I have a 96 Ranger XLT (3.0 v6) with 78000 miles. It runs best immediately after starting in the morning, but after 10 minutes or so exhibits slightly reduced power and significant pinging under even moderate load. During the first 10 minutes it will not ping even when climbing a steep hill on the way to work.
Ideas on what’s wrong?
Several.
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Carbon build-up causing pre-ignition. The knock sensor is trying to prevent that by retarding the timing, hence loss of power. But, the timing retard has reached it’s limit, and knocking still happening.
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Wrong octane fuel. Try the next higher octane.
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Physical damage to internal parts. If anything got into the cylinders to cause pits or gouges in piston tops or valves, knocking and pinging can occur. This is pretty rare, but does happen.
FIXES: There is a product called ‘Sea-foam’ at most auto parts stores that can help remove carbon build-up. Get two cans. First can, run a vacuum line from the intake manifold vacuum port to the can of Sea-foam, and, with the engine warmed up, let the engine draw in the product as it runs. Follow directions on the can to prevent too much product getting sucked in and bogging out the engine. Put the other can in the gas tank as per directions on the can.
Also, consider running mid-grade or premium fuel for a couple of tanks. This is just to help prevent the pinging until the carbon is significantly reduced.
The engine may be running too lean. This could be from a number of causes: EGR valve open, vacuum leak; incorrect input from the MAF (Mass Air Flow sensor) to the engine computer; inaccurate oxygen sensor; dirty, restrictive, fuel filter; incorrect base timing (excessively advanced); low fuel pressure; other stuff.