I have a 2.5 ranger 135,000 miles that i recently changed the timing belt myself. I did everything by the book. On the first start it had a horrible noise for a max of maybe 2 seconds almost like a rod knocking. Then after that the really bad noise it was reduced to a tapping sound. I then turned the engine off. This whole process happened in about 10 seconds. I let it sit a minute scared i just really screwed up my motor. Then i cranked it up again, no really bad noise this time but it still had the tapping noise. I let it run this time for about a minute, did not improve any. I then let it sit for about 15 minutes and got a stethescope to hear where it was coming from. But this time when i cranked it, Nothing, it ran PERFECT. I also replaced the exhaust side plugs(origanal). The only thing i could figure is that for some reason the computer was running the timing really advanced and that was where the knock was coming from??? it runs perfect now so i'm not that worried about it i was just wondering if someone had an awnser to what happend or if anyone else has seen this....

Thank you for your time...

 

Your engine is probably just fine. I had that exact same sound like rod knocking. It will likely come back again. Your belt is probably not tensioned quite enough. When you install the belt, make sure everything is aligned correctly for the crank, cams etc, and then with the tensioner loosened enough to take up slack under its own spring power (should have a powerful spring against a pin to keep it pressing on the belt), turn the engine over a couple times the normal direction. Make sure the tensioner can move freely enough to take up any slack as you rotate the belt. Then tighten down the tensioner pinch screw to the block to hold that tension. I would advise against adding much more than the spring provides alone because it will wear out the bearings and destroy the tensioner quickly. That accounts for any slight amount to play among the cam sprokets in the belt because even a few milimeters of play can cause enough deflection to slap the belt cover and make that awful "knocking" sound. If it still knocks, add a tiny amount of additional presure to the tensioner before tightening it down, keeping in mind that increased bearing wear could result from too much tension (I know because I did that!) Good Luck.

 

Did you replace with the same spark plugs?
Its always a good habit to compare (side by side) the plugs, especially the thread depth and where the shoulder/seat is on the threads to the tip of electrode.

The last time i got spark plugs for my ranger,(this spring) i got a set of Champions that would have protruded about a 3/16'' longer (more thread, i compared when i took the first one out of truck) i took them back, and ordered another set of 8 Autolites (i prefer) that i have ran for the last 90-100K miles.

Also always double/triple check the timing marks on the sprockets for alignment when changing the belt.