4.0 IGF Circuit issues.

My 2007 4.0 died on me a couple weeks ago. Thanks to this forum, I diagnosed it as a failed coil. I went through each one measuring the voltage on the IGF circuit until I found the one making the voltage drop to 2v. Replaced that coil, and the truck fired right up. I drove it around for about 20 minutes and all was good. Later that evening, I headed out to grab a bite to eat and the truck died again. Went through the process to check the IGF Circuit and found a different coil had now gone bad. The Coils are NGK's replaced about 18 months ago. I have a new set of Denso's, but I'd like to know if there might be some underlying issue causing the coils to short out before I burn through any more.

Thanks,
Mike

Edit to add that the problem started after changing out the spark plugs. I used the OEM Denso plugs.

 

Haven't really seen any issues with Toyota OEM Denso coils going bad even when people run them with worn out or incorrect plugs, aftermarket ones though seem to be hit or miss. That's why I never recommend changing them as a maintenance item, they do fail occasionally but not very often.

If they came from Amazon/ebay all bets are off, you may get a genuine part but alot of stuff on there is counterfeit or just outright garbage.

 

Thanks for the reply. The coils did come from Amazon, and I had read here that people were having problems with them. I ordered the new Denso coils from RockAuto, so hopefully that will fix the issue. Just wanted to make sure I wasn't overlooking something.

Thanks,
Mike

 

I've yet to see an OEM one fail in a way that takes down the IGF circuit but that seems to be a common failure mode of alot of the cheap/knockoff ones.

The OE coils typicaly just quit producing a spark when they fail.

I have seen where a few people had water get into the J12 connector under the PCM and take down the IGF circuit but if that were the case you wouldn't be fixing it by swapping coils.

 

Thank you sir.
Mike