How to clean the EGR valve?

[enkrypt3d]

I tried searching the forums w/ no luck..... what are the tools required and is it a pain to do? I need to clean it b4 I smog my car again....

I also tried finding it in the service manual but each page is a separate PDF..... so that wont work for me.......

any ideas? Thx

 

[Briank]

I have never heard of anyone cleaning the EGR or having a problem the cleaning helped.

 

[enkrypt3d]

I have never heard of anyone cleaning the EGR or having a problem the cleaning helped.

so should I replace it then? because its causing me to fail smog... (high NOx)

 

[Briank]

The movement of the valve is monitored by the ECU so if its not working you will get a CEL/MIL. Are you sure you have a high NOX reading, that does not happen often. Check your timming.

 

[enkrypt3d]

The movement of the valve is monitored by the ECU so if its not working you will get a CEL/MIL. Are you sure you have a high NOX reading, that does not happen often. Check your timming.

I plan on getting a Scan Gauge so I can monitor fuel trims.... but right now I dont have that option........

the ECU is not throwing any codes yet..... and if the fuel trims are off then what? I'm getting high HC and high NOx ......CO and CO2 are fine..

 

[davidf]

I have seen EGR's go bad due to carbon built up inside over age. But not on an NSX.

 

[enkrypt3d]

I have seen EGR's go bad due to carbon built up inside over age. But not on an NSX.

hmmm is it possible for the EGR to go kind of bad but not bad enough to throw a code?? ugh trying to figure out why i wont pass smog..... :frown:

although im pretty sure the dude didn't turn off TCS while doing the smog test......would that alone cause a failure?

 

[Briank]

Fix the HC problem and the NOX problem will go away. How new are your O2 sensors?

 

[enkrypt3d]

Fix the HC problem and the NOX problem will go away. How new are your O2 sensors?

3 of them are new within the last year....and 1 is brand new.....replaced on friday......

I'm showing no CEL's at all.... I just reset the ECU on friday.... and drove around about 20 miles... is that enough driving to have the ECU relearn the car?

Also, how to fix high HC?

 

[Daedalus]

NOx is moreso created at high combustion temps. EGR reduces combustion temp to reduce NOx, but I wouldn't suspect it either without more troubleshooting. Cats do a fairly good job of reducing all pollutants. In your case I'm a little concerned the high-flow cats might be the problem (or at least a big contributor) because you're bad on all 3 despite keeping the cats at working temp (CO might be a "pass" but it's still too high to be good). In addition, you have residual O2 in the exhaust, which the cat uses to reduce HC in a secondary burn. Often a fail on HC (and CO) shows zero residual O2 as the cat has done all it could but the car is running rich for whatever reason. A high flow cat has less surface area, thus less reduction of HC (and CO and NOx).

Fix the HC problem and the NOX problem will go away.

Is this true? I thought only HC and CO went together. High HC usually works to reduce NOx, since comustion temps are lower if the car's running rich.

 

[enkrypt3d]

thx guys...... all i really care about at this point (b/c I've read a lot of contradicting material about this kind of stuff....) is how to fix this?

 

[Daedalus]

If only it were that easy. There's not a lot to go on here. I believe there is enough O2 in the NOx # to bring HC well into passing territory. If your cats were 100% efficient you would have passed. Stock cats are probably at least 80% efficient...but that still isn't enough to conclude anything. The cats reduce emissions but they're also bandaids that can cover up symptoms of a problem, such as a misfire.

If you at least had a scanner you could determine if the ECU has control of the air/fuel. The HC's being that high makes me question whether the ECU is in closed loop, but I honestly don't know. If the ECU is in closed loop, then look for things beyond its control...(e.g. bad cats, clogged EGR passage, etc). If the ECU is in open loop, then suspect a bad input or something. A scanner will also give you coolant temp.

Just a thought: hope you didn't heat the engine up *too* much. If the coolant temp gets above a certain point the car will run rich to try to cool itself down, in addition to produce more NOx.

 

[enkrypt3d]

If only it were that easy. There's not a lot to go on here. I believe there is enough O2 in the NOx # to bring HC well into passing territory. If your cats were 100% efficient you would have passed. Stock cats are probably at least 80% efficient...but that still isn't enough to conclude anything. The cats reduce emissions but they're also bandaids that can cover up symptoms of a problem, such as a misfire.

If you at least had a scanner you could determine if the ECU has control of the air/fuel. The HC's being that high makes me question whether the ECU is in closed loop, but I honestly don't know. If the ECU is in closed loop, then look for things beyond its control...(e.g. bad cats, clogged EGR passage, etc). If the ECU is in open loop, then suspect a bad input or something. A scanner will also give you coolant temp.

Just a thought: hope you didn't heat the engine up *too* much. If the coolant temp gets above a certain point the car will run rich to try to cool itself down, in addition to produce more NOx.

SIGH so there's really no way to know if my cats are in the right temp then....... everyone says to make sure they are blazing hot, and now u say to make sure its not too hot.... :frown: I plan on buying a Scan Gauge this week... and I'm also taking the car to the dealership to see what they say...$110 for them to just look at it ......arrrrg sigh..... :frown:

 

[lithiumus]

High HC usually works to reduce NOx, since comustion temps are lower if the car's running rich.

From what I understand... High HC indicates unburnt fuel. If there is residual Oxygen but the CO is low then I would guess a misfire or incomplete burn of the HC. If the EGR was flowing too much exhaust gases, it would also make it too rich i.e. the CO would be high.

I just recently pulled off my EGR from my 91 and gave it a good cleaning, but to be honest, it wasn't that dirty given its age. I scrubbed it until it was shiny since I had it out anyway.

Just a thought: hope you didn't heat the engine up *too* much. If the coolant temp gets above a certain point the car will run rich to try to cool itself down, in addition to produce more NOx.

This is a very interesting point. If the car is nice and hot and waiting for an E-test, then it gets on the dyno and is running stable medium revs for an extended period of time, then comes off for the idle test but the engine is now very hot since there really wasn't any moving air to keep the coolant cool... is it possible that the idle would fail esp. if the fan kicks in?

 

[Daedalus]

If the EGR was flowing too much exhaust gases, it would also make it too rich i.e. the CO would be high.

Not without illuminating the MIL. The EGR only works in closed loop mode, and the ECU meters fuel to match whatever O2 is present based on sensor readings. If the ECU can't maintain control in closed loop then it lights the MIL. If the ECU isn't in closed loop then all bets are off (and it's almost certainly running rich).

Keeping the cats hot is good advice because far more failures occur from being too cold. I say it's possible to be too hot, but I don't think it's very likely (for HC). Things cool down fairly quickly once you're off the throttle.

True it's hard to know when the cats are working right (infrared thermometer?) but it shouldn't take much of a drive to get the car to operating temps. The O2s should be kicking in within a minute or 2 since they're heated. The cats take a little more time. My smog guy is about 6 blocks from my house. I drive past him few blocks in low gear, make a u-turn, and pull into his bay. For all I know I might be able to skip the extra few blocks. I keep the revs up to about 3000 in idle until he's ready for me. Often there's no waiting at all. I don't recall the exact #s, but my car is below average on 2 of the 3 (probably HC and CO), and a hair above average on the 3rd (probably NOx).

 

[Onsoku]

I had to use RxP to pass. At AutoZone, ask for part number 214.

http://www.rxp.com/instruct.htm

http://www.amazon.com/RXP-Gas-Kicke..._1?ie=UTF8&s=automotive&qid=1243975256&sr=8-1

 

[enkrypt3d]

........

 

[enkrypt3d]

here are my test results..... it failed under the 15mph test and passed on the 25mph test...... weird!

HC: 92 (max: 85) failed on this
CO: 0.43 (max 0.50) passed on this
NO 702 (max 695) failed on this.....
%CO2: 14.3 @ 15mph and 14.7 @ 25mph
%O2 0.4 @ 15mph and 0.2 @ 25mph

Is the O2 supposed to be this low? Doesn't look right to me.... 0.4 and 0.2% is nothing!

 

[enkrypt3d]

Also, I dont think the smog tech turned off TCS... but I'm not 100% sure... would having TCS on make you fail by itself?

 

[Daedalus]

Is the O2 supposed to be this low? Doesn't look right to me.... 0.4 and 0.2% is nothing!

If the ECU/engine/cats were perfect O2 would be zero. And HC, CO and NOx too. Nothing but CO2 and H2O. .2% is not low. A good-running engine with good cats can show .1% O2 or less. As I already metioned, you also have a lot of O2 tied up in NOx. An efficient cat will separate the O2 from NOx and use it to reduce pollutants.

NOx + CO + HC -> N2 + CO2 + H2O (+O2)

Unbalanced equation of course, coefficients depend on which NOx and which HCs.

I don't think it's possible to do a smog test with the TCS on, but someone correct me if I'm wrong. I don't think the TCS affects air/fuel ratio, just the amount of air the engine gets via the throttle opening.

 

[enkrypt3d]

If the ECU/engine/cats were perfect O2 would be zero. And HC, CO and NOx too. Nothing but CO2 and H2O. .2% is not low. A good-running engine with good cats can show .1% O2 or less. As I already metioned, you also have a lot of O2 tied up in NOx. An efficient cat will separate the O2 from NOx and use it to reduce pollutants.

NOx + CO + HC -> N2 + CO2 + H2O (+O2)

Unbalanced equation of course, coefficients depend on which NOx and which HCs.

I don't think it's possible to do a smog test with the TCS on, but someone correct me if I'm wrong. I don't think the TCS affects air/fuel ratio, just the amount of air the engine gets via the throttle opening.

I guess we would have to know how TCS works (by cutting fuel?) if so it would make the car run really lean...

 

[Daedalus]

I guess we would have to know how TCS works (by cutting fuel?) if so it would make the car run really lean...

I know for certain it cuts air by closing the throttle plate. I'm just not sure if it does anything else with the mixture. If anything they would make the car run rich rather than lean. Lean is dangerous.

 

[enkrypt3d]

I know for certain it cuts air by closing the throttle plate. I'm just not sure if it does anything else with the mixture. If anything they would make the car run rich rather than lean. Lean is dangerous.

how is lean dangerous?

its obviously running lean since the NOx is high based on what you guys are saying...... right?

 

[Daedalus]

how is lean dangerous?

A little lean is OK. Too lean can cause misfires or temp/pressure spikes and detonation. The ECU doesn't know exactly in advance where "too lean" is. Again, I don't think the TCS changes the mix. But in general ECUs tend to run on the rich side when not in closed loop because it's safer.

its obviously running lean since the NOx is high based on what you guys are saying...... right?

I didn't come to that conclusion. NOx is high, but so are HC and CO.

 

[nsxotic911]

Cool - did u run a whole tank first then fill up or just go 30 min after u put it in? (just ordered some thx!)

Auto-Rx is good stuff. May not fix your problem, but it may help enough to get passed smog. It did with my Civic, until it blew up (sort of..)