EGR problem

[ZMARKUS]

Got a p0400 code and figured maybe the ports are clogged but first I'll clean the EGR valve. It was a little dirty but that didn't remedy the problem. Had my mechanic check to see if any tubes had become brittle that may also cause CEL. He came back with saying there was some carbon buildup, but also the EGR solenoid needs replacing because the EGR valve is staying open. He says he's getting a vacuum on some lines when he shouldn't. This indicates to him the EGR valve is staying open and because of location of EGR solenoid, I would be looking at $650 to replace solenoid and clean EGR ports. He says the car would be dying at idle if not for the carbon buildup. I currently have no driveability problems. I just had a EGR cleaning service this time last year. Could it be so coked up now that it's the only thing keeping my car from stalling? Althouh, this guy is a nissan/infiniti specialist and good, at that price it seems it wouldn't hurt for me to get another EGR service and see what happens. It could be very well be the solenoid but I kinda believe in starting out small. What if it's just the carbon that's an issue. What you Infiniti folks think, is this EGR solenoid a common failure with the Q. Should I just get a EGR cleaning?

[maxnix]

It's not apparent from even reading the manual, but if you don't pull the plenum and clean the EGR tube within (and once you see them, the plenum and lower runners), it really doesn't matter if everything upstream is purty as new.

[ZMARKUS]

It's not apparent from even reading the manual, but if you don't pull the plenum and clean the EGR tube within (and once you see them, the plenum and lower runners), it really doesn't matter if everything upstream is purty as new.

Although this technician is a skilled one and specializes in Nissan/infiniti, could the solenoid factor possibly not be. I ask this in the spirit of focusing using on the smallest possibilities first, hopeful it's not the issue and a sprinkle of denial.

[Q45tech]

The solenoid drives the air valve which cuts the vacuum signal at idle and cruise anytime the coolant is not warmed enough from an ecu signal.

The failsafe position would be open so no vacuum signal is applied and thus no EGR when solenoid or its signal fail. EGR code and emissions failure [high NoX]..................1-2 mpg lose at steady cruise without egr.

[ZMARKUS]

The solenoid drives the air valve which cuts the vacuum signal at idle and cruise anytime the coolant is not warmed enough from an ecu signal.

The failsafe position would be open so no vacuum signal is applied and thus no EGR when solenoid or its signal fail. EGR code and emissions failure [high NoX]..................1-2 mpg lose at steady cruise without egr.

So do you feel there is accuracy regarding my mechanics notion that my egr valve is remaining open by a none working solenoid and the only thing keeping my car from dying at idle is the carbon buildup in the egr ports. I mean, I had a egr service done last year this time. Could there be another reason why the mechanic is getting vacuum when he says there shouldn't be. I'd like to think a simple carbon cleaning would remedy this.

[Q45tech]

If there is a lower than atmospheric pressure [from a leaky solenoid valve] to suck the diaphram UP or a leak in the diaphram the EGR gases can flow into plenum.

Common for EGR tube from exhaust manifold to gunk up [gradient clogging =none > total clog] . Function of highway miles vs city miles [cruise vs acceleration].

There are fail safes to make sure there is adequate exhaust pressure to simulate cruise rpm plus the ecu doesn't energize the solenoid until 1500 rpms or greater STEADY.

The point is any acceleration cuts the EGR gases unless solenoid internally.

All of the items can be easily and quickly tested.

Solenoid valve failure is very common on Toyota but not Nissan.

We use a mini roto rooter driven from a hand drill to clean the main metal tube from EGR valve to exhaust maniforld.

Dealers replace the tube as age may weaken it and cause cracking.

Owning heavy V8 imports requires lots of annual money for tire, brake and parts replacement on top of mainteance costs.

3 hours + equivalent parts is not uncommon every 6 months.

I spend around $2500 per year [prorated and average but you can see some $6,000 years along the way if things wear out in unison], but mine in 9 years older but after 10 years they are all the same.

The point is my 10th and 11th year were most expensive of all!

[Q451990]

So do you feel there is accuracy regarding my mechanics notion that my egr valve is remaining open by a none working solenoid and the only thing keeping my car from dying at idle is the carbon buildup in the egr ports.

The EGR valve will fail closed unless there's an obstruction there - like carbon buildup - although I've never heard of it.

I noticed you're in Charlotte... I don't have any experience with these guys, but they look like they have "T3 North" potential. It might be worth getting their opinion on your situation. http://www.nisstech.com/

Heath

[ZMARKUS]

Thanks, I

The EGR valve will fail closed unless there's an obstruction there - like carbon buildup - although I've never heard of it.

I noticed you're in Charlotte... I don't have any experience with these guys, but they look like they have "T3 North" potential. It might be worth getting their opinion on your situation. http://www.nisstech.com/

Heath

Thanks, I'll check it out.

[ZMARKUS]

If there is a lower than atmospheric pressure [from a leaky solenoid valve] to suck the diaphram UP or a leak in the diaphram the EGR gases can flow into plenum.

Common for EGR tube from exhaust manifold to gunk up [gradient clogging =none > total clog] . Function of highway miles vs city miles [cruise vs acceleration].

There are fail safes to make sure there is adequate exhaust pressure to simulate cruise rpm plus the ecu doesn't energize the solenoid until 1500 rpms or greater STEADY.

The point is any acceleration cuts the EGR gases unless solenoid internally.

All of the items can be easily and quickly tested.

Solenoid valve failure is very common on Toyota but not Nissan.

We use a mini roto rooter driven from a hand drill to clean the main metal tube from EGR valve to exhaust maniforld.

Dealers replace the tube as age may weaken it and cause cracking.

Owning heavy V8 imports requires lots of annual money for tire, brake and parts replacement on top of mainteance costs.

3 hours + equivalent parts is not uncommon every 6 months.

I spend around $2500 per year [prorated and average but you can see some $6,000 years along the way if things wear out in unison], but mine in 9 years older but after 10 years they are all the same.

The point is my 10th and 11th year were most expensive of all!

Thanks for the info and yes the big boy V8 require sufficent funds to be maintained but it's all good. All repairs on my Q have been in general though. Now, I don't mean to insult this forum by mentioning Lincolns, but the Q pales in repairs compared to my Lincoln Ls. I've had everything but the coffee maker fixed on that thang. It was my first and probably last american car. It's beautiful but sh*t breaks unreasonably with that car. I still love it though.

[ZMARKUS]

So do you feel there is accuracy regarding my mechanics notion that my egr valve is remaining open by a none working solenoid and the only thing keeping my car from dying at idle is the carbon buildup in the egr ports.

The EGR valve will fail closed unless there's an obstruction there - like carbon buildup - although I've never heard of it.

I noticed you're in Charlotte... I don't have any experience with these guys, but they look like they have "T3 North" potential. It might be worth getting their opinion on your situation. http://www.nisstech.com/

Heath

Well these Nisstech guys took care of the problem. The egr ports were clogged and solenoid was non functional. They manually cleaned the ports by removing intake manifold and replaced the solenoid. Took it to inspection two days later and passed with flying colors. The owner is named Jeff, super honest nice guy. They're now part of my Q45 fix it arsenal.