View Full Version : engine knock

05-08-13, 09:04 PM
I posted before about my engine knock that occurs when it's under "heavy load" going up steep 10% grade hills starting from 0 mph. It seems the most obvious (I can hear it with windows closed and air off) when I am accelerating from 5-10 to get to 25 mph. The RPMs are just below 2,000.

Two things: I am wondering does this cause long term damage? Secondly, if i'm getting the knock at just below 2,000 does that mean it is occurring in every gear as well (I don't hear it at highway speeds)?

05-08-13, 11:33 PM
Has this problem arisen recently? Or has been periodically? Try adding fresh gas to at least remove that variable. Pump 89/91 from a busy gas station to make sure you get fresh gas and see if it goes away. Are you getting any CEL's? How many miles do you have on the car?

05-09-13, 05:58 AM
I have 45,000 miles on it. It's been happening since about 25,000 miles (two years ago). Yes, the dealer told me to try different gas, which didn't help. I had been using regular gas until then and switched to top tier. Also, I had been doing high octane gas once in a while every couple of months. I was doing Techron and tried one other one as after oil changes (every 6,000 miles). I am not getting any CEL's. I did try 91, way back when, it seemed better.

05-10-13, 12:44 PM
You most likely have a problem with your fuel system then if you're having knock. Possibly a fuel injector issue. Either it's leaking when under load when it's fuel and pressure is highest causing fuel to come out before the piston is all the way up causing knock.

Take it to back to the dealer and have them data log or pull the data log they should be able to find which cyclinder is knocking and narrow it down from there.

This shouldn't be a hard problem for a competant mechanic to resolve.

08-21-13, 06:05 AM
argh, I forget about this and now I am out of warranty.

My local oil place switched from Mobil 1 to Pennzoil (I used the Platinum), on the last oil change I asked for Platinum, but they did not tell me they switched to Quaker State (and they proceeded to put in Quaker State without telling me). I also switched to yet another top tier gas station (went from Exxon Mobil to Shell to a different Shell location). My misfire problem is a little better (perhaps after switching to Quaker State). I also did about 1/3 can of Sea Foam in the fuel tank.

C "T" ess
08-21-13, 09:29 AM
To me; It sounds like you are trying to fix a gun shot wound with a band-aid. You certainly tried enough different brands of gas and oil. If you have been having this problem for 20000 miles I think it's safe to eliminate oil and fuel associated problems. Riding with this problem for this long; I'm amazed that you haven't set a code or seen signs of other mechanical problems from the engine. I agree with OMG, I would start with plugs, go onto coil packs and then injectors. If there is no code set, that's about it. The ecm could be bad but that usually sets it's own code. Try going to a local Autozone or such and ask them if they will see if there are any codes set that you hadn't seen.

08-21-13, 11:01 AM
Well, certain things need to be determined: is it a mechanical knock, is it pre-ignition or is it detonation. It may be carbon deposits, low octane or a mechanical problem; since you say it has gotten better (of late), after the addition of Sea Foam, it may in fact be carbon deposits. I would either 'dose' it with a full strength shot of Sea Foam or try a jolt of Chevron's Techron. I am definitely leaning away from the change in engine oil (as both would be compatible together and both meet the requirements for your engine).

09-18-13, 07:18 AM
Instead of changing oils and fuel ...try replacing your plugs and coil packs