Emission testing question

[INF3RN0666]

Hey

I have a 2000 impala 3.8L with 350K kilometers. The problem is, it has a random misfire that mechanics can't seem to diagnose, and many parts have been replaced with no success. The issue is that I have to get it tested for emissions. Do you think there's a chance of it passing if it misfires at idle? I'm thinking NO, but I'm hoping I'm wrong.

[Sute]

Propabaly it will not pass, coz misfire will lead to a relative high temperature inside the cylinder, and there will be more NO generated, even its at idle.

[2.2 Straight six]

yeah, if it's missing then you'll get more raw fuel in the exhaust, more NOx and stuff.

[maxwedge]

In NYS it will pass if no CEL or pending codes, do you have a cel?

[2.2 Straight six]

i'm guessing he's in canada because he mention mileage (or kilometerage) in km.

[INF3RN0666]

lol yup you got it. i'm in canada. I had a feeling you guys were gonna say that. The problem is that it's missfiring and every mechanic says something else or can't speculate on the problem. My most reliable mechanic tested a few things and said it was the rockers. Problem is, he doesn't wanna take the engine apart because it's time consuming. he recommended I just swap the engine. So I'm rethinking the statement: "my most reliable mechanic".

Just a brief history:
1. car misfires at idle.
2. replaced wires and plugs --> no change
3. tested codes --> they were: random misfire code, EGR, O2 sensor, MAF
4. replace EGR, O2, and MAF --> it made the codes go away, but no luck with the missfire
5. the mechanic said he tested the coils and injectors with no luck.

For me, I have a feeling it might be a vacuum leak or a power problem.
Would a weak battery or alternator cause this? (battery is always 12 V, even after a long drive on the highway)

[UncleBob]

I worry about a mechanic that can't diagnose a hard misfire. Thats one of the easier things to figure out, out of the spectrum of runnability problems

I don't know the specifics of the emission laws in canada, so i couldn't give advice on that, but if they have any kind of waiver availible, you would have been best off failing the emissions test first and then attempting to get it fixed. But like I said, I don't know the regs there

I know its not very helpful, but I would suggest a better mechanic. A consistant hard misfire shouldn't require much guessing IMO

[Rawtorque]

1. The timing chain may be worn, causing the valve timing to do weird things.

2. I don't know *how* he tested the injectors properly with an active misfire. Maybe you should get them cleaned.