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Hello all,

Trying to take ownership of this 92 Seville sts, but it failed it’s california smog test. It drove awesome when I tried it out in city and on hilly highways. It has around 104,800 miles. I don’t know it’s first owner history, but cosmetically it’s near perfect and pretty much runs the same way. Everything appears factory original down to its license plate frames and new owner cassette. No fluid leaks. It’s very precise and responsive whether slowing down or accelerating. I felt nothing unusual except the typical worn front struts. A slight whining sound from somewhere around the engine. Very solid feeling car. The second owner only drove it about 1,300 miles the last two years he’s owned it.
So after my test drive, I brought it back, turned it off after checking for leaks or other odd noises, the battery died. No biggie to me since it was hardly driven I’d expect that. The next day the current owner takes it for smog test so we can make a deal, it fails. The testing station is also his regular mechanic shop, they put new plugs and wires in, still no pass. Last I heard, mechanic thought maybe fuel injector issue. I don’t know this shop, but sounds like he’s guessing more than diagnosing. I myself no more how to change parts than diagnose. Everything was in passing range except the HC level max is 120. It measured 482. Yes, 482. Then the CO max is 1.00. It measured 1.14. Now I know it can often be simple fixes or a major engine issue. But in driving it I felt no noticeable misfires, no hesitations. I took an uphill highway grade that I know some vehicles struggle on and it floated along at 65mph with little effort on my part. No sign of head gasket failure in the fluids. I feel the first problem was taking it for emissions testing right after a dead battery. Besides that I’m just guessing. What do the seasoned experts think? 😸

Thanks in advance.
Robert
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White Diamond '03 DHS (with DTS floor shift)
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First and foremost, pull the DTC's via the onboard diagnostics. Post them AND their definitions and whether they are current (C) or history (H).

Check the two EGR tubes down in the TB. If they are carboned closed, rod them out.
4.9 EGR Tube.jpg
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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Walk. There are other, newer fish in the sea. The emissions failure is a bad omen of things to come.
 

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[Story time]
It reminds me of when I bought my 92 Seville. He wanted CHF 1500 (roughly the same as USD) for it. AC did not work and CEL was on for a MAP sensor fault. The emissions check was expired. He insisted to make an AC refill and do the smog test. He shouldn't have!
AC was R12 so the guy did not want to touch it and emissions failed. He proposed me CHF 500 as-is. The low price let me lots of headroom to fix it as time goes by. The sensor was a two minutes job but finally we ended up changing the catalytic converter which is a pain as you have to cut the pipes and clamp the new one down. The cat was completely gutted, no honeycomb left at all! Car runs really nice now. 92 Seville In really great condition except for one huge key scratch from front to rear on driver side.
[End of story time]
The values at the time were CO 0.812% and and HC 227 PPM. So still lower than yours.
As said upper, It may be the EGR and / or the cat. Does the car's exhaust smell bad like a classic car? Mine was. Also check for codes.
Beware of the front struts, they may be more expensive or hard to get, check accordingly of what you have...
 

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92 Fleetwood 2dr cpe - FWD, 96 Seville SLS, 02 Seville
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Hmm, since the system passed at 2500 rpm, the cat is probably working.

High hc at idle

  • vacuum leak which is more pronounced at idle and more easily compensated for at higher rpm (since you have high co as well, this is not likely as vacuum would cause lean condition )
  • poor spark / ignition
  • leaky fuel injector that is more compensated for unset high rpm
High co
  • evap system stuck open
  • fuel injector
The onboard diagnostics will allow you to church and monitor various components like o2 voltage, fuel trims etc. You can what's out of range
The onboard will also allow you to run a power test essentially turning off fuel injectors one at a time. No rpm change suggests faulty injector (you can use a stethoscope to check if the injector is ticking as well)
 
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