Alaskataco

I recently bought a 1996 Tacoma V6 4 x 4. I have installed a new water pump, timing belt, tensioner, idler, hoses and belts. I have cleaned the mass air flow sensor as well as the IAC. New plugs and wires. It runs great ....until it stalls. It usually starts right up after stalling but sometimes when I turn the key to the on position the check engine light does not come on. It will not start in this condition. If I wait a while when I turn the key on the check engine light comes on and it starts just fine then stalls again. Both engine grounds are good and I replaced the battery ground to the fender with a larger gauge wire. I swapped the EFI relay with the accessory relay and it acts the same.
There is a clicking sound when it stalls indicating electrical connection problem. I can hear it at the main relay box as well as under the dash. I don't See any arcing. I suspect ignition switch or circuit opening relay.

Janos01

Those could be it. I would also recommend to have the alternator checked to ensure it is regulating proper voltage.

wyoming9

iTrader: (1)

Are you in the habit of having a million keys on your key ring in the ignition switch??

I see this taking out more ignition switches from all the weight hanging on the switch

I had one the weight of the keys would turn the ignition switch off when a hard bump was hit The owner had no clue what was happening

Just what leads up to the engine stalling ??

The noise your hearing is the relay contacts moving .It must be real quiet

Malcolm99

I'd borrow a friends ECU and swap it out to see what happens or inspect it for corrosion, no check engine light when cycling the key sounds fishy, do all of the other dummy lights light up?. I have seen a few runners with windshield leaks dripping on the ECU.

Alaskataco

My keys are heavy, yes but I also have a single key and it acts the same. I removed the ecu and had actually ordered a new one but canceled the order after the Toyota dealer told me that is very rarely the case. It looked great upon visual inspection and all connections tight. I am thinking bad ground somewhere. Does anyone know where the grounds are locate under the dash or other locations?

In response to the question of if all other lights come on when the key is turned, yes they do. Most always the cel comes on as well but sometimes it doesn't. How does one check the ignition switch. Life has taught me that switches and grounds are often the culprits. Did I mention that I also bought a new ignition control module (aka igniter) and it made no difference?

Has to be something simple I think so I want to rule out all the cheap stuff before buying a new ecu. The Toyota service guy said he has only seen 2 fail in all his years and he was not a young guy.

Other options would be perhaps the crank or cam sensors. I think I read somewhere here that they can be tested. Thanks for the replies!

Malcolm99

Well you do have one of the oldest 3.4L ECU's out there so if anyone was going to have an issue with 1 it would be a 1995.5 or 1996, I do agree it is rare in yota's but they are not immune to age, and as soon as you don't see the engine light come on I assume ECU issues or damage to the wiring for one of the 2 diagnostic ports, but your correct to look at the Cam sensor aswell. I've had issues with leaking capacitors with Mitsubishi ECU's before so perhaps my opinion is bias, but the only way to test for a faulty ECU is to try another 1. Is your ECU recording any codes, it would be odd if it didn't since your stalling..

Alaskataco

I think you might be on to something with the diagnostic port wire harness. I thought I heard something from that area and thought plug wires. Any way to test that? Or fix it? Also if you know of anyone with a loaner ecu I would be interested in testing that.....

Alaskataco

Found a used ecu from a 1997 four runner for 40 bucks. I'll try that and report back.

Alaskataco

No codes on the obdII. Had one a while back, egr.

Alaskataco

So I got another ecu and it still acts the same with stalling although now the cel seems to be on every time the key is turned. I am wondering about the coolant temp sensor, has anyone had this cause stalling problems? This wifi probably be the next new part. Maybe iac control also, I cleaned it but did not replace it.

Alaskataco

So i loaded This on a trailer and brought it up to remote Alaska. Not really many mechanics here so I think I am on my own.
The nice thing now is that there is no check engine light when the key is turned. This is what would happen when it would stall and now it is not starting at all.
I have two theories:
1. I see some green dust in the bottom of the fuse box under the hood. There is also a small (2 wire?) connector on the bottom of the fuse box that looks suspect. What is this?
2. Efi circuit opening relay?
Any help is appreciated.

wyoming9

iTrader: (1)

Have you at any time checked the fuel pressure ?? fuel filter??

Weak coil on the Circuit opening relay gets tired contacts open

The ECM ground 3 brown wires should be on the left side of the intake manifold This can cause all sorts of interesting issues of loose or corroded .

Does the stalling have any pattern or is it completely random??

Alaskataco

It used to stall but now the cel won't come on with the key turned and absolutely no start. Really seems electrical. Sounds like maybe circuit opening relay was failing and finally gave up. I have seen different locations, do you know where it is on my 96? Green, right?
Thanks much!

wyoming9

iTrader: (1)

Are you sure the bulb is not burned out or loose in the socket.

The MIL is a simple circuit from the ECM and the gauge fuse

If the bulb is good either the wiring or the ECM is most likely the problem

Did you get water up into the area of the ECM water has taken out a few of mine.

The COR might be in the area below the fuse block on the left side then by 2000 it was moved up and to the right of the fuse block

Should be on the left side just a guess as I don`t have that year EWD

Alaskataco

I think water got in the fuse block under the hood from a prior radiator problem. My plan is to look closely at that box by removing it. There seem to be some brown wires on that single connector under the fuse box bit I can't see it very well.

I did try another ecu and it acted the same. I think the ecu is not communicating. The obd2 can't see it either. Gremlin.

Alaskataco

So the saga continues. Took apart the fuse box and all is tight and bright. I am wondering what the green circuit box on the left side of the kick panel is? (Drivers side) It sounds like a relay clicking when it cuts out. I thought it was the circuit opening relay but it seems larger.

Alaskataco

No closure on this problem but honing in. Seems a bad wiring harness under the dash.