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How to lower emission hydrocarbons?


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05-06-05, 06:46 AM   #1  
MJE49
How to lower emission hydrocarbons?

I have a 1987 Jeep Cherokee, 4 cylinder with 189,000 miles. Last month it failed a required emission test because of high hydrocarbons. The reading was 3.63 and the requirment was 2.20. Co and NOx were below requirements. Are there some farily simple things that I can try that might lower the HC to the acceptable range or is this something that will require a certified mechanic.

 
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05-06-05, 09:28 AM   #2  
are you sure that it failed hc as it is usually measured in parts per million and there usually is no decimal point in the number.
if it is hc check for vacum leaks, changing the oil may also lower it a small amount.

 
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05-06-05, 09:55 AM   #3  
MJE49
bejay, sorry, those numbers are in gpm. I tried to do some researching on the internet and I had read where the oil change might help, as well as new plugs, plug wires and rotoray cap. Just looking for all of the ideas that might help and wodering if they are likely to get em below the required standard. Thanks

 
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05-06-05, 10:16 AM   #4  
hc is unburnt fuel and things that impact it the most would be a lean fuel mixture or vacum leak or if its missfiring at all,your hc will be high, if it is carburated it could be a carb related problem, they usually take readings at idle and at above idle rpm did it fail at both rpms.
not familiar with gpm so cant really tell from those numbers how far it is off changing the oil is a good idea to have done just before you take an emmision test as it can often put a vehicle just out of specs depending on how long it has been since its been changed.

 
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05-06-05, 12:07 PM   #5  
MJE49
bejay,they put the car on a tredmill like and drive it. IF I am reading the chart correctly, at the higher speeds it was below the standard, but when they let off of the speed, it would spike above the standard. Thanks for your advice.

 
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05-07-05, 06:33 AM   #6  
How does the vehicle run? Are u experiencing any problems other than it won't pass a test?
I would try another test facility first.
If it still fails, definitely change the oil. Don't bother with the tune up yet.

 
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05-07-05, 09:25 AM   #7  
sounds like you are in cal. to me. Where since jan 05 they require the car to be on a dynomometer while testing to simulate actual driving. My experience with getting my cars to pass is:change the oil, put in new plugs, make sure its running great(if there is a vacuum leak,or missfiring it will do horribly), retard the timing to the lower limit, and on my toy corolla the top of the valve cover where the blow by went through If laquer thinner cleaned would drop hc's from 330 down to 50. Amazing but true. New catalytic converters can help but have'nt been as effective as getting the car to run right.

 
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05-07-05, 09:46 AM   #8  
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bigguy, car runs good for age and mileage, doesn't miss that I can tell. The only problem I have encountered has been that some times it will idle fast and some time slow. However, I only use the car to go fishing or were I'm going to be in a muddy area. I probably don't drive it 1000 miles a year. That is the only test facility in my county. In Indiana the test facitlities are state operated.

jeff, are you talking about the pcv valve?

Jay

 
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05-07-05, 01:12 PM   #9  
popps
You have a jeep cherokee, there are tons of vacuume lines on them. Did you check to see if you have a line leak anywhere? A line is leaking if you plug it, and the idle goes up. YOu most likely have alot of blow-by, try a new pcv valve too. Of course check the tune-up too on it like the above posts said. I personally like to weld a new converter on if there is any question that it will fail emmisions. Aftermarket one is about $75. Yup the treadmill is a pain, also make sure your back brakes are tightened up too, (star wheel) and the brake pedal feels solid.

 
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05-07-05, 04:08 PM   #10  
MJE49
popps, thanks.

 
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05-08-05, 01:32 PM   #11  
IF you only drive 1k miles a year, chances are the excess gas is in the crankcase. Change the oil. Although, I am not even sure if that veh. is carb or fuel injected, so I shouldn['t even post any more in this thread, but if it's got a carb, and it idles high at times, that means the choke is stuck possibly, and that would definetly cause a failed hc test.

 
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05-08-05, 03:55 PM   #12  
MJE49
Bigg, it has a Throttle Body, which I assume means it is fuel injection.

 
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