Dr_Shakalu

Hi everyone. Well, my car failed because of high NOX. I'm in the process of changing the egr valve and egr valve solenoid. However, since I'll be changing the 2 parts, I might as well clean the egr passages. What is the best way to clean the passages and how hard of a job is it. Thanks in advance, Ed.

bogus

Blast some throttle body cleaner in there... won't effect the results, tho.

Dr_Shakalu

Why will cleaning the passages not effect the results? I may be wrong, but wouldn't passages clogged by carbon build up affect the vacuum that flows through it? Also, what about using a small, thin brush and some cleaning fluid?

65Z01

What year Vette? Assume the fog nazzies use a dyno sniffer?

EGR is only called for after steady speed for a few minutes with coolant temp >175deg F, at least that's true for my '88.

I think high NOX is caused by high chamber temps and lean burn.

tbirdsps

As 65Z01 said when did it fail NOX? If it was at or below 2,000 rpm it's not the EGR causing it. The EGR only opens above 2000 rpm thus why most states require a 2500 rpm test. If NOX is high at idle the engine is lean.

cv67

You can remove the intake heat shield and the large plugs, blow them all out real good do that as a last resort to you may not need to

Dr_Shakalu

I live in California so if you look at the code in the bins egr begins at 1200 rpm.
In Cali they run it at 15mph and 25mph loaded on a dyno, so rpms are usually 1500 to 1800. These are the numbers from the smog test. All the other numbers look great. Just the NOX too high.
NOX at 15mph. CO2=0.0 @ 15 & 25 mph, HC=1 @15 & 25 mph and CO=0.0 @ 15 & 25 mph. This is the results for the NOX which I failed. NOX = 612 @ 15mph FAIL and NOX=705 @ 25 mph barely pass. No codes.

mtwoolford

OMG

I just went through NOX hell. It was on a 96, not my 96 corvette, but my 96 chevy cavalier; however the lesson learned is generic

long story short...and believe me it was a very long story...the issue finally boiled down to carbon in the exhaust passage and small...as in tiny...carbon chunks lodging between the EGR valve pintle disc and seat....since the little chunks would come and go the NOX readings (multiple smog tests) were all over the map. Eventually cleaned the EGR exhaust passages with brake cleaner to soften / loosen the carbon and then blew them out with compressed air; NOX dropped from 1100 ppm to 49 ppm.

consider buying an LT4...no EGR !!!

good luck

cv67

Wow what a pain tracking that down?
Smog laws are bs out here.

Its not the cars theres just too many flippin people here
Get the ones out that arent supposed to be here the air would clean up immediately and cost of housing would drop. but NOOOO cant have that.

Sleazy Rider

wydopnthrtl

If you have the parts off by all means do what you can to clean the passages. Brake cleaner and a flexible bottle brush works well.

Also, there are two small things that can help get a cleaner burn. 1. add just a little acetone to the fuel. (1oz per 10gal) It'll better atomize and get a more complete combustion. 2. Take a small file and skin a little fresh metal on the ground strap and center electrode.

(blocked egr passages were always a problem on the GM3.1L engines)

cv67

Also on 80s TBI engines.
Had an 87 Van that the EGR passage was completely coked up solid that one had me stumped for awhile.

bogus

I wish you had been specific to the car... you are right that some cars are more touchy, but the LT1 isn't one of them.

Honda has a longstanding issue with their engines... they have this little injection port for the EGR back into the combustion chamber, in the intake manifold. These ports get clogged and that's about that... engine light lights and you have an EGR code. The only real fix is to pull the intake and hot tank it.

john3322

i think you should contact any expert of this field