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Old 07-10-2013, 06:59 PM   #1
Join Date: Apr 2013
Location: Phoenix, AZ
Posts: 118
4.2 Not Passing Emissions

Hello all. I have a 90 4.2L. Weber 38/38, nuttered and team rush upgrade (except the ignition upgrade).

My initial test for emissions showed me running at 41 CO/1.83 HC/3.6 NOX. After finding out that the PO who did the Nutter bypass did not retime the engine I set the timing to 12 BTDC which is where it has the best power and smoothest idle. I know 8 is recommended but this engine has 200k miles on it and it is worn out.

After the timing I ran through testing again and the test came back much better. 25.71 CO/.26 HC/1.98 NOX but still did not pass the Arizona standard of 20 CO.

My vacuum is fine. The EGR valve is brand new. The carb is in good shape and has been jetted down. All smog gear is hooked up and working.

I still am getting a constant misfire several times a second. It idles well and it's not much of a miss but I can still hear it. It does smell like it's running a bit rich. The 2 Weber mixture screws are at 1 1/4 and 1 1/2 which is only 1/4 and 1/2 out from the starting point. According to the huge amount of reading I have done on this carb means that the jets are the correct size.

I need help. I only have 5 days left to get this to pass.

1990 YJ 4.2L
Currently in the shop for an 8.8 swap!
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Old 07-10-2013, 08:53 PM   #2
Join Date: May 2013
Location: Tyler, TX
Posts: 265
I am lucky and don't have the tailpipe test in my county, just the visual inspection. I always read the emission posts for some reason. I have read that changing the oil and running the Jeep at hiway speeds for 20-30 minutes will help. I assume this gets the catalytic converter real hot to burn more off. I would also try some of the fuel additive that says it will help pass the inspection. I think Amsoil makes one. I dont know if it works, but the right chemicals could help the ignition of fuel. The $50 handshake never hurts either(that is a joke, I would never recommend doing something unethical).

1989 YJ, 4.2/TF999
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Old 07-11-2013, 10:50 AM   #3

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Location: North Las Vegas
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89 2.5 TBI, 4" RC lift, 1" Booms, SYE, Adams Driveshafts front and rear, Ford 8.8 with 4:88s, BFG 33X12.50X15, and a ton of other stuff.

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Old 07-11-2013, 11:23 AM   #4
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I would adjust the fuel mixture again. When I had a slight problem with my 89 all I needed to do is replace the spark plugs and it passed. There were approx. 12,000 miles on the old ones.
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Old 07-11-2013, 11:58 AM   #5
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Join Date: May 2013
Location: Cardiff By The Sea / Glamis
Posts: 1,183
How are your spark plug wires? Mine were arcing against the block intermittently and would cause some stumbling.
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Old 07-12-2013, 11:21 PM   #6
Join Date: Jan 2013
Location: CA
Posts: 684
Try checking this site for tips: Recarbco Carburetor Smog Diagnostic Chart
1990 Wrangler 4.2L
Howell TBI, 2.5" OME springs; OME Nitroshocks; 5/8" OME shackles; Swaybar discos; 31" tires/15" rims
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Old 07-13-2013, 02:11 PM   #7
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Join Date: Jun 2013
Posts: 568
or just get it exempted for now. you have to drive your truck under 5000 miles per year. most 4.2 with weber's don't pass.
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Old 07-13-2013, 04:28 PM   #8
Join Date: Apr 2013
Location: Phoenix, AZ
Posts: 118
I got pulled away from the jeep for a couple of days so I'll be back into it tomorrow. I just replaced the spark plugs (auto lite copper at .35" gap). Plug wires are Autolite 1981 ford i6 with the team rush upgrade. I did not upgrade my ignition when I did the team rush.

This jeep has been running for at least 2 years under rich conditions so I'm thinking the cat is bad. If I'm going to get it to pass I'm pretty sure I need a new cat. I also have some broken welds on the muffler which is causing an exhaust leak.

I might look into an exempt status because i only drive about 3k miles a year. The jeep is new to me but I barely drove my pickup. I travel for a living and I usually get a ride to the airport.
1990 YJ 4.2L
Currently in the shop for an 8.8 swap!
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Old 07-24-2013, 11:54 AM   #9
Join Date: Apr 2013
Location: Phoenix, AZ
Posts: 118
A new cat and muffler got me through with 8.61/20 CO. I passed!

1990 YJ 4.2L
Currently in the shop for an 8.8 swap!
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