It must be jumped as the ecu advances timing right off the bat, and that includes at idle. One thing that sticks out here though, is the fact that timing without the jumper was done. Okay, there's a lot of things here that we could look at, now that we have more info on the setup. However, I have driven it with the diagnostics jumper in place, and it made zero difference. Some of the wiring split loom was crispy as potato chips, and I would not be surprised if the knock sensor wiring harness is cooked. This engine overheated before I bought it. Could that cause a problem with connection to the plugs? The wires are one of the first things I replaced, so they have been removed many times. There are no splits in the jackets or boots. ![]() The plug wires are not touching each other anywhere. Idle is a tad high (900-1000), but I was waiting to reset it after the other bugs have been worked out. ![]() I have tested for vacuum leaks but only found two that made zero difference when corrected. The PO did very little to maintain this thing. I'd doubt the coil has ever been replaced at 172K. The timing light was pretty cheap from O'Reilly, but I have not had issues using it on other cars. I am in fact using a dwell/tach meter (it is a decent quality old-school diagnostics unit). I completely forgot to jumper the diagnostics connectors, but all that procedure does is prevent the computer from retarding the timing. ![]() The ECU has never thrown a single code even though the TPS was way out of spec. It revs fine other than the hesitation when accelerating. The engine idles smooth with only the occasional misfire. I raised an eyebrow when I saw the erratic RPMs. Based on research and forum input, I have replaced almost everything (Fuel filter, fuel pump & filter, TPS, plugs, wires, cap, rotor, timing belt & bearings, water pump, distributor, valve shims, PCVs, intake gaskets, EGR valve, etc.). It feels like someone is tapping on the brakes while you try to accelerate. The 4Runner has had a hesitation issue since I bought it.
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