tom h

I have searched this forum and have not found anything like this. Any help will be appreciated.

I have a 1994 Mazda/Ranger with a 3liter engine, automatic transmission, 2wd, towing package, 185,000 miles and generally it runs great.

I commute 22 miles to work and when I stop at an intersection 14 miles into the trip and then even with light acceleration the truck knocks severly and a cloud of light smoke comes out of the exhaust. It will not knock or smoke after this point even with full acceleration. I have tried slowing down before this intersection and accelerating and it will not knock or smoke until I have driven about 10 miles. At this point I can accelerate twice and it knocks and smokes and then it will not knock or smoke again.

To simplify, it will not knock or smoke until I have driven about 10 miles. If I slow down and accelerate twice it knocks and smokes and will not do it again. If I stop once and then accelerate it knocks and smokes worse and will not do it again. If I stop the truck and turn it off before it knocks and smokes and then crank and continue the trip it will not knock and smoke.

I have had the cooling system pressure checked hot and cold to check for a blown head gasket.

If you have any questions, let me know.

Thanks

atec77

Have you tried altering the grade of fuel ?

tom h

Yes, I run 89 octane, but it does not help the intermitten knocking.

atec77

Not much help I am afriad apart from knowing you will most likly have a bad sensor , have you checked for codes ?

tom h

I was told by my mechanic that in 94 the codes are not helpful.

Thanks
Tom

pillen140

is the stop light by any chance down hill? or is it a quick stop? could be the oil pump, that would explain the knocking but the smoking i have no idea. i had that problem with a thunderbird 3.8 when he hit the brakes hard the oil would go forward leaving the pump dry, thus knocking. no idea for sure though.