I have a 1997 ford ranger 2.3 5 speed, i bought it was 170k miles and have owned it for a year I'm at about 190,000 miles currently. Lets start with the first problem i had: I was driving home from work one night and shifted into 3rd and the truck stalled, got it back home found out it jumped time. we replaced the timing chain along with water pump, surp belt, thermostat, other misc. things. I drove it for about month then was recommended to change my plugs (although they were fairly new) i bought motocraft plugs and when i replaced them i noticed that the 4 on the drivers side (intake) were fouled and dark, while the 4 on the passenger side were clean and looked brand new. I replaced the plugs and drove it for awhile and thats when i started noticing the pinging. the CEL flashed for a cylinder 3 misfire and lean bank 1, insufficient ear flow, and heater circuit 1 malfunction (upstream 02 sensor) , i had about 4 codes. Well i figured i screwed up putting the plugs in no big deal so i changed them again this time being more careful and the misfire code went away but the lean fuel and the heater circuit 1 malfunction code were still there. i did a few things to try and fix it i replaced pcv valve, cleaned MAF, new air filter. new IAC valve. and i got the lean fuel mixture code to go aways some how. anyways i was driving it all summer and never had spark knock unless i would actually put the pedal to the floor. I could keep at it about 70 mph on the highway which as fast as i needed to go so perfect. i recently changed the 02 sensor thinking that would take away pinging entirely since the sensor may be causing it to run lean and knock. I was driving it for a day or so and the CEL came back on, for a canister purge valve. well i replaced that no big deal and then it came back on later for a canister purge valve solenoid malfunction, apparently they are two different things. well i haven't gotten around to changing that yet but the CEL will come on and off depends on the day, currently as of tonight my CEL is off but when i was driving today the pinging was worse than ever, i could barely go above 60 on the highway and no CEL the whole time i was driving with almost constant pinging. i know this is bad for an engine but i have to take the highway and go highway speeds but now my truck won't allow me. there are a few things i think it can be: 1. EGR valve is still messed up perhaps carbon filled (the EGR code is gone) i fixed the vacuum lines on it and this makes sense because this opens when the engine is under load, like when I'm on the highway. 2. Carbon in the engine. When we pulled plug 1 when we were doing the timing chain we noticed buildup of carbon on piston. this engine has 190k miles to me i know there has to be a lot of carbon in there. 3. Timing is off slightly, this is kind of hard to believe but I've noticed this being the solution to a problem like mine before. when we did it we thought we had the ticks lined up but i may have made a mistake. 4. weak fuel pressure. or weak fuel pump. this seems likely, my engine did have a lean code (it does not anymore its been gone for a few months) another thing to add to this, tonight before i noticed how bad the pinging was, i took my MAF off and cleaned it tonight, when i started driving it the pinging was much worse. so I'm guessing its getting good air flow but not sufficient fuel ? I'm at a loss and it can really be all things. just wanted to see if anyone had suggestions. i was going to seafoam my engine. if that didn't work i may replace egr valve or maybe injectors, fuel pump, or fuel filter. I'm puzzled any input would be appreciated .