Best of Deals Car Reviews Repair Shops Cars A-Z Radio Show

Engine Additives

I have a 1991 Jeep Wrangler 4.0 with almost 200k miles. There has been a tapping noise coming from the engine that I am sure it is caused by carbon buildup on the valves/lifters.

Is there an aditive that I can use that is better than others to remedy this? I know that there are numerous products marketed to clean injectors and remove carbon build-up, but which one works best?

Also, I have heard that if I run the engine at a high RPM for approximately 10 minutes it will help to remove the carbon deposits. Will driving this way harm my engine/transmission?

Why do you say it’s carbon?? This engine has a history of tappet problems.

I also wonder why you suspect carbon buildup. Unless the “tapping” is actually pinging, the symptoms are not typical of carbon buildup symptoms. Even if it were pinging I’d suspect other things first.

Can you elaborate?

It’s not carbon deposits.
If it’s any kind of deposit it’s varnish deposits in the valve lifters.
Something like Marvel Mystery Oil or such in the oil may clear it out.
Or maybe have the lifters removed and cleaned in solvent.
Or new lifters…