My 1994 Toyota 4Runner 3.0 6VZE with 4speed automatic transmission is really rough at idle (almost cuts out). It also runs rough at slow speeds, less than 10 mph. It accelerates slowly up to 45mph and has a noticeable shudder or misfire in the engine. The check engine light and O/D light have not come on. I drove it home and parked it rather than taking it on the highway. I checked the engine oil, transmission fluid, power steering, brake fluid, and engine coolant (radiator). All fluids are full and new looking. There are no leaks and there are no smells. I did not see any wiring damage, like from rats. The drive shaft isn't loose or floppy. I jumpered pins E1 and TE1 on the diagnostic test panel by the fuse box in the engine bay and turned the ignition on, but not the engine. I get constant flashing 'Check Engine' and 'O/D' lights, but there is no pause. Does this mean there are no codes? Where should I start troubleshooting? Should I suspect an ignition problem? Could it be bad fuel? (I just fueled it before the trouble showed up. The tank is still full.) Could it be a bad piston? It has less than 2,000 miles on a rebuilt Jasper engine that was installed by a reputable shop locally, just over a year ago. It is just out of warranty.
When I could be tons of things but unfortunately it's so old it is extremely hard to get any kind of actual data out of the car. Rather than guess you're better off paying a guy like me who has an old dealer level scanner that can get there to even out of that old thing. It could be dirty fuel injectors a failing ignition system lots of things but the data has to be analyzed and only a really good Toyota mechanic can do that
