Engine Knock [Archive] - GrandAmGT.com Forum


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10-06-2009, 10:43 PM
The top end of my engine was freshly rebuilt (by me) and after a while I got it running finally. At first it ran TERRIBLY but after it ran 30 minutes, it slowly got smoother but it was still running a little rough. Only problem besides running rough which I suspect is normal anyways, is a knock sound. At first it had it every second or 2 at idle, then after it ran smoother and smoother the knock decreased. It is also dependent on RPM's somewhat, as the higher the engine revs, the faster it knocks. It sounds like it might be somewhere in the valvetrain. Tried using a screwdriver as a stethescope but that didn't help too much...

Any suggestions on what this is?? My mechanically inclined friend said it might be the rocker arm slapping the valve stem. However this does not make sense because it does not slap at all times or even close to every stroke.

10-14-2009, 07:30 PM
Take a broom handle, no broom end :D and run it along the valve covers. Listen for varience in sound. Be careful around the turning parts. This should allow you to get back from the engine enough to actually hear something. Where is the sound from in your opinion? Top end, lower end? Lifters could not be pumping up but usually doesnt happen when new unless you got a bad one. turn the front wheels and listen for change, maybe even take the belt off for a quick run and see if it stop then, then you know its not inside the engine, or maybe it is. Let us know what you hear..............

10-14-2009, 07:39 PM
A mechanic checked it out and he said from listening to it, the timing is just off and the knock sound are big misfires.

10-14-2009, 10:27 PM
You're posting multiple threads relating to the same problem.

It'd be nice to have all the sypmtoms in one thread.

10-14-2009, 11:52 PM
well i made this thread before I found out about the timing, etc... THIS IS THE THREAD NOW.

10-15-2009, 10:19 AM
Could you have mixed up the push rods? There are two different lengths in these motors.

10-15-2009, 12:46 PM
Could you have mixed up the push rods? There are two different lengths in these motors.


Ill bet you put the pushrods in the wrong places. You could have also overtorqued the rocker arms. My friend redid his LIM and just cranked down on the rockers and it would barely run at all.

So, did you put the pushrods back in the correct places (exhaust and intake) and did you use a torque wrench on the rest of the parts?

10-16-2009, 12:01 AM
Yep, it's all torqued right and the rods are in the right spots

10-16-2009, 10:47 AM
does it throw any codes? like a cylinder X misfire?.....

check that you have the plug wires in the right spot... my dad fixed some flooding(h2o) on an older grand am. then it ran bad, i took one look at it and told him two plug wires were swithched, and it fixed a slew of problems right quick...

and not to nock on your skills, but a pushrod is a possibility, its a simple mistake to make, i made it once...

get back with us, and we will help you get it right...G/L

10-16-2009, 10:45 PM
I said the push rods are in in the correct places. So are the plug wires. I have a question:
There are 2 parts (if that's the correct way to phrase it) to the crank position sensor, the 24X and the 7X. Are they both in the same connector?

10-17-2009, 11:07 AM
No, the 24x sensor is on the outside of the engine behind the crank pulley and reads a reluctor ring in the back side of the crank pulley. The 7x sensor reads a toothed ring on the crank shaft itself and the sensor goes inside the block itself on the side by the firewall.

As we've already told you though, they should have NOTHING to do with the problem you are having. If there was a problem with either of those sensors you'd have a code in the pcm and it would be reverting to a default ignition timing which is actually retarded. You would not be seeing 30 degrees of advance, and that is normal.

10-17-2009, 03:36 PM
Okay, so Aaron what could be causing my problem?

10-17-2009, 06:32 PM
Any number of things. If your engine wasn't running rough before the repairs.. it could be air in the fuel rail, injectors that need a proffessional cleaning, bad spark plugs... Hopefully you didn't put Bosch plugs in there...

The ticking noise would usually be chalked to normal lifter noise.. but the fact that you have misfires to go along with it tells me something else happened during that repair.

Get your scan tool and see which cylinders are misfiring then diagnose from there. Run a compression test on that bank. No cylinder should be less than 80% of the two adjacent to it. Normal compression at sea level is usually between 170 - 185.

If that points out nothing, switch plugs with an adjacent cylinder to see if the miss moves. Try a test wire after that if the miss stays in the same place.

10-17-2009, 06:46 PM
Engine was running really bad before the repair but I assumed that was because of the head gasket leak. Spark plugs were good before the repair. Injectors I'm not sure about. How would air get in the fuel rail? And the scan tool only reported one error. I don't remember the code but it was the general misfire one.

10-18-2009, 10:35 AM
P0300 is engine misfire detected. If you have a scan tool though you should be able to scan while the engine is running for current and history misfires on individual cylinders and that might help narrow down your problem.

10-18-2009, 09:02 PM
The only codes stored were P0300 and P0301 and that was the cylinder with the leak.