2002 Rav 4 stalls when snap throttle

Hello everyone!

I'm working on a 2002 Toyota Rav 4 that is stalling when I hit the gas all the way down fast. If I don't do it fast, the problem doesn't happen. It has no codes, fuel times are ok, the owner had new A/F sensors and a new fuel pump (motor only). I cleaned the MAF sensor and it did improve a little. I checked for air restrictions on the intake side and it was ok. I still have to check fuel pressure under load. When I pulled the spark plugs, they had oil on them and some of the COPs, so I called it that. The owner hasn't changed the plugs or the grommets but in case that doesn't do it, what else should I look for?? Thanks!

Hey

Fuel pressure and fuel trim data when the engine is under load, at idle, and when you snap the throttle might be helpful.

I suspect you may be on the right track with ignition... Do you have access to a lab scope? I know that these coils were known for intermittently feeding ignition voltage back into the IGF circuit, spiking the PCM and causing the stall. Backprobing the IGF circuit with the scope while reproducing the stall will show if there's an issue.

If you don't have a scope, then you can try unplugging one coil at a time and reproducing the stall. If you can unplug one and NOT get a stall, then I'd suspect that coil has failed.

Like ImBack218 said, some scan data during the stall would also be helpful. Does your scanner maintain communication during the stall?

Fuel trim at idle is normal, and under load is normal, no abnormal ups or downs. When the problem happens, I lose scanner data momentarily and I can't see the the trims...

I do have a small uScope, what does IGF stands for?

I can never remember what igf means. I always remember the igf by saying I got fire and the igt circuit by saying I got trigger. each are a 5 volt square wave.

IGT is the signal from the PCM that triggers the base of the transistor inside the ignition module. IGF is the signal generated by the ignition module that the the PCM expects to see in return.

imanuzz wrote: I do have a small uScope, what does IGF stands for?

I dunno what Toyota calls it, actually. :lol: I always just figured it meant 'IGnition Feedback'. Like Cheryl and ImBack218 were saying, it's the ignition coils feedback to the PCM to say, "Hey, that spark you told me to create? Job's done."

The loss of communication is kinda suspicious, and points to something interfering with the PCM, IMO. We always expect codes to set for IGF circuit issues, but that may not be the case here. :huh:

Your uScope would be great for monitoring the IGF signal during the stall! Here's a wiring diagram of the ignition coils:



I've highlighted the IGF circuit. The IGF is shared between all coils, and ends up turning into one wire that goes into the PCM. The PCM then watches for an IGF 'pulse' every time it commands a coil to fire. If it doesn't see one, it instantly knows something's wrong.

Because all coils are shared across this circuit, it means that you can backprobe ANY red wire at ANY coil, and view the entire circuit. Here's an example of the IGT (in yellow) and the IGF (in green) on a Toyota Avalon, 3.5L V6.



The green trace is missing a downward pulse because one of the ignition coils has failed. Sorry, this is the best example I have in my library, but it gives you an idea of what to look for. Any voltage spikes above 5V, or the signal getting pulled to ground would be cause for concern.

Paul did a fantastic video on this design of ignition coil, DEFINITELY worth watching.

cleaned my idle control valve and sorted the one we had ,full of carbon and oil ?