hey smog gurus

So I smogged my xj some odd weeks ago and failed.
15mph. Hc max 62. Meas 61
25mph hc max 38 meas 44

I knew I had a cracked exhaust manifold so I dove in and replaced it, also swapped in the ford 19lb injectors. Drove it around a few days and got it smogged again today and failed again.

15mph max hc 62 measured hc 41
25mph max hc 38 measured hc 39

Failed by 1 stinking point. I'm leaning towards a tune up, probably due. The let one was about 2 years ago. The cat is in the back of my head, as far as I know its a stock one with 200k miles on it. Any help would be great, that way I'm not sitting here throwing parts at it. 93 4.0 if it helps.

I usually replace the O2 sensor and the MAP sensor, you can see what those two sensors did to my jeep a few weeks ago http://naxja.org/forum/showpost.php?p=244887496&postcount=21

was it at operating temp when you took it in? personally ide change the plugs! but sea foaming it will probally fix your problem!

HC is unburnt fuel. Ie running rich. I'd toss a tune up on it and an O2 as that controls the mixture. Hope you don't need a cat, as you can't buy them anymore in Cali... Gotta have a "gold certified" shop replace that.

you can buy cats i tossed one on myself on the last jeep after the law passed they only sell the new and improved ones though there 4 stage i believe. and like twice as much as the older versions. but you can still get them!

change the plugs! At the very least pop one out and look at it. if the either the center electrode or the arm is not squared off on the edges you should replace them. it should look like a new pencil eraser, not round like a used one.

I doubt it is the cat, your numbers would be way off instead of just barely not passing.

There is no way to tell the cause of the failure simply by the failed emission. Each emission has an effect on other emissions. If the vehicle failed for Hc and the other emissions are low then you may have a tune problem or a vacuum leak. If Co is also high, then you have a rich problem. A rich problem will also cause NOx to be very low because the extra fuel is lowering combustion temp. If HC and NOx are high you may have a lean problem, an exhaust leak or a bad Caytalytic Converter. You should plug your emission numbers into a Lambda calculator (google search) The closer the result is to 1 the better. Lambda of 1 means that the vehicle is in fuel control, and you don't need a n O2 sensor lambda higher than 1 means the vehicle is lean. Lambda lower than 1 means the vehicle is rich. If the vehicle is in fuel control you may want to look at the Catalytic Converter. The only way to accurately diagnose a cat is by doing a cranking CO2 test. This requires a 4 or 5 gas analyzer. If you have exhaust leaks they can cause the cat to stop working. If you have exhaust leaks for long enough they can destroy the cat. All catalaytic converters installed after 1-1-09 must be OBD2 compliant, whether it is an OBD2 car or not. They are widely available in the aftermarket and range from $100 nto $200 depending on the cat. The design is no different than older cats. They are a 3-way cat with a reduction bed and an oxidation bed, the quality control is just more strict now.

Change the oil!

Tune-up plus plugs, make sure your plug wires are still good.

Run it on the freeway good and hard before you take it in next time.

You're close enough to passing (just the mildly elevated HC level,) that that should sort it.

Seafoaming optional (won't harm anything if you do it. Make sure to disconnect the exhaust and pull the cat out of the way - if you do free up a bunch of carbon deposits, you won't want them coating the matrix in the thing...)