Rough idle once warm

I suspect this is a vacuum leak.

There are two things we need to do. First is check for an external vacuum leak using this guide and video:

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

https://youtu.be/4ktw1X4W_-k

Clearly if we find the issue then that needs to be corrected first and foremost.

The next thing we need to do is look for an intake valve leaking or hanging open. That needs to be done with a vacuum gauge hooked to an intake manifold vacuum line.

I am attaching a chart that will help with figuring out if this is an issue.

Lastly we need to check for an exhaust valve issue. This is to be done the old fashion way by holding a dollar bill over the tailpipe when it is running and see if it feels like it is being pulled back into the pipe. If it is then this is an exhaust valve hanging open during the intake stroke and it actually sucks exhaust fumes back into the engine and causes it to run poorly.

Let's start with this stuff and go from there. Thanks

So basically you are removing all the add on systems to improve fuel economy, emissions, and performance and it runs better?

Did you remove them one at a time to see if any of them made more of a difference then another?

Can you get a recording of the engine running? Also do you have a scan tool that can monitor the o2 sensor data? Or let's just monitor the voltage on each sensor while this is running poorly.

Also, these systems are basically different input systems to get the engine to run more efficiently and with lower emissions. So I am thinking that we may have an issue with the sensors telling the PCM that it is running differently then it actually is. You said there is a straight pipe past the o2 sensor which I assume means you have no converter but the o2 sensors are still there?

Great thanks. A quick test would be to just unplug o2 sensor and if the engine runs better then it needs more testing.

Clearly this is not definitive but could be more evidence that we at least have an issue there. That will force the PCM to run off a program and not an actual input data.

Yeah. That second video with the o2 unplugged does seem worse.

How does this drive? Does it have all the power it should have? The only reason I ask, is I am not sure you are going to get it much better. The fact that the bottle stays on the air cleaner (good idea on how to illustrate it by the way), shows that this is just an unstable idle.

However, if you have some performance issues then we are missing something but just not sure what it is at this point.

See what the o2 sensor data is when this is happening would help. Thanks

Okay. So if it is when it starts to get hot then it may be a fuel boiling issue like when they were carb engines. Basically the fuel is not boiling but the air fuel mixture is off at higher temperatures.

So knowing what the o2 sensors are doing would help confirm this. I would expect it to be lean when it is running poorly if this is correct.

So instead of it being a vacuum leak which is more air coming in leaning out the mixture, which is what it acts like, it is the fuel is not sufficient at the higher temp which also leans out the mixture.

Yep. Basically this chart shows the same thing. Overheating is caused by lean misfires or just a lean mixture. So the one that says overheating matches this. You can see on the electrode where you have the signs of it.

So we are on the right path with a fuel starvation issue when the engine is hot. That means we have two paths.

First get the engine temperature down as you stated and it should be fine.

Second, find out why the engine seems to be running hotter. 210 is a bit high.

Do you know what degree thermostat you have in it? Looks like it should be a 190 so you may try a lower degree and the other things you mentioned just to try and keep the engine from getting hotter.

So if everything is hooked up and it doesn't run well but you unhook the EGR and it runs fine?

If so and that EGR is new, was the old one doing the same thing?

Sounds like we may have an issue with the new EGR.

Okay. Holding the throttle wide open is just introducing more air so it sounds like with the EGR hooked up it is running way to rich. A stuck open EGR will cause rough running and stalling at idle.

If it were me, I would take that one back and swap it out for another one then retest.