I've got a 93 bronco with a 302. I can't get the thing to pass emissions. I have tried all the tricks in the book- alcohol, gas treatment, etc. Anyone know what I could do to get it to pass?

 

Depends, how many miles are on the engine, and has it ever been rebuilt?
What was the failing aspect of the smog test? Too much CO or HC? Or both?

Chances are, if it has high miles and never had a rebuild, you may need to have the top end rebuilt and if you're burning oil past the rings you might need a ring job too but there's a few things you can do first.

I would do a compression test and be sure all cylinders are close, I think the lowest cylinder has to be at least 75% of the highest cylinder. (ie: if your highest cylinder read 100psi, your lowest shouldn't be below 75psi, I don't know the actual pressure of the cylinders I'm just doing easy math)

I think the trick is to put a teaspoon of oil thru the spark plug hole and if the reading is better that means your valve guides need replacement. Never tried it but it's mentioned on this board.

I just did a rebuilt on my top end, found two cracks, one on #3 and one on #4 between the valves (causing my backfire) and of course the head gasket blew on #4 causing coolant to leak into the oil. I had the cracked head replaced (shop had one on the shelf and let it go for $100) and with parts/labor I was out the door for $495 and I got hardened valve seats, new guides and they were both rebuilt to spec. Price varies from shop to shop, but if you need to have it done do it to both cylinder heads and pay for the full gasket set (got mine on PartsAmerica.com) so you can replace your thermostat gasket, intake gaskets, exhaust gaskets, water pump gaskets, etc... Unless you have a shop do it. To do it myself it cost me about 5 to $600 in parts (bought a new water pump while I was at it, and a smog pump) and about two Sundays. Now I'm having to take the intake manifold back off because my buddy didn't use enough RTV for the intake manifold seal and I have a leak, so I'm gonna use the cork gaskets instead like I should have done.

If you do it yourself, get a good repair manual, take your time. Haste makes mistakes.

Without knowing what your readings are I'm guessing you have high miles or possibly your emissions equipment isn't working as advertised. You might need to check the EGR valve for blockage or leakage.

Post your emissions test results so we can go from there.

 

You need to stop and check for codes before you go any farther. Your CEL may not be on, but that does not mean there aren't any stored codes

 

Taking it a knowledgeable shop to have a tuneup, perchance?

And depending on what and how failed, there are different ways to fix it.

 

no, it means your piston compression rings are worn ...we really need to know what part of the test failed it...it could be a number of things...high milage engines may, and do burn oil...you may have one of many sensors sending a false reading to the engine control module, causing a rich condition...your catalytic converter may not be doing it's job...your egr valve may be in a stuck open position...etc, etc, etc...and pulling the codes is not always going to lead you in the right direction...

i agree with aurgathor, take it to a knowledgeable garage, and have them sort it out for you...even though there is plenty of very smart, and experienced ford truck gurus on this board, your problem brings up a lot of maybes...

 

You're absolutely right, my brain was working dyslexically. (is that a word?)

I agree, a shop would save time and money if all you can do is throw parts at the truck and not really be able to diagnose the problem.

 

I would consider this the BEST advice. No point trying to "get around" an emissions test unless you have (pardon the pun) exhausted all of the options. If the EEC computer has stored codes thats the place to start. Its whole function in life is to monitor and properly control the fuel, induction and ignitions systems for optimal performance and still retain the emissions requirements for the truck. Any fault codes are indicative of a problem that will most likely affect your emissions. It will also save you time and money replacing/repairing things that may or may not be at the root of the problem.

 

Exactly.....this is the place to start....check for codes. Make sure all the major tune-up items are new....including the o2sensor, IAC and TPS are working 100% or replace them. Give her a shot of sea foam.......and if it still dont pass, hit the guy off with $50 and be done with it.

 

The first 3 times it failed on CO. The 4th time it failed on both. The CO was 680(400 is legal) and the HC was 4.8%(4.0% is legal). I replaced the TPS and had a highflow cat installed before the last test. And yes it has high miles, 196,000.