warmed up at idle if I rev it a little about 1500 rpm it goes away
I was thinking maybe timing chain but like I told mustangman it only seems to start tapping at idle after it gets a lil warm if I rev it it goes away like nothin is wrong at all but when I let off is slides right back I to tapping
I had a bad tensioner as the source of the problem. Proper diagnosis for the proper cure.
Take a valve cover off so you can watch the valve action.
Get on the crank bolt with a socket/breaker bar and rotate the engine in the normal direction while watching the valve action.
Now rotate the engine in the opposite direction while watching the valve action.
If the engine can be rotated 6 degrees or more in the opposite direction before you see any valve action, the timing chain is stretched.
Tester
Yes sir I will do that first thing in the a.m it’s 930 right now here in Indiana but soon as I do I’ll post the results to let you know ,now I’ve always been told when doin that to always turn the engine in the direction it’s supposed to go ,
so crakin in the opposite direction won’t hurt it?
No.
You’re not turning the engine in opposite direction at 800 RPM’s.
Tester
Okay I understand ,i know id be using a wrench to manually turn it ,does it matter how far I go like can I keep rotating the other way a full rotation if needed or should I not go past the 6 degrees
This is not rocket science.
Turn the engine over in the normal direction until you see valve action.
Then turn the engine over in the opposite direction until you see valve action.
That will indicate if the timing chain is stretched.
Back when engines had distributors, you’d watch the rotor in the distributor to see how far you could turn the engine before the rotor would turn when checking for a stretched timing chain.
But, your engine doesn’t have a distributor.
Tester
The symptoms do sort of sound like a timing chain problem. But if the above ideas don’t pan out
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You may have some engine-oil sludge. Remove the oil pan and thoroughly clean the inside, run full-synthetic oil through the engine for a couple hundred miles, then drain and fill again, new filter each time, do this 2 or 3 times. Finally refill/new filter with your normal oil.
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Subtle pinging can sound sort of like a tap. Double check the ignition timing, including how much it advances w/rpm. Check the spark plugs too. Too wide of gap can cause pinging. & double check there’s no air/fuel mixture related diagnostic codes. Cooling system problems can also cause pinging, so make sure the cooling system is working 100%, no air pockets, and it holds pressure. If the dash temp gauge seems to hold steady at the correct temperature in city driving but tends to wander up and down a little in freeway driving, that’s another clue the cooling system needs some work.
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There’s a tsb for the rocker arm bolt torque: 2-6-1-34
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AskPay an experienced mechanic to take a listen. Sometimes that’s the only way to figure it out. An experienced mechanic has listened to engines for thousands of hours and can tell a whole lot more than the average driveway diy’er what’s wrong just by listening. Why re-invent the wheel? If that works you can still fix the problem yourself.
It doesn’t matter which valve, pick the first one that moves, once it starts moving stop.
See how far you have to turn the engine backwards to see that same valve move.
If the valve moved down turning the engine in the correct direction, how far backwards do you have to turn the engine before the valve starts moving up.
Just to veer off into another direction, what about the possibility of a spark jumping from a plug wire? That can mimic a lifter tick or even an exhaust leak tick.
all very solid points I have new plugs & wires I forgot to mention before up top almost everything one can think of I’ve tried & or replaced with new parts like at first start it’s smooth about 3 mins into running it starts sliding into a tapping noise when I rev a lil it goes away but when rpm comes back down to idle the tapping noise slides in with it ,it seems to be tapping about half the rpm so if I’m idleing at 800 the tap is about half that not every revolution if that helps
& on another note my last forum post you replied on tester it turned out to be a crack in the bottom of the intake boot fixed it & idle is back to normal all is fine now besides the dreaded tapping