Failed Smog. 83 Civic, 115K, Hi NOX


Old 12-12-06, 08:48 PM
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Failed Smog. 83 Civic, 115K, Hi NOX

Thanks beforehand!
This vehicle is new to me and, unfortunately, I do not know the history.

Emissions results: 15mph/25mph: HC 18/15, CO 0/0, NOx 1763/1621
Also failed: Ignition timing: 10 ATDC ,(18 deg.s is spec'd. which makes it a total of about 28 off)

When I bought the car it ran well but would die when idling until after it warmed up completely. I had to have it smogged so a few days before the test I sprayed lots of carb cleaner into the carb and I ran the fuel additive designed to clean out the system and help one pass the test. After using the carb cleaner, while driving, the engine began to race about 4500 over idle. I pulled over, pulled the air cleaner off, checked vac lines, no probs. I rapped on the carb very firmly and it seemed to settle some but only about a 1000 rpm, thus I turned the idle adjustment down. Now, the car still runs fine when driving. However, when I stop, sometimes it runs fine, sometimes it stalls, especially if I stop quickly (automatic).

If I recall, normal operating temp for a civic is for the gauge to be about 1/4 up. My guage runs at 1/2 up at a minimum and often rises to 3/4 and trips cooling fan. I've flushed system, replaced thermostat (spring towards engine), new coolant (50/50 mix), and replaced water pump. Having read your forums I need to check top and bottom hose for temp difference and a visual down the throat for circulation. Still, I don't know thats it's a temp issue as much as carburation.

New oil, plugs, wires, air cleaner, distrib cap., thermostat, waterpump, radiator flush and fluid.

- I've been told that older civics have a passage way underneath the carb in the manifold that often plugs and should be reamed out. (comments)
- Is operating temp on an 83 civic about 1/4 high on the gauge?
- Could solving the temp issue bring success?
- Could correcting the timing solve the high NOx?
- Should I consider a rebuilt carb? or rebuilding the one I have?
- Could the carb cleaner have fried some sensitive parts? Or, did I set something free that needed to be freed?

Thanks again
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Old 12-12-06, 10:06 PM
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I think I would first find out if the timing belt has been replaced. 114K - it should have already been done, if not consider it.

Then make sure the timing is properly set. It really shouldn't be running at all if the timing is off 28 degrees. But I would get it set right. It should make a difference.

Temp gauges don't always give a real definitive measure of the engine temp in terms of degrees. However, it should be within the operating range the gauge indicates. Does the cooling fan bring the temperature gauge back down?

If you're handy with carbs, I would clean what you have first, then replace it if necessary. I doubt if you damaged anything with the carb cleaner. I would take it off and use a bath cleaner on it or at least dismantle it to do a good job. You probably have some parts hanging up with gum and varnish on them.

Hope this helps,

Old 12-13-06, 04:09 AM
Join Date: Oct 2006
Location: Wilmington
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To add to the above, a car that old with only 115K likely has only been driven in the city, stop/go, which is hard on an engines, adding deposits. It needs a long highway trip. Professional help may be needed as some chemicals are not available to the public.
Old 12-13-06, 10:37 AM
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The cooling fan kicks on when the gauge is 3/4 up and runs until guage is 1/2 up, then repeats. Car does ok when driving, long as not stop and go.

Any thoughts on a clogged passage in the manifold? Or the timing adjustment bringing down the NOx. Timing needs to be advanced by 28 deg to be back in tolerance.
Old 12-13-06, 02:11 PM
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28 degrees?!?!!? WOW! I'm surprised it even runs. That can cause havok to a motor. ALOT of unburnt fuel and alot of oil buildup. Get the timing fixed and run a few tanks of super grade gas to clean out all that junk.
Old 12-13-06, 03:01 PM
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Get the timing set first then before you start throwing a lot of money at the problem go to the local Home Depot/Lowe's, etc. and get a gallon of denatured alcohol(about $12.00) wait until you have about 1/4-1/2 tank of fuel then dump in the alcohol and drive it for about 50 miles on the highway then immediately take it to be inspected and don't shut if off until you have to. The addition of the alcohol will make the mixture burn much hotter and cleaner. "DO NOT EXCEED 1 GALLON OR YOU MIGHT BURN IT UP!!!". Have a nice day. Geo
Old 12-13-06, 08:33 PM
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I took it to a repair shop. The guy was recommended and seemed honest. They hooked it up to their machine and said I needed to have the carb rebuilt. I asked if it could possibly be the timing and he said that yes, the timing does need to be adjusted but, in actuality, because the timing is currently retarded by 28 degrees, advancing it will only make the NOx worse. He also said he didn't want me to pay for a separate timing adjustment, that I should bring it in and he'll include that with the price of the carb rebuild. When I asked if it could possibly be the EGR valve or the Cat he said that because the computer (based on the smog test) shows I am putting out zero CO at both 15 mph and 25 mph it's definitely the carb. His print out showed also showed I was running very lean. He did not charge me for the test and said it would be $325 to pull, rebuild and replace the carb. He guaranteed I would pass after the rebuild. I further quizzed him about the carb to be sure he could rebuild it and he seemed to know some of the nuances of older Honda carbs. What are your thoughts. Also, does $325 seem in the ballpark?
Old 12-13-06, 09:18 PM
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Egr first

Set the timing per spec. Check the label under the hood. If that is missing get a book. hose shematic should be under hood too. Someone mentioned timing belt. Check valve timing too. Make sure no. one valves are closed and it is at top of travel at TDC. Maybe somebody screwed it up and set the timing just so it would run. Maybe you when you did the water pump????? had the timing belt off, did you?????

Do you have an EGR system? Not all cars do. My ’93 Protégé does not and my ’84 Vanagon did not, but my ’78 VW bus did. If you have one, remove the egr valve and start the car. If the runs normally the passage you spoke about is plugged. If it won't idle, put the valve back on. Start the car and open the valve with a vacuum pump. If the idle turns to crap, your egr valve and passages are perfect. If idle does not change replace the egr valve. Then check vacuum control hoses and control solenoid. Remember you should have no EGR at idle.

I don't know if I buy the lean theory. It would run poorly and you said it drives fine. Super rich conditions may make CO higher since you have a high carbon to oxygen ratio. It is true that a lean engine runs hot, so most air-cooled vw’s are jetted a bit rich. I cannot see your car running so hot that it causes this problem. I don’t think it is your carb.

The egr systen reduces NOx and allows designers to advancing timing more without knocking. I don't hink the reverse is true: less advance (retard) = more NOx. Although, with less advance you get less power and will, in theory, use more gas (hotter) and compensate w/ your right foot.

Nx is produced when the Nitrogen in air is exposed to high temps and pressures. The egr system is designed to reduce both by intruding non-reactive exhaust into the mix. The CAT helps by reversing this reaction too. These are combustion chamber temps not coolant temps. If engine was too hot, you would warp alum heads and dstroy rod bearings w/ thin oil.

Last edited by peabees; 12-13-06 at 09:40 PM. Reason: missing info
Old 12-13-06, 09:59 PM
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The timing spec is under the hood and I will set it according to spec.

The car does run good when cruising, but when stopped it idles poorly and often dies. Would this point to the carb?

Also, what are your thoughts on the CO levels being zero at both 15 and 25mph?

Does $325 sound ballpark for a carb rebuild?

What questions should I asking regarding the rebuild so my bases are covered? Again, he seems trustworthy.

The EGR valve, according to the manual is "Under hood, center, rear engine area, below valve cover, mounted in intake manifold". Hmm, mounted in the intake manifold, sounds more complicated to get to than most.

Finally, regarding the comment to run a gallon of denatured alchohol through the system, thats great if it may clean out my carb, but in truth, I don't want to beat the system, I wan't to correct my problem- will this help clean the carb or could I do more damage?

Thanks again!
Old 12-14-06, 09:02 AM
Join Date: Jun 2006
Location: St. Louis
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The alcohol will help clean the carb. After checking with, which only goes back to 1986, a 1986 Civic dx hatchback w/115k miles is only worth $725(private party, good condition) with all the stuff you have already done you are starting to create a money pit. Have a nice day. Geo
Old 12-14-06, 11:12 AM
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Wow, you guys are looking out for the good of the community thanks for the homework on the cost/benefit. In fact, that's the question I'm asking myself. At the same time, I intend to post it on ebay where the honda classic collectors will pay quite a bit more. But, is it worth rebuilding the carb at $325 and still not knowing if the investment will solve my problems. . .

Old 12-14-06, 12:12 PM
Join Date: Jun 2006
Location: St. Louis
Posts: 2,354
If you don't plan on keeping it, in my opinion, no it's not worth the money. Most people who buy the classics are going to redo whatever you have done anyway to make it how they would like it to be. Have a nice day. Geo
Old 12-15-06, 03:54 AM
Join Date: Dec 2001
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would set your timing first and if it is really that far off which would be hard to believe that it would still be running decent, so dont really expect it to be that far retarded, but retarded timing will increase the temperature of the exhuast which will increase nox.
wouldnt bother with the alcohol it is a band aid to pass the test alcohol burns cooler than gasoline wich will reduce nox but it can be hard on the fuel system it draws moisture and promotes rust and corrosion and can damage carb parts in a high enough concentration.
if your still having drivabilty problems after setting the timing 325 is not to bad of a price to rebuild the carb you might check around a few places but its getting harder to find a mechanic that knows how to actually rebuild carbs instead of just replacing it.
Old 12-15-06, 01:44 PM
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Thanks everyone for the insights. I'll let you know how it turns out.

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