My friend's 4 cylinder 1998 Rav4 is knocking when going up hills on the highway. There's nothing else obviously wrong, and no warning lights.
What could be the problem? Could something be wrong with the knock sensor?
Jimmy
Crappy gas?
Bad/old plugs. ;)
Bad gas. ;)
Use a higher grade of gas, and add Chevorn Techron to one or two tanks. This sounds like pre-ignition knock.
My friend thinks the plugs were changed during scheduled maintenance. But that is something to check, since I know from experience that asking for a standard scheduled maintenance can result in a wide variety of things getting done or not done.
The manual says to use 87 octane. I'd think if a higher grade gas is required to prevent knocking, it means something is wrong with the engine, which it would make sense to fix.
Jimmy
The combustions chambers are collecting carbon deposits, at the top of the cylinder head, which raises the compression of the engine. Higher compression usually requires higher octane.
Now, the ECU with the knock sensor are supposed to compensate for this, but it appears they cant. I would jump to the next higher octane level, or even up to 91/93, and use Chevron since it already has Techron in it. If not, get a couple bottles of Techron and run them through the engine according to directions.
My '85 Corolla GTS started doing this back in 1991 or so, even though I always used 91/93 octane. BTW, in the long run, using higher octane cost me , because fuel economy improved by ~4MPG. I used Techron over a course of a few weeks, and the knock went away, never to return again.
I would also change fuel brands.
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