The ECU case may not be grounding properly... You might have a slight leak in the windshield causing moisture/corrosion. Pull the p/s kick panel, remove the ecu, clean all contacts, and chek the case ground.

How did you determine they are not grounding using a test light? Expecially a pulsed ground connection?

I checked the wireing diagram & yes, the injectors have power from the #7 terminal of the ignition switch whenevere it is in start or run position. The ECU grounds them rapidly in very short pulses, so determining if that is happening is going to be difficult.

The computer probably won't ground them at all until the engine is running or at least turning over .

You know you have two vital parts that are testing bad. Replacing them is highly likely to fix your problem. Until those are replaced chasing after other potential problems is really not a good way to go about troubleshooting.

Dave

Well,

Reason #1: I determined that if one connection of the wiring is power the other must be the ground. So positive link to bulb, bulb link to negative connection on injector harness. If I then try to start the motor there should be some kind of blink/glow to say that the wire is grounding out somewhere and fireing that injector. But I got nothing, no circut.

Reason #2: I know I'm not getting ANY FUEL to pass through the injectors, so they must not be firing. If I have the positive comming through I then must be missing the ground. As far as I know the ground wire goes from the injector harness to the ECU, then ECU grounds the wire making it a circut and the injectors fire.

SOOO, I took out the ECU and am going to have it tested to make sure that it is in working order. No since to continue if the ECU is bad.

If the ground wire goes to other places besides the injector, computer, ground please tell me. <img src="/forums/images/graemlins/kewl.gif" alt="" />

While that sounds logical I am not at all sure that the ECU would attempt to fire an injector that had the resistance of a light bulb. It might it might not. If you think about how fast the engine turns even at a slow idle I'm not sure that the bulb would even light up.

Basic troubleshooting methods dictate that when a definite problem is identified, you fix it before going on to other tests. There is no way for you to know how the *known* defective TPS & AFM are messing with your ECU's software. Troubleshooting is a systematic process. You start investigating the most obvious area & fix problems as they are identified until the original problem's gone.It's a tried & true method that works more often than it fails.

Ignoring the defective parts is going to cost you extra time & effort in fixing your rig. It's your call & your time, do what you think will work.

Dave

The ECU grounds the injector signal to STOP firing in rapid succession... The constant ground is through the intake manifold ground wire.

Chase that culprit down first by adding another ground wire to the negative side of the injector harness, and see what happens.

Well i'm not sure about that, the wireing diagram would show the bodies of the injectors being grounded if there was such a "constant ground". That would be a pretty important thing to leave out. Also the injectors are mounted in rubber So any intake manifold ground doesn't affect them. I verified this with a VOM, there is no electrtical connection between the injector body & manifold.

Dave

Check out pg. 13 of Tech Article 22 at http://autoshop101.com/ for a description of how the injectors are powered and grounded.

Yeah that confirms what I expected, the ECU grounds the injector to *fire* it.

It also reminded me that there are resisters in the hot line to the injectors. It wouldn't surprise me if they drop the voltage enough to cause a 12v test light hooked up as described to not light.

Dave

Toyota Trucks--1986 to 95 w/22RE Engine--Intermittent Misfire.

You may run across one of these vehicles with an intermittent misfire that seems to affect some or all cylinders. Your basic diagnostics for ignition reveals nothing, while fuel delivery seems to be OK. It seems that these vehicles have problems with wiring harness splices that are located under the intake plenum on the passenger side of the engine. These splice problems usually result in voltage drops on the power side of the fuel injectors. Unfortunately, only one injector can be accessed without removing the plenum. So, if your diagnostics lead you nowhere, try this tip. First, the upper intake must be removed. Next, unplug all of the injector connectors. Using a test light consisting of a #4651 two-pin headlamp, check for power at the injector power side of the connector. You can do this by grounding one terminal of the headlamp to the battery negative terminal, while connecting the other terminal to the injector connector terminal with either the yellow or blue wire (for 1986 to 1988), or, the black wire with the red stripe (for 1989 to 1995). With the ignition key in the "on" position, the test light should illuminate normally, Be aware, that on the 1986 to 1988 models, the light will illuminate dimmer than normal due to the dropping resistor in the circuit. While the light is illuminated, its a good idea to give the harness a good wiggle. If the light's brightness changes, you've found the source of the intermittent misfire. The light's brightness should remain consistent for all four injectors. If you find one splice that's bad, it's a good practice to open the harness and repair all four, even if they test OK, in order to prevent a comeback. While you have that plenum off, it wouldn't be a bad idea to clean that throttle body.

*Just the article that enlightened me to injectors mis-firing and not firing at all. But what do I know??? My 4Runner's been driving down the road after resoldering all the injector splices....2 years now??

~Darin <img src="/forums/images/graemlins/baby.gif" alt="" />

Sorry for the Lack of updates!

As things have progressed my father and I found out that the ohm meter that we were using went bad <img src="/forums/images/graemlins/angry.gif" alt="" /> It either said that it was open or closed but there were no ohm readings. So upon borrowing a neighbors ohm meter and retested EVERYTHING, we have come to the conclution that ALL the sensors/relays are in perfect working order. We pulled the ECU and tested as many wires from end to end to make sure that there was no separation in the line. All the wires tested good. Of course the ONLY thing that I can't test is the ECU, so I was wondering if anybody has had a bad ECU before? Is so what were the symtomes? Right now I am trying to find someone that will let me test my ECU in their rig to see what happens, possibly vica-verca.



That unit tested fine with ohm meter and passed my inspection with a light bulb. I attached the bulb to the (+) and (-) side of the battery terminals and the light was much more intense at the battery than after the resitor in the injector wire(s).

As a side note there is a simple test you can do to test the Cold Start injector/sensor. Pull off the Brown connector below the T-stat., next to the green connector. With the truck off connect one side to the (+) side of the battery and touch the other side to a bent paper clip that is inserted into the connector. One side will engage the starter and the other will fire the Cold start injector. So just TAP the paper clip, DO NOT ATTACH IT OR THE TRUCK WILL START OR FUEL WILL GO EVERYWHERE! <img src="/forums/images/graemlins/shame.gif" alt="" />

Well I'm off to try and find an ECU to test. Any body in Denver CO, and willing to help send a PM <img src="/forums/images/graemlins/kewl.gif" alt="" />