4Runner J

I took my 91 3VZE 4Runner into my local mechanic to get an oil change. My CEL had been on for a couple of months. I new it was the O2 sensor, so I had him install a new one. Now the truck won't start. We did manage to get it started once, but I think the mechanic sprayed some kind of combustible into the throttle body or something. The hood was up and I was in the truck, so I couldn't see. It started and ran for a while, but I had to keep my foot on the throttle otherwise the RPM would drop rapidly and it would stall. When it started, the RPM was jumping up and down like a yo-yo unless I applied more throttle and raised the rpm pretty high. Before I brought the truck in for service, it ran great. I had the engine swapped 5 months ago and since then it's run like a charm. No trouble starting or anything other problems. Does anyone have any ideas for me to try? I think it might be an electrical problem as the wiring on my truck is not the best.

WILLTHISIFSGOHIGHER

Yea could be, I know my 92 runner is cutting out when I go over bumps in the road at speed. I think it is a shorted out wire or sumthin. But it sounds like you could have something similar. the hard part is figuring out which wire it is. Good luck

low-n-slo

try putting the old o2 sensor back in and see if it works

sb5walker

What kind of O2 sensor did you get? A direct-fit Denso or NGK/NTK I hope. If not, was it at least a direct-fit? If it was a universal, then the mechanic had to manually splice wires, and he probably screwed it up and crossed some wires. Hopefully didn't permanently damage your ecu. You can at least test for a good heater in the sensor by checking resistance on the two wires of the same color (on the sensor). See the fsm for the spec.

Try pulling codes, if something was left disconnected there will probably be a code.

Sounds like no gas. Check for power on terminal FP in the check connector when someone is cranking the motor. If no power, make sure there's power on +B when ignition is on. If no, check EFI fuse on passenger inner fender, and IGN fuse in drivers kick. If the fuses are good and no power on +B, probably either bad EFI Main Relay or bad ignition switch. (If IGN fuse has no power when ignition on, then probably bad ignition switch (or connection to/from it); if IGN fuse has power, prob bad EFI main relay.)

If power on +B but not FP when motor being cranked, either bad circuit opening relay, or bad connection from starter relay (MT) or neutral start switch (AT) to the circuit opening relay (black wire white stripe - should be hot when ignition switch in start position), or possibly bad connection from COR to term FP and pump (blue wire) or bad COR ground (white wire black stripe). If there is power on FP when cranking, have someone listen at the gas tank when someone else cranks it. You should hear the pump begin to run as the motor starts to turn over. If motor starts but then quickly stalls, could be bad fuel pump switch in air meter (see VAFM section in fsm) or bad connection to the air meter (you'd get codes if that were the case, tho.)

If pump is running okay, check for spark. If no spark, check for power on positive terminal of ignition coil when ignition is on. If no power, either bad ignition switch or bad connection - maybe a blown fusible link or broken connection somewhere.

If no spark but there IS power to the coil, most likely bad coil, possibly bad igniter or bad connection or blown signal coil in the distrib, or bad connection TO the signal coil. To check the ignition coil, make sure ignition off & disconnect all wires to coil. Between positive & neg terminals of coil should be .4 to .5 ohms (that's right - about half an ohm). Between positive terminal and high tension terminal (where cable attaches) should be between 10,200 - 13,800 ohms (10.2k -13.8k ohms) COLD. Unfortunately it's possible for a coil to pass this test but still be bad. But it's not real common.

Check the resistance of all three signal coils in the distrib: they should all be 140-180 ohms cold. The green wire in the harness is the common (neg). Check for resistance between that and each of the others. (Of course, check on the wires that lead to the distrib.) Air gap between the signal rotor lobes and the signal coil projections should be .2 - .4 mm (0.008 - 0.016 in). Also try wiggling the distrib shaft side-to-side. There should be almost no movement.

Check that terminal E1 on ecu has a good connection to the chassis, terminals E01 and E02 connect to the engine, and both engine and chassis have good connections with neg batt post. Make sure body of igniter has good connection to chassis ground.

Good luck.

When you've settled the current issue, perhaps find a different mechanic?

4Runner J

The new O2 sensor is an NTK by NGK. My mechanic says that he fixed the problem. Turned out to be a bad ground. Not surprised. I had another ground issue before. I really appreciate your help. Especially sb5walker, as it must have taken some time for you to write all of that info up. Cheers.