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Charged A/C yesterday and after about 10 miles of driving the car started acting funny…upshifting then downshifting between 3rd and 4th, eventually started losing power (with or without A/C on), barely made it through my driveway to park it and overall just started running like crap. Then it started making this odd knocking sound that is loudest around the front of the engine/around the exhaust manifold. It doesn’t do it at idle, only when you press the throttle and as soon as you release it goes away. I poked around with a screwdriver to my ear and didn’t hear anything out of place. Oil is clean even after about 2K on current oil change, and is at the correct level. All other fluids are clean. Trans fluid is clean, smells fresh. Everything in the ignition and fuel system is new. I only use top tier gas. So far I have told it could be: cracked/leaking exhaust manifold, rod knock, spun bearing or some other internal catastrophe. I have spark on all 4 plugs. Had the valve cover off recently, everything inside was tight and spotless. Also replaced oil pan gasket recently, everything in the bottom end was also tight and looked very good for its age. Not sure what to do or who is on point with their guess. Also I don’t believe the A/C had anything to do with it, that was just the last thing I did before this mess. When you turn the steering wheel, or if the cooling fan comes on or I turn the A/C on while it is idling, it tries to die.
Here are some videos to show you what I’m talking about:
https://www.youtube.com/watch?v=awe2hTr1-Ac
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Here is also a clip of my exhaust which normally does not sound like a helicopter.
This is a shot in the dark, but maybe there is a broken valve spring or a tossed rocker arm. I know you recently had the valve cover off, but I would take it off again for a look. The noise seems to be a top end noise rather than a bottom end noise as best as I could tell from the video.
Speaking of that…I actually recorded a video a while back before all of this happened as I was digging around under the valve cover. Maybe you could check it out and see if the “play” I had was acceptable, or possibly bad…which could have been foreshadowing this whole event in the first place.
Um… yeah! Too much play. You need to pull your cover again. At the very least, you need to adjust the valves. The only rockers with play should be the ones where the valves are fully closed. With the engine at TDC on #1, only 4 valves should have only slight play, the others tight. When the cam is rotated 180 degrees, the other 4 should have slight play and the first 4 should now be tight.
Service Procedure
With engine at normal operating temperature, remove rocker arm cover.
Disconnect high tension lead from ignition coil.
Position No. 1 piston at TDC compression stroke.
With engine in this firing position, adjust the following valves:
No. 1 and 2 intake valves and No. 1 and 3 exhaust valves.
To adjust valves, loosen locknut, then turn adjusting screw until specified feeler gauge can be positioned between valve stem and screw. While holding adjusting screw in position, tighten locknut.Rotate engine to place No. 4 piston at TDC compression stroke.
With engine in this firing position, adjust No. 3 and 4 intake valves and No. 2 and 4 exhaust valves as outlined above.After adjustment is completed, install rocker arm cover and connect ignition coil high tension lead.
Clearance Specification
Intake 0.010 in Note: Hot
Exhaust 0.012 in Note: HotI edited my post to include the valve adjustment procedure in the event you don’t have it. You need a box wrench, 12mm IIRC, a flat blade screwdriver, and a set of feeler gauges. It isn’t hard to do. You can use the starter to bump the engine to the correct positions, or you can use a socket wrench on the crank pulley. Make sure the key is off to prevent an accidental start.
I’ll look into this once I get home from work. If they are out of adjustment, what would bringing them back into spec do for my original problem (if any) ?
Once you get the valve cover off, you’ll know if any parts have come loose or broken. Other than that, the valve adjustment could actually be the problem. The valve clearance is important for the engine to breathe properly. If it doesn’t, it won’t run properly. A loose valvetrain makes a lot of noise.
Well let’s hope I’m actually that lucky for once, haha. Someone on another forum swears it’s a spun bearing. It would be a shame if it was something worse than a simple adjustment considering how much money the previous owner put into this car and the fact that I got it for next to nothing.
If it’s any consolation, that is a very clean engine compartment. This car has received a good dose of care.
I took some pictures before I checked the valves. They were actually in spec.
[quote=”Evil-i” post=140277]If it’s any consolation, that is a very clean engine compartment. This car has received a good dose of care.[/quote]
The car came with a fairly large stack of receipts and work orders for pretty much every nut, bolt, and oil change the car received.
I don’t doubt your word, though, they sure looked way loose in the video. The noise seems to appear like its coming from the higher part of the engine than the lower part, though. Granted, it’s hard to tell sound direction on the video. Another thought, perhaps the timing chain tensioner has broken. Can you pull off the timing cover and check the slack in the belt?
Yup, I actually did that as well…have to take it off to take the rocker cover off. The belt was nice and tight. It was replaced within the past few years…it was a Gatorback belt and not OEM.
At this point you may need to get a very long screwdriver or mechanic stethoscope to pinpoint exactly where the noise is the loudest. The bad news is we’ve just examined the ‘easy’ things… 🙁
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