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Hey guys first post here, hoping someone can help. So the other day I was driving home from work and out of nowhere my 4Runner started missing. At first if I would put it in reverse it would run fine and I could drive it all the way up the street but as soon as I put it in first it would start to miss fire. Had it towed home and the injectors on cyl 2/4 are not firing, I have power to the injectors and spark at all 4 cylinders. I already swapped the tps, and plugged my ecu into my buddies truck and it ran fine. The AFM tested fine but I don’t know what else it could be. I think I may have a broken wire someplace. With the key on I get 12v at No10 and No20 at the ecu connector when it’s unplugged from the ecu and also at both terminals at the injector connector, is that right?
all four injectors fire at the same time (batch fired), they are connected via splices in the harness. you can test whether the injectors are faulty, or whether the wiring is bad by swapping the injector connectors with each other. it's easiest to swap 2 & 3. if the "miss" stays at 2, the injector is the problem. if the miss moves to 3, suspect the wiring. the factory connectors suck to try to remove with the runner and plenum still attached, because the metal clips are virtually impossible to access.
if the wiring was long enough, you could swap the connector on 1 over to 4. however, you should be able to determine enough by swapping 2 & 3.
my upgraded connector:
the new connectors installed. these are readily disconnected even with everything else in place, and are long enough to be used in any position:
I checked it with a home made NOID light (led) and I’m definitely not getting a injector signal on 2/4. If they are batch fired I am assuming this has to be a wiring issue?
I checked it with a home made NOID light (led) and I’m definitely not getting a injector signal on 2/4. If they are batch fired I am assuming this has to be a wiring issue?
time to break out the multimeter, and pull the sheathing from the injector harness. need to find the broken wire or splice and repair.
I checked it with a home made NOID light (led) and I’m definitely not getting a injector signal on 2/4. If they are batch fired I am assuming this has to be a wiring issue?
Like my signature says, most likely problem with wiring.
There is always 12V on every injector when IG is on. It is the ECU that provides ground to fire them -yes all at the same time via the splices spoken of above and in red below. That splice is in a very inhospitable place so is most likely the culprit.
Originally Posted by wallytoo
... the new connectors installed. these are readily disconnected even with everything else in place, and are long enough to be used in any position:
Wally's update injector harness that facilitates swapping and troubleshooting is nice!
Thank you that is exactly what I needed. Looks like I’ll be going through the harness this weekend.
Originally Posted by RAD4Runner
Like my signature says, most likely problem with wiring.
There is always 12V on every injector when IG is on. It is the ECU that provides ground to fire them -yes all at the same time via the splices spoken of above and in red below. That splice is in a very inhospitable place so is most likely the culprit.
Wally's update injector harness that facilitates swapping and troubleshooting is nice!
Why do you say the injectors are definitely plugged?
Honestly, without testing the circuit, you don't know what is wrong.
Alcohol in the gasoline is the biggest culprit, then you have spoo in the gas itself. Even if it does work it may leak or have a really poor spray pattern. So even if they work "just fine" they may not be just fine and cost in $$$ and excessive wear. Also I did say to check with a noid light, so to me having them cleaned & tested regardless is a step ahead because then you "know" that they all work.
NOW IF i could just find a source for the plastic plugs, I could make up replacement harnesses. As well as the swap harness for the 3.0 to 3.4 swap.
Awesome! Like I always thought, bad connections are more often the cause of issues than defective Toyota parts.
Interesting that the broken splices are on the positive side (blue and yellow wires) when you said, "...I have power to the injectors and spark at all 4 cylinders...."
While you're at it, I suggest you check the splices on the negative side.
Interesting that the broken splices are on the positive side (blue and yellow wires) when you said, "...I have power to the injectors and spark at all 4 cylinders...."
If he was using a multimeter, the connection may have been good enough to show voltage but not good enough to pass the current needed to fire the injectors (assuming the connection wasn't completely broken before he started messing with the wiring). That is just a plausible guess though....
...the connection may have been good enough to show voltage but not good enough to pass the current needed to fire the injectors...:
Yes, Sir; Quite possible. A single strand of wire or even broken wire's barely touching may allow a good voltage reading, but drop voltage once loaded.
Nov 21, 2017 | 01:29 PM
