Suzuki Swift stalling and EGR codes. P0401

I've just moved across the country and started a new job. I took on this particular job because I enjoy
a challenge - This 2007 1.3 GA Suzuki Swift has been giving the company headaches for 3 months now.
Occasionally it idles really rough and once after driving 90km the owner stopped and re-fueled and the
engine would crank but not fire after that, for an hour.
A bad ignition coil has been replaced. At one stage the EGR got blanked off and "it ran well for 3 weeks
after that, then returned". Then a new EGR was fitted and "it went well for a week".
When I checked live data the map was idling at 50kpa but held 34 kpa at 2500 rpm.
I have checked the purge valve and it wasn't leaking but fitted a new one anyway.
Then I theorized that perhaps valve timing could be getting stuck so changed the VVT solenoid - no difference.
Then, since P0401 "EGR flow" keeps returning I removed the new EGR and inspected it and blew out the exhaust gallery and put
it back together and suddenly the vehicle was idling at 34kpa on the map again.
After a test drive it was back at 50 kpa, slowly dropping to 43 kpa as it got warmer.
Most people are suggesting it is an EGR fault, possibly due to an exhaust restriction creating back pressure.
I removed the front O2 sensor and it idles at 34 kpa.
I have been battling to secure an exhaust back pressure gauge locally so this morning I soldered a brake line to the
fitting of my vacuum gauge, the one I bought since joining this forum , and attempted to check back pressure.
All I get is 1/2psi at idle, which stays there at 2500 rpm.
But something that interests me is that from a cold start, on a reasonably cool morning, within 2-3 minutes the fitting
got hot enough to melt the solder off.
My current theory, without knowing what the reading should be, is that either 1/2psi is enough to cause the issue
or perhaps there is something rolling around in the muffler occasionally blocking things up.
I have removed the lower cover of the Cat, which is part of the exhaust, and saw nothing bad looking.

I've just reassembled it and took it for a mild cruise [50kph] to the fuel station and back 4.5km X 2. And the map is idling at 34 kpa again.
Guaranteed if I take it for a 100 kph drive it will be back to 43-50 kpa at idle.

Desmond6004 wrote: P0401 "EGR flow" keeps returning I removed the new EGR and inspected it and blew out the exhaust gallery

EGR Flow problems happen on the Intake Manifold (low pressure) side of the valve. Relatively speaking, the Exhaust side is high pressure. The hot, high pressure exhaust condenses with carbon when it hits the cool, low pressure passages of the intake manifold. Check the intake manifold passages.

All I get is 1/2psi at idle, which stays there at 2500 rpm.

There's no problem, there. I don't worry much about anything under 1 1/2 - 2 pounds. I'm concerned at 3 pounds, though.

Congrats on the move! Be careful about fixing those problem vehicles at a new job - They come to expect it.

Of course this is another one that we don't get in North America, so I can't get SI. How does the PCM determine low EGR flow on this system? Is it like the GM system where it opens the EGR during closed throttle decel?

If that's the case, I'd be interested to see how the EGR monitor goes when the engine is running well to get a baseline. That way, if you happen to catch the car acting up, you'll have a better idea of what you're looking at.

Thanks for the replies.
When I removed the EGR I blew down the intake gallery, to the exhaust side. The other end of the pipe from the EGR to the intake was clean, I couldn't see too well into the chamber but suppose I could get a mirror in there.
It's just strange how removing the o2 sensor got it idling at 34 again, though I did also remove the control parts off the EGR valve and pump the plunger up and down a few times, perhaps freeing it up?
I graphed live data while watching the EGR and noticed that it had a duty cycle and mainly kicked in while actually driving, similar to the purge valve. I think the ECU checks the difference in MAF air flow when it opens the EGR and if there isn't much change it blames the EGR - which may actually already be slightly jammed open[?] at the time.

I took the vehicle home and monitored live data on the way.
In this graph the vehicle has been idling in gear, then in neutral it drops down a bit, then
I put it into gear and take off to 50kph and you can see the duty cycle of the EGR.

Post #5 on this thread is beginning to sound like my problem - a cheap replacement EGR valve sticking occasionally
www.suzuki-forums.com/threads/at-a-loss-p0401-2006-gv.145489/

Desmond6004 wrote: I took the vehicle home and monitored live data on the way.
In this graph the vehicle has been idling in gear, then in neutral it drops down a bit, then
I put it into gear and take off to 50kph and you can see the duty cycle of the EGR.

~25 seconds to ~30mph shouldn't be anywhere near WOT. The fact EGR flow is commanded also suggests part throttle.

But the MAP is up around atmospheric pressure?? I'd go after the MAP.

Also the ECM may use MAP to detect EGR flow so funny MAP readings could be the cause of the P0401.

Desmond6004 wrote: I took the vehicle home and monitored live data on the way.
In this graph the vehicle has been idling in gear, then in neutral it drops down a bit, then
I put it into gear and take off to 50kph and you can see the duty cycle of the EGR.

Wait a second, is this (generally) what the EGR valve looks like?



If so, are there any valve position PIDs? That'll be the trick to catching the valve hanging open or closed.

Just about every vehicle I've seen that uses that style of EGR valve gets checked for flow during a warmed up, closed throttle deceleration. Highway speeds, throttle off and watch the EGR duty cycle blip up. There should be a corresponding change in MAP vacuum. Not enough of a change, or no change, signals a flow problem.

It is a 6 wire EGR - 3 wires for movement, 3 for a potentiometer. But if the EGR sticks open the system doesn't know that, it simply takes longer before the actuator touches the plunger.

I'm going to say this is solved for now. Ever since I removed the electric side of the [1 month old] EGR valve and pumped the spring a few times it has been idling at 34 kpa at idle. This has happened twice now where it's idling at 43-50kpa and opening the EGR and pushing down on the spring brings it back to 34 kpa.
Time for a warranty claim on the EGR.