93 Jeep Wrangler - 57K miles - fails CA smog

About 2000. It really is a third car.

Jim.

The Merg wrote:

I only went to the test-only station. The tech there said the other repair shop did not repair anything that would fix this except a new cat will normally get this to pass.

I've applied for the CA assitance for test-only vehicles. So I have to wait to take it in.

I've been reading online and it very well could be my EGR valve is stuck or broken.

Jim.

The Merg wrote:

If they really did replace your catalytic converter last time, then the EGR, if you have one in that vehicle, is indeed a likely suspect.

Earle

I only went to the test-only station. The tech there said the other repair shop did not repair anything that would fix this except a new cat will normally get this to pass.

I've applied for the CA assitance for test-only vehicles. So I have to wait to take it in.

I've been reading online and it very well could be my EGR valve is stuck or broken.

Jim.

The Merg wrote:

Just so you know, the warranty on a replacement catalytic converter is 5 years, 50,000 miles. It used to be mandated by Federal Law. Don't know if it still is, but maybe you can use that if you need it.

Spdloader

I only went to the test-only station. The tech there said the other repair shop did not repair anything that would fix this except a new cat will normally get this to pass.

I've applied for the CA assitance for test-only vehicles. So I have to wait to take it in.

I've been reading online and it very well could be my EGR valve is stuck or broken.

Jim.

The Merg wrote:

Jim,

Excess NOx is a sign of too much heat during combustion process (well, for emissions purposes anyway). I don't know how picky your local test only shop is, but retarding your timing a few degrees is the easiest and fastest way to get around that problem. It's worked for me for years in other states running the same smog test. Hm, for that matter, make sure your timing is set properly to begin with.

I agree with Earle, a failing EGR system will fail your NOx too. On a

14 year old vehicle with as little mileage as you have on it, I'd carefully check the passages for obstruction.

Assuming the cat's numbers were the same before and after replacment, it's doing its job to the best of its ability, so take that out of the equation.

Jon

Earle Hort> If they really did replace your catalytic converter last time, then the E= GR,

Aw shucks, I don't even know if your engine/year allows for timing adjustment. If not, well then one less option.

J> Jim,

High NO usually indicates a problem with the EGR valve, plugged EGR passages or a leak in the EGR vacuum circuit. I had the same problem with another vehicle last year, and a replacement EGR valve solved the problem.

Warning: don't buy an aftermarket EGR valve --they're junk. Go with an OEM part regardless of cost. I learned this lesson the hard way.

Thanks for the responses. Yeh, it seemed like the EGR. So I started checking for replacement EGRs for my Jeep. Cannot find any at any site. I have a service manual and so I looked up EGR. Jeep removed the EGR from the wranglers in 1990. So my 1993 does not have one. It might be regulated by the computer. Maybe the hose is plugged or something.

Jim.

Outatime wrote:

My Haynes manual mentions an "EGR Solenoid" for later models. It's not a very good manual because it tries to cover too many years. Check the Vehicle Emissions Control Information label under the hood, if it is still there. That is really the only reliable indicator, for what emissions control equipment you actually have. They come right off with steam cleaning.

Earle

Give up on the EGR already. It doesn't have EGR.

Anything that increases combustion temp can cause high NOx. Carbon buildup, wrong spark plugs, slow O2...

To get the right stuff out of the cat, you need the right stuff going in. Unlike the old days when leaner was better, to control NOx, the cat needs some CO to get the job done. A large exhaust leak could contribute to high NOx numbers.

I thought that...

I would be thinking carbon buildup in a vehicle with so few miles on it. A good high rpm highway run or a good run in 4 low can sometimes blow the carbon out or a de-carboning job 'will' clean the carbon out for sure. They have products your mechanic might be able to use or you can slowly let the engine ingest a pint of water while you keep the revs up enough to prevent a stall. One of my older vehicles flunked emissions and I just paid the guy to do an upper cylinder clean. It then passed.

The water shock will clean the carbon out. I use ATF instead of water for this just because I was taught that way and know it cleans the combustion chamber like new. When I worked in garages, they use to do the ATF cleanout on city driven vehicles to get rid of run on and pinging under load. I always do this before a head gasket job so I have everything clean for inspection. It makes a massive cloud of smoke though.

I have been told you can use a vacuum line to suck the water into the intake for this job. Something like the PCV line would do I believe.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail > Thanks for the responses.

I agree; very high combustion chamber temps will be the problem.

If not equipped with an EGR "system", other reasons for high NOx are:

• Incorrect timing (too far advanced)

• Excessive combustion chamber deposits (check with compression guage)

• Lean fuel mixture, which can be caused by many things including O2 sensor problems, intake leak, MAF problem, etc.

• Hot spark plugs which can ignite the fuel mixture prematurely

• Badly functioning cooling system (would have to be VERY badly overheating to cause this)

I would start with the simple stuff; verify timing and advance mechanism, do a compression check on all cylinders (water injestion can often knock out what's in there) and verify the cooling system temp with a digital thermometer and DVOM to verify fan engagement temps. Change the spark plugs with known proper type. If that all checks out, it's time to find out why the fuel mixture is too lean.