What is causing this knock? video inside
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From: Chicago
What is causing this knock? video inside http://www.badassperformance.com/misc-vid/knock.wmv
(2.8megs)
First:
I realize there are a lot of threads about knocking problems and I have searched and read them all (I think). Everyone describes the sounds differently and Im not sure if the problems are the same as mine. Because of this, I uploaded a video of the engine with the sound. Hopefully, someone who has solved this problem before will have an extra minute for me!
History:
The car is a 1987 Rx7 with a 2000 Camaro SS w/T56 engine transplant. It has been running poorly for about a year until I found out I plumbed the fuel incorrectly and was getting too much fuel. I installed a corvette fuel filter/regulator and the car ran great for three days. Then after filling up the fuel tank and getting hard on the throttle, the knock showed up.
Problem:
Engine knock sounds like a higher pitched Diesel sound. It is RPM dependant and louder at certain spots. I cant tell if it is every, or every other RPM that it knocks.
Things I have done, or know about:
Oil pressure is 40psi when cold, goes down to 30 when hot and gets to 60 with higher RPM. I have EFIlive scan tool at my disposal. I have not noticed anything out of the ordinary. No knocking detected, LT fuel trims around -5 to -8%. I think my fuel pressure is a few psi low at 54. I am new to the software and willing to run more logs if it could help. I ran the balance test and all cylinders seem the same, but each time I run it, some cylinders are left out. They are different each time. I dont know if this is normal. Im still trying to fix the VSS sensor. Spark plugs and wires are new. I also put in a bottle of NOS octane booster when someone suggested bad gas (I got the gas at a newer and popular BP station). People suggested the engine was hitting something. I dont think the engine shakes at a high enough frequency to make that noise. There are some close fits, but I havent found anything hitting. With a homemade stethoscope, I think the noise is most evident when I touch and front of the oil pan or the water pump. The knock is still there with the main belt removed. The car feels fine power-wise, but Im afraid to really drive it much. I dont want to do more damage.
My only theories:
Get the fuel pressure up to 58psi with a booster pump.
Bad main or cam bearing?
Bad timing chain?
The engine has 40-50k miles on it. It ran great for three days. What could cause this?
Please help, thanks!
Tom
(2.8megs)
First:
I realize there are a lot of threads about knocking problems and I have searched and read them all (I think). Everyone describes the sounds differently and Im not sure if the problems are the same as mine. Because of this, I uploaded a video of the engine with the sound. Hopefully, someone who has solved this problem before will have an extra minute for me!
History:
The car is a 1987 Rx7 with a 2000 Camaro SS w/T56 engine transplant. It has been running poorly for about a year until I found out I plumbed the fuel incorrectly and was getting too much fuel. I installed a corvette fuel filter/regulator and the car ran great for three days. Then after filling up the fuel tank and getting hard on the throttle, the knock showed up.
Problem:
Engine knock sounds like a higher pitched Diesel sound. It is RPM dependant and louder at certain spots. I cant tell if it is every, or every other RPM that it knocks.
Things I have done, or know about:
Oil pressure is 40psi when cold, goes down to 30 when hot and gets to 60 with higher RPM. I have EFIlive scan tool at my disposal. I have not noticed anything out of the ordinary. No knocking detected, LT fuel trims around -5 to -8%. I think my fuel pressure is a few psi low at 54. I am new to the software and willing to run more logs if it could help. I ran the balance test and all cylinders seem the same, but each time I run it, some cylinders are left out. They are different each time. I dont know if this is normal. Im still trying to fix the VSS sensor. Spark plugs and wires are new. I also put in a bottle of NOS octane booster when someone suggested bad gas (I got the gas at a newer and popular BP station). People suggested the engine was hitting something. I dont think the engine shakes at a high enough frequency to make that noise. There are some close fits, but I havent found anything hitting. With a homemade stethoscope, I think the noise is most evident when I touch and front of the oil pan or the water pump. The knock is still there with the main belt removed. The car feels fine power-wise, but Im afraid to really drive it much. I dont want to do more damage.
My only theories:
Get the fuel pressure up to 58psi with a booster pump.
Bad main or cam bearing?
Bad timing chain?
The engine has 40-50k miles on it. It ran great for three days. What could cause this?
Please help, thanks!
Tom
Thread Starter
Teching In
Joined: Jun 2006
Posts: 19
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From: Chicago
Is there some test I can do to know for sure what is wrong? If it might be a rod bearing, how do I know for sure before I start rebuilding the bottom end? Should a 40k motor have a bad bearing?
Get an engine stethoscope and with the engine running listen to the oil pan, block, valve covers, timing chain cover, and wherever else on the engine and see where it is the loudest.
Good luck
John
Good luck
John
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Thread Starter
Teching In
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From: Chicago
I just changed the oil and found a pea sized wad of metal dust on the magnetic drain plug.
With a stethoscope, the sound is loudest on the oil pan towards the front. I can also hear it somewhat on the water pump (belt removed). Nothing on the heads, valve cover or exhaust.
With a stethoscope, the sound is loudest on the oil pan towards the front. I can also hear it somewhat on the water pump (belt removed). Nothing on the heads, valve cover or exhaust.
Sounds like a rod bearing.
You can try and isolate it as to which cylinder it is by disconnecting 1 plug wire at time while the engine is knocking.
When you get to the one causing the problem the sound will change and or be almost gone.
I hope I'm wrong.
Good Luck
Ryan
You can try and isolate it as to which cylinder it is by disconnecting 1 plug wire at time while the engine is knocking.
When you get to the one causing the problem the sound will change and or be almost gone.
I hope I'm wrong.
Good Luck
Ryan
I would say main bearing.I had a spun rod bearing on my m6 a couple of years ago and it didnt sound like that more of a ticking sound.that thing is a loud knocking.good luck.
Thread Starter
Teching In
Joined: Jun 2006
Posts: 19
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From: Chicago
Well, it seems everyone thinks it is a rod knock. I will start pulling the bottom apart this weekend (I should have been racing by now). My new question is this: Why did the car run great for a few days? It was in a yard for a few months. I got it running and was driving it in and out of the garage for a few months. Then I got everything sorted out and it was great for about three days. Then the knock started. I guess I'm wondering what caused it and how can I prevent it once I fix my engine? Oil pressure was good. Fuel was at 54psi, but the PCM seemed to compensate for it. The car was running very rich (64 psi) for a while when I was trouble shooting it.
