Knocking - Toyota Nation Forum : Toyota Car and Truck Forums

suprabran · 09-04-2009, 08:47 PM

This is pretty weird so I wanted to ask. The supra drives great once started and it runs fine till I turn it off. Once it sits for maybe 10 minutes and I crank it up again, it will knock for a minute to a minute in a half it has never done this before. What could be wrong? If it sits for 30 minutes or longer it starts fine with no knocking.

Jeeves · 09-08-2009, 06:34 PM

I'm assuming you've checked your oil levels?

suprabran · 09-09-2009, 07:18 AM

Yeah level is okay and the oil is changed.

Jeeves · 09-10-2009, 10:18 AM

Can't say I've heard of a situation like this.
Is it actually knocking? As in does it increase rate with RPM? Can you use an automotive stethoscope (or long screwdriver, or other long metal object) to confirm it's actually knocking?

suprabran · 09-10-2009, 10:57 AM

It increases with rpm, as for knocking I have a diesel Mercedes it sounds like the diesel just for that little time. Is this knocking if it sounds like a diesel engine? I thought that was knocking but I could be wrong.

Jeeves · 09-10-2009, 02:04 PM

Knocking is a metal on metal sound caused by a bent connecting rod inside the engine hitting metal usually means failure is imminent.

You Tube

You Tube

You might be hearing pinging from compression and heat soak? Try upping the octane level of the fuel you're putting in?

SupraTuned · 09-10-2009, 04:42 PM

Wow, that second vid is absolutely terrible. Supraban, have you tried checking if you have a dead cylinder? This can sometimes sound like knocking if it isn't firing properly. Also, make sure you didn't put in too long of reach spark plugs. Sometimes they are not boxed correctly or the auto store gives you the wrong ones. I always double check. I have seen that one before and I did laugh accidentally and kind of pissed the guy off. But jeeves brings up a good point with the octane, you really shouldnt run anything but premium in the 7m. I run 93, sometimes 94 from shell and it runs amazing. Main thing with them is they don't put ethanol in their premium. This may not be true everywhere though. It may be a little more expensive up front, but the return is well worth it.

suprabran · 09-10-2009, 10:09 PM

I only put 93 octane fuel in nothing lower. It might be a dead cylinder, would you have to compression check it? I put new plugs in a year ago NGK V power and I made sure the gap was fine, but I never changed the rotor or cap could that be something wrong with it?

suprabran · 09-10-2009, 10:13 PM

I just watched the videos Jeeves, thanks for them it really helped out with knowing what knock is. It actually sounds like the corolla engine at the top when it does it. It is for a brief minute when cranked up, but then goes away.

Jeeves · 09-11-2009, 10:01 AM

Well, we don't have lifters which is what most unknowing people would blame a fresh start ticking sound on (typically called lifter tick) but I'm forced to look at the things that would be different from a 10minute sit versus a 30minute sit and generally all I can come up with is less time for heat to disspate (higher underhood temps) which equates roughly to heat soak. It's notorious for causing poor performance and rich running (because the fuel calcs are off) in such a condition, but knocking doesn't come and go. Knocking is a mechanical condition.