smartypants

Hi All :

I took my 99 TL to get it's emission check in order to renew my plates, and much to my surprise, it failed ! Apparently the NO (nitrous oxide) levels are double to allowable limit. This is really annoying because the sticker has expired and I'm running around on expired tags. The service manager mentioned the problem is probably a cooling issue around the combustion chamber (huh ?) or a faulty EGR valve. For the record, the temperature gage has never moved from just under the halfway position since new.

I've had a running battle with a 1491 code (insufficient EGR lift) for over six years. You can look up my previous posts if you're interested. I've done the full port clean (it was blocked), taken to EGR valve off and cleaned/lubricated it with no results. I had planned to replace the valve when I was on trip to the US in December, the stealership here wants $200 just for the part.

To pass the previous emission tests, I've simply reset the CEL (they won't even allow the test if you have a CEL on) and the car has always passed with flying colors.

Does anyone have any experience with this ? If the EGR valve is completely dead, would the NO levels skyrocket like this ? I'm completely screwed until I resolve this issue as the car will have to be parked for the duration. Also, I have to pay for each test attempt and so just blindly changing parts and hoping for the best may not be the way to resolve this.

Big thanks the ALL who reply !!

01tl4tl

what happened this time--the reset didnt work? or it failed on the actual test readout?

No one will smog ck a car with CEL- that means something is wrong~

the oil can hold large amounts of Nox if its been a long time since change,
but double the limit seems like worse than that~

test the egr valve itself- see if it opens and closes with rpm change
closed at idle- open at other times except full throttle

test out the cooling system too- I dont care about the guage unless its overheating reading- it can LIE about whats happening inside

remove rad cap--level is ok? color? no traces of oil transfer?
let engine warm up, observe coolant flow thru rad opening with rpm changes
fan operates as needed?

remove spark plugs- inspect each, and run a compression test on each cylinder
If one cyl. is lower, add a few drops engine oil thru plug hole and retest
If its rings that will raise the reading

If valves- its blowing oil past them and exhaust fumes into the oil and exhaust pipes- will affect smog reading

6 year ongoing prob--when did you last clean the erg ports?

smartypants

Two months ago. See previous posts on that very topic.


One thing I should have remembered, I run regular gas and I should have tanked up with premium for this test. Again, it's always passed with regular fuel.

fsttyms1

So did you actually replace the EGR or not? The way i read it is no. Odds are the egr is probably shot and in need of replacement, Are you sure the ports are all clean?

smartypants

You are correct, no replacement. As for port cleaning, I have carb cleaned and "coat hangered" the port to death.

Always nice to hear from our "Brain Trust", fsttyms1

smartypants.

01tl4tl

who has the test procedure for the egr valve?

one of our acura dealer master techs?
please post

fsttyms1

^ like this?

smartypants

Thanks fsttyms1.

While I do have the tools to do this procedure, given the NOx is higher than spec, I'm thinking it's not an electrical issue but a mechanical issue with the valve itself.

Correct me if I'm wrong but, the value works on pressure coming in from the exhaust, which causes the value to open more as the engine RPM's increases, supplying a varying flow of gas to the intake manifold. The electrical portion of the valve senses the movement and "reports" the movement (or lack of) to the PCM.

Now, I may have this backwards. It could be that the PCM sends a signal to the EGR valve to open or close in lock-step with the engine RPM. However, in either case the valve does not seem to be opening and providing gas to the intake and causing the higher NOx levels.

My current thinking is to change the EGR and hope for the best unless someone here can provide other ideas.

Thanks again.

smartypants

01tl4tl

did you say you took the egr valve off and cleaned-lubed it already?

those test should tell you if the valve is working correctly

I dont buy parts until basic test like compression are done
a number of things can cause your ongoing problem
DIAGNOSE step by step unless you like throwing money at a problem until something fixes it
What are you--training to be a Service Writer??

Are the engine pressures on spec, thats first- compression ck tells many things and each spark plugs condition tells even more

ok does the egr valve test good, ok does the....

or drive it across the line and let kris have at it~

01tl4tl

ck in the REGIONS link at top of page, its broken down by areas for ziner meets/gatherings
see who is on the past gathering list and ask for help
Surely a ziner near you is, or knows, a smog tech to help troubleshoot with you

smartypants

I'd love to let Kris lose on my car !!!!!

Changing out the EGR valve is so simple as opposed to performing all the electrical tests. If the valve is found not to be the cause, then I'll do all that detailed work. Unforunately the part is relatively expensive ($200) and it takes days to get the CEL to come on to know if it's fixed.

01tl4tl

make the drive to a parts store here with better prices~

seafoam oil and change it before next test
seafoam manifold and gas to clean residue anywhere along the path

smog station usually offer for ~25$ a `pre test` to see if the numbers are fixed

use that Meets section to borrow an egr off another TL for testing part

smartypants

The on-line dealer price is $150, but the exact same unit is available through a number of on-line parts places for $92, however I need to be able to walk in and pick one up at a "store" in the Buffalo area. Autozone has an (Wells) aftermarket unit for $72 which might work. Although, I would prefer OE but I can't seem to find a national parts distributer in the Buffalo area that carries the OE version.

I'm also going to put ultra high test gas in the tank but, I'm not sure this will help as it will increase the combustion temperature which creates more NOx.

Thanks for helping out 01tl4tl

Anyone else have anything to add ?

01tl4tl

if you dont like seafoam - use other brand like redline SI-1 FI cleaner (my fave for gas tank) or lucas- at MAX dose to remove the buildup in the engine-
carbon and combustion byproduct: its real - its there- deal with it~
may take 2 treatments thru the tank with those products
Use full bottle to half tank

If its got excess Nox it probably loading up the cycls too--had a look at the plugs recently? they reveal a great deal of info- there are plug reading charts online to tell you what color and buildup mean

retest?--I said PRE test to know if its been fixed without running it thru the full system of reporting to the govt etc,,,they may call it different in your country

Do what you want--I gave my advice the rest is up to you,, or others smarter than I,,, on this issue

cleaning out the engine intake system/remove carbon, is a standard thing for techs to do in mystery problem diagnosis--
got to have a baseline of clean to figure out whats happening sometimes!

Shops have a machine that runs seafoam or similar cleaner mixed with gas, hooked into the fuel lines--
we add cleaner to gas tank,, and thru manifold for faster result but same idea

I operated the fancy `fuel injection system cleaning machine` in a shop as a tech and service writer- great!! easiest 100$ sale for 10 minutes tech time connecting the hoses- let the car run by itself for half an hour off a can of gas and seafoam --then make the customer do the after drive,,too bad it was cooled by then and not as effective at blowing out the crud

my honda bike actually requires frequent `decarbonizing` with a spray cleaner used same as seafoam--sold at honda bike dealer for 10-12$ a can
The book says that the buildup MAY cause the valves to contact piston due to increased piston height, with the carbon layers

Our car engine is the same- has to have actual cutouts/detents in the piston top to clear the exhaust valves when they are full open
Misadjusted valves can contribute to the interferance engine problem
tight exhaust valve is extending farther than designed--danger!!

fill those cutouts with crud and the exhaust valves will make contact,,result is bent valve with bad edge seal.. or damaged valve and seat,,like breaking a timing belt

dukie564

High NOx emissions are caused by excessive heat due to high combustion chamber temperatures.

Causes of high combustion temp:
1) The cooling system. This system needs to be in proper working order or the engine can run hot, which can elevate NOx emissions.

2) Incorrect timing or spark advance.

3) Carbon deposits in the combustion chamber. Run a compression test.

4) Incorrect spark plug heat range. Always verify that the plugs are the right application and heat range.
5) Incorrect vacuum to the EGR valve. First check codes in the engine control module (ECM). In most Hondas, if it has an EGR problem it will set a code.


I've also seen this problem arise from an improper signal from the O2 sensor.


I would run the tests first, then replace the O2 sensor. The LAST thing you should do is replace the EGR valve (definitely the most expensive part to fix), unless the tests tell you otherwise.

01tl4tl

SeaFOAM seaFOAM seaFOAM

see #3 above for why-carbon!!!!!

01tl4tl

in the states- parts stores loan tools including comp tester- maybe your parts store will too- with a refundable deposit?

higher compression due to carbon layering on piston is a really really bad thing

how old are the spark plugs? combo job labor if cking compression

01tl4tl

have you ckd the coolant abilty? is it less than 5 years old?
pressure test cooling system--same tool loaner program

is the res at max cold and rad full to the top when ckd dead cold?

there have been a number of radiator cap failures recently- that makes the system push less flow = less cooling in the cylinder block but fools the rad temp sensor for guage on dash

from OP first post: The service manager mentioned the problem is probably a cooling issue around the combustion chamber (huh ?)

that would go back to rad cap or water pump-
take the rad cap to parts store - they should have a pressure testing tool-- same one as for rad

cheap first step is replacing it--and get seafoam while you are there- dont care if you are a fan- need to get rid of a problem right????--then use right tool for the job

smartypants

Thanks to everyone for responding and helping me out with this situation.

I've gone over the workshop manual and listened to several folks, both on-line and off-line. Given that I'm not a tech (nor do I play one on TV) my approach is to wade through the various recommended actions and look for the common bits of information and advice.

Firstly, the only component that effects/reduces NOx levels is the EGR system. It's exclusively designed to reduce this gas buy recirculating exhaust through the upper part of the engine, reducing the combustion temperature and as a result, reducing the NOx level.

The way to test the system is go through the testing procedure in the manual and see if the system is working. It seems to do this by "jumping out" the PCM signals to see if the engine responds to the valve being improperly set (rough or stalling engine). This demonstrates the system is sending gas around and that the valve is opening and closing (albeit improperly for testing purposes).

So, I'm going to be performing the test this afternoon and see if the valve is working and if not, I'll be changing it out.

I'm writing this so that if another member goes through this, there will be a thread to follow and hopefully add some value.

smartypants.

01tl4tl

may be the only COMPONENT that effects,, but not the only thing~

smartypants

This afternoon I started to perform the voltage checks as per the shop manual. None of the voltages seem to match the manual. Battery voltage (12V) is 7.5V, 5V is 1.5V so it looks like all the voltages are low.

The manual suggests I continuity check back to the PCM. How does one access the PCM ? I believe it's under or near the radio.

Now, if the testing continues like this, it may be the PCM is bad. Is this possible ? The +5V looks like it come from the common sensor voltage. So if its low (1.5V), would it not affect the other sensors ?

Anyone have lots of experience with the PCM ?

smartypants

01tl4tl

did you ck the voltage of the battery? low volts will screw up all the sensors

smartypants

Bang on 12V.

01tl4tl

thats low iirc

smartypants

Anyone out there had any experience performing the electrical tests on the EGR system ?

Here's what I found when I perform the test detail in the manual.

1) The battery voltage at pin 4 and 6 is 7.5V (should be 12V) but when I rev the engine up, it blips up to 12V and back down again to 7.5V.

2) The +5V between pin 2 and 3 is not there. However there is +5V at pin 1.

3) When I applied battery voltage to pin 4 and 6, the engine did not respond but, I did here a "click" indicating the valve is opening and/or closing.

Could the manual be wrong with regard to the test results ?

Any techs had "real" experience with this ?

smartypants

smartypants

So, today some good news.

I replaced the EGR valve and had the car retested. This time it passed with flying colors. Now, I'm not going to call this closed until I'm code free for at least week or two.

Funny thing, when I plugged in the new valve, the scanner immediately detected a pending code. I think it was due to the new valve sensor being set differently from the old one and totally confusing the PCM. I also did a hard reset and there are no current or pending error codes.

I'll be writing up the problem and solution to this situation in a final message if all the issues remain resolved. I hope it helps others in the future.

Time will tell.

smartypants

smartypants

Hi All :

After 7 years of the CEL always on, I have now gone for 2 weeks with no codes and am now declaring the problem solved. I'm writing this final response for those who encounter this problem in the future in hopes that this info will help others in a similar situation. When I first experienced the problem, I searched the site and did not find much detailed information regarding the EGR and my hope is that this reply will help solve that gap.

The EGR is pretty much a closed system and is used to circulate cooler exhaust gases around the combustion chamber to reduce NOX gas for smog reduction purposes. The components of the EGR system are; the EGR valve, EGR port(s)and the PCM. Here's how it works; the EGR valve contains two circuits, a high voltage (+12V battery voltage) and low voltage (+5 common sensor voltage). The low voltage powers a sensor which feeds back to the PCM an exhaust gas value. This value causes the PCM to vary the high voltage to the valve, causing it to open and close, allowing more or less gas into the cylinder head. In this manner the PCM "learns" what setting at specific RPM yields the most NOX reduction. This information is important if you need to ultimately replace the valve.

The symptoms of an EGR failure is CEL code PO1491 ("Insufficient EGR port lift") as described in the "EGR Port Clogging" service bulletin #00-004 dated Dec 17, 2001. There are no other obvious symptoms with this problem other than the potential for failing an emissions test due to the system simply not working. For example, with a bad valve my NOX was 1427ppm and with a new valve it dropped to 27ppm. (I do have to add that I did not do a hard reset of the PCM for the failed test which may have negatively affected the readings. I had use the hard reset as a tactic for years to pass the E Test)

Two issues will cause the code to appear, a blocked EGR port(s) or a bad EGR valve. Since cleaning the port should be part of the regular TL maintenance (see the service bulletin for complete instructions), always start there first. Ensure the port is fully cleared by using liberal amounts of carb cleaner and a coat hanger or some other flexible "probe" to make sure it's completely open. Remove the EGR valve and clean the bottom of the valve and the port it bolts to, again using a coat hanger to make sure it's clear. This step is not included in the service bulletin and really should have been. Removing the EGR valve is very very simple, two nuts and a connector.

Once you have completed the port cleaning, reset the CEL and see if the code comes back. This may take upwards of a week to reappear so don't expect a code when first starting up the car, unless of course you did not reset the previous error. If the code comes back, then the EGR valve is bad and needs to be replaced. One important point for those who have code readers. Immediately when first starting the car, you might see a pending code because the PCM has "learned" it's settings from a bad valve and now a new set of (now accurate) values is being reported which are completely different from the stored values. Hard reseting (removing power) to the PCM will correct this.

The technical manual details out an electrical test (it's also included in this thread) to confirm if the valve is good or not. I attempted to perform this test and could not get the results indicated in the manual. For example, +5 sensor voltage was supposed to be seen between pin 2 & 3. I saw +5 on pin 1. My recommendation is to ignore this test as it seems to be documented incorrectly. (yes, my ego is big enough to say the manual is wrong)

The OEM EGR valve is $150 from the dealer, but many parts distributors have the identical part for $95. The "real" part will have a pale blue round cap on the very top of the unit. Autozone has a (Chinese) replacement part for $80 and given the low risk (the engine runs just fine with a bad valve) and the simplicity of replacing the part, the cheaper part has little downside risk.

Good luck to all !

smartypants.

01tl4tl

7 years of living with a CEL, faking your way thru smog test, emitting high nox--
and the fix was only 80 bucks

sounds about right if it were a mechanic owned car~