91 Wrangler failed emissions

When was the last time it got a new distributor cap and rotor or wires?

Cleaning the air intake (fuel induction system) sounds like you have an oil blowing into the air filter issue? If so, there are fixes for that.

Fresh oil and air filter is always a good thing too.

Your O2 is likely due for a change. Does that 91 have the Renix computer or the Chrysler one? If Renix, the O2 is a recall part.

What were your readings? High HC's?

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 'New' frame in the works for '08. Some Canadian Bush Trip and Build Photos:

Mike, It's been a while since I've changed the cap and rotor. I tried doing it last month and could not loosen the screws on the cap. I was afraid of stripping or breaking them. So I changed the wires and plugs only.

I've read other posts about oil in the air filter, and have never seen any.

I have not picked up the readings yet. Will any of the readings point to the catalytic converter as the issue? It is original.

Regarding the induction service. The shop sent me a link to bgfindashop.com. I've heard lots of good things about bg products, but was curious if this was necessary.

Thank you, CTM

You need the readings.

Mike

Sorry to hear that you've failed your emissions inspection. Before you fix anything, it is important to know why you failed.

Can you provide some numbers? Was your HC count high? At idle? At speed? Can you provide the numbers or even better, a photograph/scan of the actual readout? This would help tremendously.

Changing oil, cleaning fuel injectors, filling up, praying, installing fuel line magnets, sacrificing a virgin at an alter at Midnight during a Full Moon, etc. won't help.

Get a 3-mo. registration extension from DMV, then get more information before proceeding. It's probably something very easily repaired, so don't panic. And don't let the testing facility do any repairs. If they were competent, they would already know what the problem is.

I've posted the numbers to

Any incite would be appreciated.

CTM

Interesting. High CO and NOx readings and okay HC's. Assuming that you don't have severe overheating or pre-ignition problems, this should be easy to track down.

Before retesting, have a mechanic check the following, in order of likeliness:

EGR valve malfunction (if applicable) Incorrect ignition timing (overadvanced) Worn catalytic converters Excessive combustion chamber deposits Worn timing chain (incorrect valve timing)

If you live in CA, the state will give you $300 toward repairs, but you must have it done at an authorized facility and you must get pre-approval before work is done; forms are available at the shop.

You don't want "incite" for this, heh. You want "insight". You will get plenty of both in this group. Replace rotor, cap, and plug wires. Clean or replace the PCV or CCV system, whichever it has. "Induction service" is a nice touch, but it won't help your numbers. A clean air filter will do that. It is important to get the vehicle running as well as possible, before the test. Guys in Fort Collins let my Land Cruiser warm up real good, after it failed on a cold engine. With your CO numbers like that, you problem is basically nothing more, than that your engine runs like crap now.

Earle

I would get a 'good' penetrating oil, something like PB Blaster or even Liquid Wrench and soak the crap out of those distributor screws. They 'do' snap really easily and drilling them out for a nut and bolt is sure a pain.

The distributor affects the timing and spark and the only 'fix' you have there is the cap and rotor, the timing isn't adjustable on that engine.

If you still are running the original O2, it can't hurt to change it.

The induction clean helps for high HC's which is why I was asking about oil spits into the air filter. the induction cleaning 'did' help our 88

4.0, but it was totally soaked in oil after the usual failure of the CCV system. (blocked rear line)

A good run at high rpm, like keeping it in 3rd and 4th with some 'hard' acceleration on the on ramps on the highway or a good high rpm off road run in 4 low will help to blow any buildup in the combustion chamber which might be contributing to the high NOx. Does it ping under load or run on after you turn off the key? If so, another 'fix' might be in order, a carbon clean.

And after that, if it still fails, I would go for a Cat I guess.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 'New' frame in the works for '08. Some Canadian Bush Trip and Build Photos:

The CO is high because the engine is running poorly. An ignition tune-up should fix that. I think (hope) that the NO readings will come into line once the engine is running properly. The cat won't function properly unless it is at the correct operating temperature. The NO is marginal and can hopefully be fixed by properly tuning the engine, without a new cat. It is an error with gasoline powered vehicles to look for performance problems anywhere else, unless you are 100% confident in your ignition system components.

Earle

ing. High CO and NOx readings and okay HC's. Assuming that you don't

If the ignition system were malfunctioning, his HC would be high, and the cats would likely be toast from overheating.

High CO/NOx levels are always due to unusually high combustion chamber temps; NIH (not invented here) is taken care of downstream at the cats. There are a variety of reasons this will come up high, but some careful sleuthing will find it.

A good article on this can be found at:

I'm pretty good friends with an ASE-type who owns his own smog-check shop. Most of the time, this is simply a plugged or non-op EGR valve. Second most common problem are guys who noodle with their timing, overadvancing it too far.

I just looked it up, you 'do' have an EGR, I didn't think you did. I would remove that and clean it. A really good soak in carb cleaner does that valve wonders.

Original post says "It's been getting bad mileage for a while." Like I said, it is an error to do anything until you assure yourself that the ignition system is up to par. Age and frozen distributor cap screws says this stuff needs replaced. I'll bet the plug wires are original. "Careful sleuthing" is a cute phrase, but it is no substitute for conscientious maintenance.

Saludos,

Earle

Bingo! I agree with Mike: remove the EGR and clean that sucker with carb cleaner and a stiff brush, and be sure that the passageways are clean as well. Install a new gasket upon reassembly. If the hose(s) that connect to it are worn out, replace them.

Around here, techs check EGR operation before even beginning the exhaust testing because EGR valve failures are so common.

Believe it or not, the #1 reason that EGR valves do not function properly: aftermarket junk! Yes, it's true. People often replace their EGR valve with aftermarket parts that flat-out don't work, right out of the box. Those in-the-know *always* replace EGR valves with OEM parts, regardless of cost.

I'm guilty as anyone on this. I once replaced an old, worn-out EGR valve on an old Chevy-Beater with $60 aftermarket junk. 6-months later, I failed a smog check, and to my surprise, the EGR valve came up non-op. The tech explained to me that most aftermarket EGR's are junk, and that replacing it with an OEM valve would take care of the problem. $46.00 and one OEM EGR valve later, it passed with flying colors.

Imagine that. Expensive, aftermarket junk that cost me more money that it was worth in retest charges. Want to know how much money aftermarket parts suppliers get from me these days? NADA. To hell with 'em.

Funny that this sort of part is "always" out-sourced, and the OEM and aftermarket parts are usually identical. A bad EGR could raise combustion temperatures, especially at the 25 mph setting, but that is not going to explain the OP's bad gas mileage complaint. Fixing the emissions while the car continues to run like crap and burn too much gas is like pissing into the wind.

Cheers,

Earle

The Earth is round.

A 1991 4.0L Wrangler doesn't have EGR. A 1991 4.0L Wrangler doesn't have adjustable timing. High CO is caused by a rich mixture, NOT high combustion temps.

Look this guy claims to know someone who is ASE certified. I can't top that. I wouldn't know anyone who was ASE certified. I just have a degree in Physics, how lame is that?

We figured in 1978 when I was working in the Dodge garage that emissions controls like EGR were just a scam to make the tree huggers think something was being done. It turns out we were right. EGR lowers combustion temps and inhibits formation of NO, but the cat does all the work in getting rid of it. CO is a combustible gas, ergo high temperatures make it burn, duh. The PCV valve was a good idea, computer controlled fuel injection was another one.

Almost forty years experience tinkering with cars says that a properly tuned engine burns cleaner and uses less fuel. Trying to get emissions controls to work on an improperly tuned engine is like pissing into the wind. I have consistently gotten well-tuned vehicles to pass emissions certification, with the EGR and various other Rube Goldberg devices removed. It's not hard. If your state does a visual, then disable the offending device in one way or another, but leave it in place. That's not hard either.

"Even a fool, when he holdeth his peace, is counted wise: and he that shutteth his lips is esteemed a man of understanding." Proverbs, 17:28.

"When a fool helps, the more he helps, the worse things get." Chinese proverb.

"The fool learns by suffering." Hesiod, Works and Days, 216.

"Doctores indoctos, nunca hubo pocos." F. Caudet, Mejores refranes españoles, #2545

Cheers,

Earle

"ASE certified" only means he passed a multiple guess test. I've known "ASE certifed techs" that I wouldn't allow to put a spark plug in my lawn mower, let alone diagnose a bad plug to begin with.

EGR came along before the cat converter did, and it works. Until they started using three way cats, the cat didn't to anything to reduce NOx emissions.

Early EGR systems left a lot to be desired, but controls are a lot better today. In fact, some vehicles are equipped with EGR because they actually get slightly better fuel mileage, not because they needed it to pass emission standards.

I agree with the properly tuned part. Emission controls are designed to work on a properly tuned engine. However, in California, if you're not doing an ASM (loaded mode) test, a functional test of the EGR system is required. Sometimes just "being there" isn't enough.