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OBD II Questions

bjoehandley

NAXJA Forum User
I just got my Emissions notice today, other than the gas caps, what should I worry about? I've got an '98 Limited with 4.0L/AW4/242/3.73 gears and a tow package. It hasn't thrown any lights my way, but I'm wondering what to look for.
 
just out of curiousity what is the problem with the gas cap
 
Sorry about not posting the state, I remembered that after I got off the computer. I live in Illinois, more closely the western suburbs of Chicago. This is our first and only OBDII compliant vehicle currently in the driveway.

Before I forget I also just installed Bosch Platinum spark plugs, Mopar Performance 7.5mm wires, drop in K&N filter, stock replacement Mopar Parts cap & rotor, and normally run Mobil 1 10w30 in the crankcase.

As for the gas cap, while talking to the parts guy at a former "official" Jeep dealership (still one of the best places to go in this area though), that for some reason, older gas caps seem to fail the Illinois Air Team gas cap tests. I never had that problem with the K-Cars I've owned, none of the other Jeeps we've had, and Mom's haven't had that problem either.
 
bjoehandley said:
Sorry about not posting the state, I remembered that after I got off the computer. I live in Illinois, more closely the western suburbs of Chicago. This is our first and only OBDII compliant vehicle currently in the driveway.

OBD-II shouldn't affect how you take it in for testing or how it's prepped for it.

Before I forget I also just installed Bosch Platinum spark plugs, Mopar Performance 7.5mm wires, drop in K&N filter, stock replacement Mopar Parts cap & rotor, and normally run Mobil 1 10w30 in the crankcase.

If you've put any fuel system cleaner / octane booster / other additives in the tank, run that tank to empty, refill, and run at least half a tank of pure gas through the car before you take it in for testing. Additives have been known to cause tailpipe failures.

As for the gas cap, while talking to the parts guy at a former "official" Jeep dealership (still one of the best places to go in this area though), that for some reason, older gas caps seem to fail the Illinois Air Team gas cap tests. I never had that problem with the K-Cars I've owned, none of the other Jeeps we've had, and Mom's haven't had that problem either.

I've got a late-'70s Renault with a similar issue: the DOT-approved OEM fuel cap that it has physically does not fit the modern adapters used to test them. When it needs smog, it gets a radiator cap in place of the factory gas cap and everything's fine.

Gas caps do lose sealing efficiency over time. A worn gasket or threads can cause a failure once it's put on the tester.
 
I just ran a tank full of 100% 2 weeks ago, and probably still have some in the tank, just heavily diluted from the last couple of fill-ups. I ran some cleaner through it about 3 weeks ago, before the trip where I bought the 100%. I guess now they plug into the onboard computer to look for fault codes in the computer, as well as the gas cap test. I don't remember if they stick it on the dyno and stick a probe up it's tailpipe, I haven't had to take anything in since April '02, and never paid attention to newer cars (I tend to keep an eye on mine so they don't destroy it by accident, since if they do damage the car, it's not their fault and repairs are supposed to come out of the car owner's wallet)
 
bjoehandley said:
Sorry about not posting the state, I remembered that after I got off the computer. I live in Illinois, more closely the western suburbs of Chicago. This is our first and only OBDII compliant vehicle currently in the driveway.

Before I forget I also just installed Bosch Platinum spark plugs, Mopar Performance 7.5mm wires, drop in K&N filter, stock replacement Mopar Parts cap & rotor, and normally run Mobil 1 10w30 in the crankcase.

As for the gas cap, while talking to the parts guy at a former "official" Jeep dealership (still one of the best places to go in this area though), that for some reason, older gas caps seem to fail the Illinois Air Team gas cap tests. I never had that problem with the K-Cars I've owned, none of the other Jeeps we've had, and Mom's haven't had that problem either.

Generally, in Illinois with OBD-II, they are just going to hook up a reader to the vehicle computer. If the computer has recorded any fail codes, then they might do the sniffer test, or they might fail the vehicle (if the check engine light has not come on, then you are probably good to go). They will check to make sure that the check engine light functions, and if you have disconnected power recently (if the computer reports a loss of power and no other codes are stored), they may fail you - you just need to make sure you have several start-run-stop cycles on the computer before you go in.
 
Thanks Djinn, that's some of what I was concerned about. That hasn't been done for a while, so I ought to be ok on that. I may need to have the AC compressor replaced but I'll have that taken care of after the test.

Any recomendations as to which station to hit here in the Dupage/Kane Co. area?
 
In OH as well, if you have OBDII (96+) they dont do any test except check the computer for codes. Something to keep in mind is you don't want to do any sort of work that would reset the computer just before the test because the 'recent reset' code will fail you even if there is nothing wrong.
 
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