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EGR error code and weird hesitation

gingerdude

gingerdude

Donating Users
Recently started getting P0406. Did the typical EGR unplug and reset procedure, which usually gets rid of it, but it keeps coming back. Likely carboned up this time.

Around the same time I noticed a weird hesitation only at a certain pedal location. Feels like a heavy misfire. Seems to happen regardless of transmission gear when I just barely push the pedal to keep moving. Below and above this spot on the pedal everything is fine.

Going to get my scan tool and investigate further when I have a chance. Could the EGR issue cause this? TPS? IAC?

Edit: Updated to proper code.
 


Not sure, but maybe the egr pipe is cracked and you have a nasty vac leak? If you are slowly getting on the gas when your engine acts up, and you have some big vac leaks, you could get misfires at that throttle because the converter isn't unlocked yet and you are running lean. How is your idle?


EDIT! Yes, I am editing my post because I can't even remember the last time I was able to. I have nothing to add though.Sorry
 
The idle is smooth most of the time, but choppy others. It's been like that since I got the car. Seems to be choppy when it's warmed up after driving for awhile. Say I make a long drive on the interstate, stop to get food, restart, it's choppy. I've rebuilt the engine from the head gaskets up, and it's still the same. I have given up on that tbh.

I'll check out that pipe again. Last time I checked over it the best I could and it seemed fine, but I might just have to pull it off the car and look at it in my hand.

Wouldn't a stuck open EGR due to being carboned up cause what is essentially a vacuum leak?
 
So the idle is normal? Think stock is 650ish in gear. When your car sits after it was ran for awhile, it will heat soak. This will cause you to be a little leaner when you restart after it sat for a little while. Only takes a couple minutes of moving to cool things back down. So, if you have a vac leak on top of that, you will be running pretty lean for a few minutes which is probably why the car idles rough at first.

EGR is only recirculating exhaust gas into the intake. It's metered air. Only a cracked egr pipe would cause a vac leak.
 
Idle is around 700 in gear. I reset the computer with a battery pull to see if the light would go away. I know sometimes these EGR valves can be finnicky.

It came back, same code. When I get access to a garage I will pull the EGR off and clean it out. I will also investigate that tube for cracks.

Definitely tons of misfires when that hesitation happens. They just stack up when it does. But it only happens rarely and only when the car is first warming up.

I will investigate for a leak again.
 


Replaced the EGR under the parts warranty.

I pulled the EGR tube off the manifold. No cracks or issues so I reinstalled.

Seems to have solved the problem.
 
I'm going to be lazy about looking up codes since you only listed the numbers.

If either was egr flow.. you should be checking the map sensor. Because while the code for EGR insufficient flow seems to point you at EGR. Often it is the map sensor not reading a change in pressure.
 
I haven't had the "sustained misfire while at low throttle with engine cold" since I swapped.

But if it happens again I will definitely investigate that. What other symptoms should I look out for if this is the case?
 
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