Now I gotta change the CAt. How much should I pay for a new one?
Are you sure you have to change the cat?? Or is that what they told you at the shop? Post your results. Alot of times bad emissions are miss interpreted even by class A techs. 75% of car that fail e-test do so because of a fualty O2 sensor. You can test the O2 sensor yourself with a DMM (digtal multi meter) by disconecting the wire and puting + lead on O2 and - to any ground. Then with the car running watch the voltage …should be around .5v then pull the vacuum line to the fuel preasure reg of and block the hose of with your finger. This sould creat a rich mixture and the voltage should go up to around .9 and at a fairly rapid pace. If it does not reach .8-.9 V or gets there really slow then O2 is faulty.
You can test for a lean reading by simply plling any vacuum line(not fuel reg) and the car should go lean and the volts will drop below .3 if not it is faulty.
It is easier and cheaper to do this test and replace the O2 if needed then to replace the cat and find out you still fail.
Just a heads up. But post your results.
Chris
I failed twice as well, now I got some sea foam from car quest and ran it through my engine and Im positive Im gonna pass.
hc ppm = 9(30 limit)---------------10(idling) PASS
CO====0.02(.30limit)------------0.02idle PASS
NO ppm=875(first test)@25mph FAILED 770 LIMIT
1000(second test)@25mph FAILED retest 770 LIMIT
I just tried it the second time to see if it would pass but I didnt tune it up or anything. My pops a cert mechanic told me that I needed to tune it and if it fails I might need a new CAT. See I could have passed it easily but my dad does not have the time to fucking tune his sons car.
I stongly recommend just changing the cat. Reason being …
If you had a bad o2 sensor - on the e-test (in my experience - most of the time) it would show HC and CO reading, to be very close the failed limits.
Also by doing a tune up, I also have experienced an elevated HC reading - and sometime failing etest.
As you can see from your e-test your HC & CO limits are very low. But your NOx is slightly high. This is why I stongly recommend just changing the cat.
Just remember that - once you replace your old cat with a new one … you must drive it for about 20 min on the highway (to wake it up, as new cat. take a few miles to start to store oxygen in the cat) before your next etest.
NOx is caused by heat ( cumbustion is too hot). Heat is created by a lean mixture, while the cat could be your problem in this case I would recomend a tune up. Reduce your timing slightly and run some injector cleaner through it as well as run high octane and you should be good. I am not disregaurding the cat but it is cheaper to do a tune up yourself (if capable) then to get a new cat. Your car could prob use a tune up anyway and will help with fuel econemy and power. Kill 2 birds with one stone!
Also to touch on Chris’ point, the extra combustion heat could be caused by a sticky egr valve, since part of what the egr system does is reduce combustion temps. All part and parcel of the tune-up he mentioned you should get.
If the EGR valve was sticking or not functioning properly … the NOx in my experience should be approx. 2000 ppm (post-cat)or after cat)) … This vehicle should produce approx. 3000 ppm (pre-cat.) or before cat)) -depending on how carboned up the motor, and how bad the radiator is.
A good rule of thumb is that the EGR reduces the NOx by 50% (before cat) and the Cat reduces the NOx by an additional 25% … so you have a total of 75% reduction of NOx - in the system (compariing before and after cat reading)
Any good garage should do a comparion test before and after cat to see the real picture of all 5 gases - no the 3 gases you see on the sheet. That what I do
I you want to cheat … at a ¼ tank - use 3 liter of alcool (methal hydrayte) … just remember after the etest - fill the tank ASAP - or you can cause prolong damage
I have see it done - I dont recommend it, so do as you see fit