My 86 CJ7 failed Virginia's strict emissions test, I need advice on how to get it to pass. I can do mechancial work myself if I know what to tackle. Here are the specifics: 15 MPH Test 25 MPH Test HC (Limit/Readings) 207/50 Pass 201/298 Fail CO 1.76/.01 Pass 2.29/4.69 Fail NO 3010/2192 Pass 2796/215 Pass RPM 1926 Valid 1279 Valid Dilution 14.9 Valid 16.8 Valid
Visual components and smoke inspections passed. Thanks in advance for any hints you may be willing to offer. Dan
Just found this on a website:
CRUISE EMISSIONS At cruise, the engine is lightly loaded and running at high rpm. Under these conditions, HC and CO should be low if the oxygen sensor and feed back control system are working properly, and the catalytic converter is in good condition.
High CO readings during cruise indicate a rich fuel condition. Causes here may include: . Defective O2 sensor; . Exhaust leaks upstream of the O2 sensor (check manifold gaskets and air plumbing connections); . Defective AIR pump or diverter valve (also loose or damaged air pump plumbing); . Defective MAP, MAF or VAF sensor; . Float level and operation (older carbureted engines); and . Power valve operation (older carbureted engines). High HC during cruise would indicate a steady misfire or loss of compression (leaky exhaust valve).
This should give you some things to check for. Also, because it seems you are running rich, check the air filter and choke for proper operation. I would also check to make sure the EGR valve (if it has one) is functioning properly.
Chris
EGR valve comes to mind, but those readings could just indicate the need for a new air filter or a new cap and rotor.
When was the last time the plugs were changed?
Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT'sYour CO reading is the one that is telling. You are burning too much fuel at cruise, and this is due only to fuel delivery. The other guy had it nailed, check the air filter and choke, then you are looking at carb work. No external adjustments for this, you probably have a sinking float. Don't waste your money on a bunch of plugs and wires, and don't buy a catalytic converter. The converter will make it pass this year, but by next year, all of that excess fuel will destroy the catalyst and you will be back to rebuilding the carb again.
Also, don't worry about the high HC readings during cruise, as they are a by-product of the high CO rate. Fix the CO, the HC goes away.
Jerry
Too rich @ 25 MPH. Possible carb problem, malfunctioning feedback system or dirty air filter.
Don't be surprised to see a higher NO number when you get the mixture leaned out.
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