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SMOG STORY

desertvet

NAXJA Forum User
Location
Bishop, CA
Hi all XJ owners! I am posting this to hopefully help the next guy with similar troubles. This web site has been a god-send with good information and ways to trouble shoot issues, now the rest of the story:

About a year ago I purchased a 1990 XJ. It ran, rough and leaked like a sieve. After several hours searching on this web site I came away with a list of things to check and ways to trouble shoot my Jeep. :dunce:

After a little tinkering I think the jeep is ready for smog so I take it to the local guy and it fails terrible with high CO and HCO (running rich). Again I came to the web site and got a lot of info on what the cause might be: temp sensors, map, egr, tps, crank, ect. I checked and checked and could not find a problem with my Jeep. So off to the mechanic it went, $700.00 later all I had was a “Gross Polluter” that ran good, started every time but was useless here in CA. I paid the money and took the Jeep home to ponder why I had just paid $700.00 for a smog test and a mechanic to fix it and neither had happened. :dunno: More searching! :geek:Well let’s get back to basics, new plugs, wires, CAT, distributor, ect. How about a compression test, oh no two cylinders with 85 and the rest not higher than 115. Time for a new motor! :idea:

After pulling the motor I pulled the head and found Antifreeze and rust at one of the cylinders. Wait, didn’t I just pay a guy a lot of money to check stuff like this?:wstupid:

Several months later with a fresh engine back to the smog guy! CRAP!!!! Same problem, this does not make sense! After a lot more trouble shooting and money in sensors and general checking (I was not going back to the smog guy) I finally find another guy (a friend this time) with a scan tool which works on the old Renix engines. Three days later, problem found! Faulty wire to the O2 sensor (broken connection), Kragen temp sensor not working properly (put OEM in), and broken ground wire (repaired).:clap:

Along story short, the computer was in open loop, meaning the computer was not managing the engine, just staying in cold run mode, hence the high CO and HCO. Once all the fixes were done the engine comes up to temp and leans it out like it is supposed to, runs great and passes smog with flying colors. :yelclap:

Thank you all for posting here, it helped me a great deal. For anyone else having smog trouble, a mechanic with the right scan tool is imperative to check operation parameters of the engine. There is no other way to systematically check all the inputs into the computer.

Thanks all,
Brian
 
Sorry it took you so long to get where you needed, glad you have a passing XJ now. NAXJA is a valuable resource indeed.
 
Not that I know of. The tool does not check anything, but it allows the user to monitor the sensor to see if it is operating with tolerance.
 
sorry, didn't see you weren't washington. The testers here are not allowed to perform repairs and if you fail and go to a qualified repair facility spend $300 and fail again you get a waiver and your tabs anyway.
 
Well the ride is finally legal and registered!party1:
I have a little fine tuning to do on the chasis, 3 inch lift, bumper, a little wiring, ect.
 
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