Unplug EGR Valve

Are you saying you can run the car with egr unplugged and you don’t get the cel symbol coming on? Could you explain the process in detail?

 

people just ignore it /

 

It also retards the ignition timing.

 

I don't want a retarded Prius.

moto g power ?

 

Driving around with the timing constantly retarded is a kind of a "limp mode effect", just maybe not severe enough that you notice it.

 

It would seem this whole discussion is purely academic if the cooler was 100% plugged anyway. Unless the real issue is a leaky egr valve at low rpms which causes a bad idle or misfire and perhaps gets mechanically sealed off by the owner. We know the egr valve should be closed at startup and low engine power.

 

I have a question about Disabling the EGR valve: If my engine gives me rough shuddering accelerations when starting from a stop, but it runs smooth at driving speed, and if I disable the EGR by unplugging the harness and then the engine runs smoothly in all conditions, does that mean that there is nothing wrong with my head gasket? Forgot to state that I have a 2014 Prius V with 162000 miles and have never had a problem with it until the rough acceleration thing started a couple months ago.

 

A better test is to block the egr tube from the valve to the intake. If the egr is not working or leaking it will allow exhaust into the intake regardless of the electrical. Also aftermarket egr valves are known to stick open.


Car Care Nut video with egr block tube test

Rough shuddering is more commonly a leaking head gasket on these engines but blocking the egr can remove egr from the list. Don’t waste your money on plugs, coils or injectors when the issue goes away quickly as you describe.

 

Thanks for the reply and the video link. I had watched that before but wasnt sure about running with a spatula in place. So if I block the EGR with a spatula and the problem goes away we can conclude that it is NOT a head gasket?
One other detail here is that if I open the cap on the coolant reservoir in the morning after it sits all night I have a good puff of pressure blowing out the exit tube..

 

Yes - after a couple of weeks. We have seen people change plugs and the symptoms go away for a short time. Others loosen up the reservoir cap and eliminate symptoms for weeks. Meanwhile an underlying hg gets worse in many cases and that’s not good if it costs an engine.

A quality dual view borescope when cold with pumped up coolant pressure is the most definitive test from a hg fail standpoint on this engine.

Car Care Nut HG Borescope at 7:40

 

Thank you for adding that video. I have not seen that one before.

 

If the egr is sticking open or jammed open you get a stumbling engine.

When the normally closed egr at low rpm is allowing flow it fouls the air fuel mixture. Blocking is a test for this situation.

A clogged egr cooler won’t cause stumbling or severe hg shaking.

 

It's pretty well agreed here that clogging at the manifold causes that; there are four separate passages that can get differently clogged, leading to different EGR % in different cylinders, and the car can't detect and protect against it because there is only one MAP sensor.

Where opinions differ more here is where only upstream clogging, say at the cooler, is involved.

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