5vzfe cylinder 4 misfire (1 Viewer)

[fujimori17]

My buddy's 97 4runner threw a cylinder 4 misfire code, p0304. checked the spark plug, has good spark, moved the coil packs around anyway just to be safe, checked the fuel injector with a stethoscope and #4 wasn't ticking like the rest so we figured ok must be a bad injector, we switched it with cylinder 2 injector to see if the problem followed, it didn't, and when we listened to the "new" injector while running it sounded like it wasn't ticking just like the original #4 injector. I tested the plug at the injector with a multimeter and a light bulb. Multimeter said 12v just like the others and light bulb lit up when I touched the POS/neg to the nodes. I have no idea what it could be since the only thing that makes sense would be a weak connection to the Injector but it's pulling the same voltage as the other operational injectors.

Any idea what it could be????

 

[gnob]

Did you check compression

 

[fujimori17]

Did you check compression

Oh yeah sorry I did check compression, 190. Not that.

 

[gnob]

I would double check that driver wire back to the ecm. Make sure its not chaffed or dropping voltage

 

[fujimori17]

I would double check that driver wire back to the ecm. Make sure its not chaffed or dropping voltage

Is there any easy way to do that? The wiring harness is next to Impossible to pull apart. Is that the red or red and black wire? Thanks for your help.

 

[gnob]

At this juncture I suggest a wiring manual.
You should be able to initially sample the wire at the injector and ecu simultaneously.

Basically with injector conn unplugged, the wire that doesn't show voltage is the driver wire.
Sample from there to unplugged ecm conn checking resistance.
At that point with conn still unplugged and ecu conn unplugged, jump the injector conn so you are putting voltage on the driver wire.
Check voltage from the injector plug to ecu plug. This shows voltage drop. Should be zero. I allow generally. 050v. Rule is <.200v

If that checks out, you likely have a damaged ecu

 

[fujimori17]

At this juncture I suggest a wiring manual.
You should be able to initially sample the wire at the injector and ecu simultaneously.

Basically with injector conn unplugged, the wire that doesn't show voltage is the driver wire.
Sample from there to unplugged ecm conn checking resistance.
At that point with conn still unplugged and ecu conn unplugged, jump the injector conn so you are putting voltage on the driver wire.
Check voltage from the injector plug to ecu plug. This shows voltage drop. Should be zero. I allow generally. 050v. Rule is <.200v

If that checks out, you likely have a damaged ecu

 

[fujimori17]

So even though when we checked the voltage at the injector connection and got 12v and were able to light up a small bulb you're saying to run a current through the entire length of the wire one end where the ecu connects and the other end of the driver wire where the injector connects. If the voltage drop is higher than 050 the wire is bad and if there's no voltage drop it must be the ecu?

If it is the ecu is it possible to just swap in a donor from a junkyard or are we going to have to have someone repair the ecu, if so how much does that usually run?

Thanks so much for your help thus far I really appreciate it.

 

[fujimori17]

So just to confirm it looks like E8 pin #7 is the one we want, right? For the #4 cylinder?

 

[fujimori17]

Just realized that this is much different than the 98. Anyone have a pinout for a 98?

 

[fujimori17]

Nvm I'm an idiot and pulled the abs control module

 

[gnob]

You should obviously not have continuity to ground in that wire either.

Got me thinking about what you said about the light at the plug.
You should only be able to light a light at the injector plug if the ecu is firing it

 

[Prairie Swamp]

Injector wiring diagram here:

5VZ-FE wiring diagram

I can't get good resolution on that diagram. Looks like they are ground switched. With the key on there should be battery voltage at the red (?) wire at the injector. There should be continuity (as mentioned very low resistance - far less than an ohm) on the other wire as it goes from injector to the ECU. All the connections need to be able to carry current not just voltage. So I believe you said you replaced the injector with a test light? With the motor running the light that replaced the injector in question should be glowing? I wouldn't use a headlamp bulb but more like your basic automotive test light.

If the wiring checks out sounds like the ECU might not be able to ground or carry the current necessary to run the injector.

As far as a replacement ECU - I'm going to say it would have to be from the same year, engine and transmission to be safe.