engine knocking on startup cold
#21
09-10-2012, 02:43 PM
I notice something new about my knock this weekend while at a big Ferrari get together in Eureka Springs Arkansas. I was more than a little embarrassed as I started my car and slowly drove it through the parking lot to the hotels front canopy were I parked and turned the car off while I went inside to discuss my bill with the manager. After returning in about 10 minutes and restarting the car in the presents of a nice Corvette owner, to my surprise, and relief, the noise was gone.
I think the short one minute drive and then 10 minute wait time must have heated up whatever parts are knocking. So my conclusion is heat, and not a lot of it, is required to quiet things down. This also remove oil pressure as a culprit.
The lower octane relief is interesting as it does sound like a diesel engine, but lowering the octane? The knock is also cam speed. It’s at the same tempo as the injectors which means it only makes its noise only during combustion. I have asked the jag dealer to kill one spark plug at a time when we try to find it next time I take it in, I’m not sure if they really want to see it again anyway. Is there any way of doing this through the ECU?
How about wrist pin or small end rod knock. I know the piston does reshape itself as it warms up. That's why a piston has Cam Grind ( being oval) of 1 or 2 thousands.
Also here in the USA we only have 85,87 and 91 (sometime 92 or 93) I'm not sure how they measure it in France but it may be similar octane to ours.
I think the short one minute drive and then 10 minute wait time must have heated up whatever parts are knocking. So my conclusion is heat, and not a lot of it, is required to quiet things down. This also remove oil pressure as a culprit.
The lower octane relief is interesting as it does sound like a diesel engine, but lowering the octane? The knock is also cam speed. It’s at the same tempo as the injectors which means it only makes its noise only during combustion. I have asked the jag dealer to kill one spark plug at a time when we try to find it next time I take it in, I’m not sure if they really want to see it again anyway. Is there any way of doing this through the ECU?
How about wrist pin or small end rod knock. I know the piston does reshape itself as it warms up. That's why a piston has Cam Grind ( being oval) of 1 or 2 thousands.
Also here in the USA we only have 85,87 and 91 (sometime 92 or 93) I'm not sure how they measure it in France but it may be similar octane to ours.
Last edited by guzzi svt; 09-10-2012 at 02:59 PM.
#22
09-10-2012, 03:41 PM
This car (mine, 1998) is made to run with 95 here in europe. It is mentionned in my owner's book if I remember well.
#23
09-12-2012, 11:56 AM
but I am not familar with ...
#25
03-22-2022, 01:45 AM
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Rob
I have 2004 4.2 v8, which rattles, like loose tappets on cold start only.for about 3 seconds. quite loud Rest of time no rattle. My guess is that all the oil seeps to the sump and its a dry start, in the heads.
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