1996 V6 5VZ-FE engine bogs to stalling when warm

Hey, I'm having an interesting issue with my Tacoma. It's a 1996 v6 with the 5vz engine, and an automatic. The car will start up fine, and idle fine. Once it gets warm though, the engine will sputter a bit, and the idle gets rougher. While driving, the throttle can become unresponsive, and the truck will buck. I've been doing a bunch of maintenance on the truck that was needed anyway in an attempt to track down the culprit, but the following has had no effect:

• New spark plugs/wires when I first got the truck
• Timing belt and water pump
• MAF sensor
• TPS
• Fuel Filter

Anyone has any idea as to what may be causing the issue? The engine will throw a CEL when it bogs down, but the next time i try and start it up it's gone. Another interesting issue is that when I have an OBD reader connected, monitoring a few items, when it bogs down the OBD port stops sending data or the reader otherwise disconnects, so it's impossible to tell what's changed.

There have been a couple of suggestions from others thus far, but I'm unsure how to tell which it actually is:

• Catalytic Converter
• Fuel Injectors
• Fuel pump

 

How long do you wait before it runs normal again?

 

Usually it'll start right back up, but will start to run choppy almost immediately. After letting it cool down it does the same thing. Runs fine for 10 mins or so until it gets warm and then starts to bog.

 

I had a v-6 camry that did something similar. It ran fine, but as soon as the check engine light came on, I lost communication with the scan tool and it would run bad. Get the engine ecu out where you can unplug it and pull it out of the truck, but leave it plugged in. Let it warm up till it goes to running bad and you lose communication with it. At that point, kill the truck and put the engine ecu in the freezer for 5 to 10 minutes. Then throw it back into the truck and see if it will run properly and communicate with the scan tool.

 

Editing to add a few videos of what happens:

https://imgur.com/KV607mk

https://imgur.com/B5Oz9Vb

https://imgur.com/xGtWQFW

 

How long has this been an issue?

When the engine is cold The OBD system works normal?? You never have any stored codes after your issue occurs ?

Your OBD device works correct on other vehicles as to rule out that being a problem.

My first step would be check out your ECM Ground!

Engine gets warm the ground connection gets loose.

This tells me you have a ECM issue . That your OBD signal is dropping out.

Did Your ECM get very wet or have a voltage spike??

Nasty Rodents chewing wires?

Best of luck!

 

How long has this been an issue?
Since before I did any of the work on the truck - most of a year, and it's been pretty much sitting since as I try and find time to chase the issue.

When the engine is cold The OBD system works normal?? You never have any stored codes after your issue occurs ?
Yes as soon as it cools down the OBD works as normal. And if I'm live-monitoring certain metrics when it starts, the data stream just stops

Your OBD device works correct on other vehicles as to rule out that being a problem.
Yep, confirmed in other cars

My first step would be check out your ECM Ground!
This will be fun to chase, i will look into how to test this one.

Engine gets warm the ground connection gets loose.

This tells me you have a ECM issue . That your OBD signal is dropping out.

Did Your ECM get very wet or have a voltage spike??
Not that i know of! ECM is in the glove box right?

Nasty Rodents chewing wires?
Hopefully not, but we shall see!

 

Did you try the freezer trick?

 

I have not! I will try again though to see if that helps. I actually didn't think that was really a thing, I couldn't find any other sources for that googling it.

 

It doesn’t happen often but I have seen it. Another strange thing I have seen is when an alternator allows A/C voltage into the vehicles electrical system. That causes very strange running conditions. In my nearly 30 years of working on cars, i’ve only seen it twice. Once on a chevy and once on a Tacoma.

 

Could be the electronic ignition igniter. Or sometimes referred to as the ignition control module check all the wires make sure nothings frayed or barely making connection and check grounds.

 

Coolant temp sensor can cause funky behavior if it runs OK at some temps but not others.

I had one do the opposite. Truck was a bitch to start and keep running when cold but would run great all day if you could get it to warm up

 

Here’s a photo I found on this website that shows the location of the ignition control module

 

Ok great I will check this out as well - That looks like its attached to the MAF sensor, is that true or is it just the angle?

 

I did also find this other threat about general ECU/ECM problems that sound very similar to the issues I'm having:
https://www.tacomaworld.com/threads/1996-tacoma-ecm-stops-communicating.532116/

They also recommend using the OBD1 port in the engine bay to get CEL codes, which I may give a shot as well.

So when I get some time I'm going to try the freezer trick, and I will report back when I have an update on that.
The thing that has me scratching my head is that everything works fine UNTIL it gets up to temp, that and the additional clicking noise that you can see in my third video above.

 

Ive never seen the transmission shifter in the steering column before

 

Yeah unfortunately this guy is a 96 2WD base model extended cab, not fancy enough for that floor shifter.

 

It’s just the angle. It should be attached to the fender has a group of wires going to it.

 

Try this just to see, let it warm up till it starts acting weird. Shut it off and unplug the alternator 4 pin connector. (might be 3 pin). Do NOT take the 10mm nut off the big wire that is the charging wire that is on the alternator. Crank the truck and let it run. The battery light will be on but I’m curious to see if the bad running stops. If it does, while the truck is running,plug the alternator in and if the problem returns. I listened to your last video and it sounds like the alternator was whining.

 

I had a 96 extended cab just like it that I sold to my stepdad and he still drives it… I’m trying to buy it back but he won’t part with it, hence the reason why I bought the 97 I have now..