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Carbon knock in Ford 4.0 L Warren 12-11-02  
Ford has a TSB for "carbon knock". It occurs under light accelleration from 20 to 40 mph for 10 to 15 min while warming up. No noise when the engine is hot. The TSB says to pour Ford carb cleaner in the intake at idle, let it sit for an hour, do it again, let it sit for 15 min and drive to burn it out. It works...no noise for a few days then the carbon knock starts to return. It seems worse the morning after being on the freeway for 50 or 100 miles or more. It sounds like a single knock, like one cylinder, but I don't know which one. If I did, I would put a hotter plug in that hole. This is apparently unique to the 4.0L. The engine has 85k on it and uses about a quart in 1,200 to 1,400 miles or so.
Any ideas on determining which cylinder? How to eliminate it? Any help is very much appreciated, and thank you in advance.
Re: Carbon knock in Ford 4.0 L Joe 12-11-02  
Well, GM has a carbon blaster also that I have seen work well. If you are sure that carbon is your problem, you might try that. Way way back when I first started mechanicing around with my $39.95 box of Crafstman tools, we didn't have the modern cures for these problems. We used black pepper for stop leak and plain water to blast carbon off the tops of the pistons. Water was almost free, and black pepper was $.39 for a can big enough to do 20 radiators. So now you can spend $12.95 for a can of carbon blaster or find a 16 oz cup and fill it with water. With the engine racing at 1200 to 1500 rpm slowly pour the water into the air intake not enough to kill the engine. If you pour it too fast you could cause a hydrostatic lock and bend or brake something as well as pollute your engine oil. Or take the heads off and do it properly, as whatever you do other than that the problem will return. Good luck.
Re: Carbon knock in Ford 4.0 L Kenneth W. Vayda 3-5-03  
Check the torque on the intake manifold bolts. Have seen several loose causing the engine to suck oil from the bottom of the intake port, causing pinging and oil usage. In the two that I have recently seen, both started pinging and using oil at around 75,000 miles. By the time one had a 100,000 miles, it was using a quart every 500 to 600 miles. After retorqueing intake manifold (follow ford recommendations)it has now been driven 2500 miles and no oil usage. Pinging (carbon knock) has also stopped (90% of it). Good Luck
Ford ranger timing chain guides Dave 1-3-05  
My 2001 ranger has rattling on start up and loud rattling under hard excelleration until tranny shifts out of lower/passing gear. Is this my timing chain guides and how many hours labour. p.s I've tried higher octane gas.....thanks
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