My 1990 4Runner has run like a clock for years. Some light 'chugging' started to occur a few weeks back - when driving along it just feels like it misses on occassion, loses power for a second. It seemed to me like it was an electrical problem of some kind (plugs, wires or something). I replaced the plugs but the problem persisted. The last 2 mornings (first thing) it has been really bad. Took to the Toyota dealer who informed me it was the plugs (that I had put the wrong ones in). I informed them that the problem existed before I replace the plugs. I asked them if it might be the wires, they didn't think so. They did what they called an idle test and said it was running fine (not sure if they actually took it for a drive). Nevertheless, I changed the plugs again to the Toyota ones. Problem still persists. What would people suggest I check for next.

 

what engine?

 

Timing maybe?

 

It is a 4cyl manual

 

Resolved the situation - changed ignition wires (NGK). Runs great now. Funny thing is that the Toyota dealer didn't think it was the ignition wires.