Car ran great then knock knock knock HELP.

[litz]

Car has been running great lately, weather getting colder. Today, took it out, first time run since Wed. last week. Got on it just a bit at a few stop signs, all well, boost was 5 to 10lbs but pulling hard due to cooler temps. Then, from a roll of about 25 mph, hit it pretty hard, not full throttle, but maybe 3/4 boost probably hit 16-17, I say probably because I was passing a car on a slight curve and did not want to look away from the road. All of a sudden heard a knock, looked at scan master, retard was 22 let off the gas, went to 19 then 17 then to 12 to 7 to 5 or 6 at idle. Car has has a knock now oil pressure is fine, temp is good.

Where do I start? Last time I had a tap, it was a collapsed lifter, this is not a tap, but a knock knock.

Car has the following:
20K on new motor. Has Champion heads, 216/216 cam, 70 series turbo and plenum, as well as front mount. 50lb injectors and SMC kit. Was getting ready to tune for the Alchy is why the boost might have hit 17, usually only go to 15. Today was going to be the day I worked it up with the alchy kit. Kit did not turn on so I do not think the boost went too high, probably not past 12 as previously today, 5 lbs was pulling real hard, and this was not nearly as hard.

Where to start? All input outside of selling it is appreciated.

Not what I had hoped for before the holidays.

 

[Nick Micale]

Bob, is this knock present at idle, and increase in frequency with RPM?

If so, disconnect one wire at a time from the coil pack and see if any change in frequency or volume.

 

[litz]

yea pretty loud at idle, not a motor guy but would suspect a rod is banging. I will try what you suggest and let you know here in a few minutes.

thanks.

 

[83ttypecooled]

boom

Hi!
I am sorry about your misfortune, but I think it could have been worse. With your mods, you could have tossed a rod. A simple knock should mean a rod bearing or two has given up the ghost. Easy to fix, but you need to pull the motor. I could be wrong about this, but given your description of events, it is unlikely. Good luck!
Dale

 

[litz]

Well,

Nick I pulled the back three plug wires off the coil pack, one at a time, so car was run with 5 cyclinders at each test. No difference in the knock. At idle the scanmaster reads 0 degrees retard, if I reve the motor a little, I can get 1.7- 2.5-3.2, nothing too serious on the RPM's maybe 1400 to 1600rpm. Knock seems to move with the rpm but the pitch does not change. pretty steady knock knock knock.

What is the old saying? they always run fastest just before they blow up?

 

[litz]

Oh, the reason for only the back 3 plug wires, knock seems to be mostly on drivers side and having limite time today to be in the garage.

 

[Nick Micale]

Check the other 3 wires when possible to see if any change in noise.

From what all you describe, best guess would be a rod/piston problem. Next step would be to pull the plugs and examine.

 

[litz]

How about drainign the oil and looking for metal? I checked the dipstick saw nothing, water or debris.

 

[Nick Micale]

Pull the filter and cut it open.

 

[litz]

Will do. Will ask my local guru to help read the tea leaves as it were.

Thanks for the input to all. Will update when I find out what happened.

 

[litz]

By the way Nick, nice photo of your car on two wheels. Don't think I will ever see that with mine but nice to dream!

 

[litz]

Update on the cause of the problem:

After pulling each plug wire with no change in the knocking sound, and pulling valve covers to find nothing, pulled spark plugs.

Plug in Cylinder #1 had its contact flattened out something crushed the tang on the plug against the electrode. All other plugs were fine.

Speaking with local Buick Guru Neal Steward, it was determined that something came through the intake to cause the problem. Pulled the up pipe from the plenum, and found that 1 of the little screws that holds the butterfly plate was missing. It is a steel torx screw that is most likely lodged in the top of my piston, which is why I still have the knock and why the spark plug was flattened.

Tomorrow night I will drain the engine of coolant and pull the head to see if I can salvage the motor with a new piston or need to yank the motor for a tear down.


Thanks for all your suggestions. Will update after I pull the head.

 

[litz]

The screw from the butterfly did not come out, but broke in half, turns out the other half of the screw, just the threads are still in the butterfly. The piston looks like it can be saved unfortuneately the head of the screw passed through the exhaust and took a few bites out of the turbo wheel. So I will be sending the turbo in for a new set of exhaust blades and the piston will be cleaned up. No real issues with the heads.

Thanks to all who offered input and especially Guru Neal Steward who directed me to the intake in the first place and has guided me this far.

 

[83ttypecooled]

That's incredible! Has the throttle body been worked on before? I never would have guessed that would be an issue. Murphy's law! Good luck with the repairs.

 

[scottyb]

Damn that sucks.

Just out of curiosity, why would it knock if the foriegn object is gone and there is no significant damage?

 

[litz]

Let me clarify me previous post. The small screw from the butterfly broke in half, some of threaded half is still in the butterfly, and the head with a small threaded shaft was lodged in the top edge of the piston. The button head of the screw then broke free from the small threaded shaft, passed through the exhaust and took a few bites out of the turbo exhaust blades.

I have never worked on the butterfly or intake since I had the car, 2 years now.

The knocking was from the remaing threaded shaft that was stuck in the piston banging the spark plug.

Good news is now with the motor out I can weld the drivers header and fix the leak there, replace the oil pan gasket and rear main seal and fix that leak, and clean up the engine compartment.

Although I would have been happier to live with the leaks and dirty engine bay and be driving the car instead of working on it.