4.2 Timing and Emissions

G

Geos7812

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Joined
Aug 26, 2022
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28
Location
Evergreen, CO
I failed emissions for high CO. I have changed plugs, cap, rotor and oil prior. I have changed the O2 sensor since. Next up I was thinking about timing. If timing is off, could that contribute? I am thinking so but just learning.

Thanks all,

Geoff
 
Your 88 came with a carb unless somebody added FI. The carbs and mass amount of smog equipment are known for poor running and a lack of reliability. Has the smog shop offered any suggestions to why it wont pass?
 
I never could get my 89 to smog in Ca. I’ve had it registered in Az for 20 yrs. I took it to several shops and no one could figure it out. I did not want to keep replacing all the emission sensors or the carb. It runs just fine for me other than the fuel drains down when it sits a few days. Lots of things to chase down.
 
Gilaguy23 said:
Your 88 came with a carb unless somebody added FI. The carbs and mass amount of smog equipment are known for poor running and a lack of reliability. Has the smog shop offered any suggestions to why it wont pass?
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I smog shop yet. I am playing around. Not my daily and it’s a pure toy. Trying to use this a an education. If I get too far down, I will pay someone. I will adjust timing tomorrow and then give it a shot again at emissions.

I am thinking that timing is part art. Getting it to a range and then adjusting for what the engine likes. Is that about right?
 
Yeah somewhat. Most hot rodders advance timing until they get a pinging or predetonation. Thats also on a engine of various hipo mixed parts and no "manual" setting really applies. Octane ratings, elevation, and engine are all factors. In you case frankly running the best you can get it to run is moot as the smog shop needs to see 6 BTDC or whatever you 258 is supposed to have, or it will fail. I once live in commiefornia where the state smogged your vehicle. You fail you go to a mechanic somewhere else where they "fixed" it. Then back to the state smog inspector again. Back then you fail to many times and your dubbed a "gross polluter" and your screwed. Be aware of your states BS laws and Im guessing CO is no better than CA anymore.
 
Thanks for the advice. I just hooked up the light and I do not see a timing mark on the pulley. YouTube showed it as being red and I see no red mark or even a notch on the pulley. Thoughts?
 
The timing covers on engines should have either a raised cast part with 10 BTDC to 0 and then 10 ATDC if its cast or a welded on tab with those numbers. Far as the crank/harmonic balancer there should be a easy to see groove into the metal itself that is TDC. If you have a piece or chalk or some white paint clean up the area and fill that groove with either and you'll be able to see it with a timing light real easily. There is one exception to all this as far as setting the timing and that is its not out of the question that the outer steel ring on the harmonic balancer has slipped or rotated away from where its supposed to be and if you set the timing by it, it will run like crap. In that case a good shop with the high dollar equpt will need to set it using their big buck machines. IIRC a few guys looking for new Balancers and they were not to easily had but that was some time ago. Perhaps the likes of Quadratec, aka China parts inc, has began to repo those too.

258 timing marks.jpg
 
Failed again for high CO. Came down slightly but still high. Next up some sensors and after that, I think I am after a cat.

If this doesn’t work, what are the chances that a fuel injection conversion fixes it?
 
If the cat is shot Id imagine you'll still have issues. I had a Howell FI kit on one of my CJ's. They are not cheap but they do make it run better. A good part of the conversion is GM 4.3 parts so there really isnt any odd ball parts to it if you have a flame out far away from home.
 
So the research I have done says that high CO is due to the engine running rich. My air filter is clean, I have changed Pcv and set the timing. I have noticed that the Jeep is running cool. Do I have any sensors that can be changed to help the situation before I tackle the carburetor?
 
The carbs are notoriously problematic. Been a while since my last CJ/258 but IIRC the mixture is controlled by a stepper motor which can go south. GM used a similar deal on the quadrajets and in my experience they sucked. Most guys do the "nutter bypass" but I dont think its smog legal. Keep in mind a rich engine will eventually damage the cat from unburnt fuel entering it. I really cant speak to any of the rebuilds as far as carbs go, so maybe its time for that FI swap.
 
Gilaguy23 said:
The carbs are notoriously problematic. Been a while since my last CJ/258 but IIRC the mixture is controlled by a stepper motor which can go south. GM used a similar deal on the quadrajets and in my experience they sucked. Most guys do the "nutter bypass" but I dont think its smog legal. Keep in mind a rich engine will eventually damage the cat from unburnt fuel entering it. I really cant speak to any of the rebuilds as far as carbs go, so maybe its time for that FI swap.
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Will the FI swap all but guarantee that it passes emissions? What about swapping the Webber carb, assuming it was adjusted right?
 
Both the Mopar and Howell kits are CARB approved, but I do not believe the weber kits are. Even with a FI kit there is no guarantee. Things like worn engines, a bad cat, Vac leaks, all can contribute to a failure. Does the smogger have anything to say or are they just test/fail shops with no ability to fix stuff?
 
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