79 emissions trouble

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Oct 9, 2019 | 02:39 PM

tall freak

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From: Phoenix, AZ

79 emissions trouble

I didn't get through the 1140 pages of threads and the site search didn't help much, so apologies if I'm rehashing an old topic.

I just replaced the carb, timing gears and chain, water pump and fuel pump. After my second re-test I replaced the CAT, which didn't help at all (lesson learned, It's not the cat). Does anyone in the greater Phoenix metropolitan area know of any mechanics who still work on older vehicles. The shop I've been using for 15 years won't look at either of my old Fords anymore (79 Bronco, 84 F250). I've hit the limit on what I know to do, but I'm a dumb ol' electrician, not an auto mechanic. De-tuning just made the test readings worse. I pass the Idle Test, but blow out the Loaded test for both HC and CO. I hope there are still shops that work on these things. I love my Bronco...........

Jim

Oct 9, 2019 | 05:36 PM

85e150

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Is this thing a high mile oil burner?

Carb adjusted, no power valve issues, float level too high, choke adjusted?

Fuel pressure, needle and seat ok?

PCV working properly, not sucking oil?

Ignition components correct, timing right?

Does it miss under load?

Oct 9, 2019 | 07:11 PM

tall freak

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From: Phoenix, AZ

Thanks for the response. The fuel/air mix is good as far as I can tell. I couldn"t tell you about the choke. I set it up like the old setting and it runs and starts well. It's a new carb so I don't think its a float prob. I don't have the experience to know if I have the carb set up properly. This is my problem. I need an expert or at least someone who has experience. I replaced the timing chain and gears before I installed the carb. It was set right when I started it up, but had to de-tune it for my second retest. It got me closer, but not enough to pass emissions.

It's a frankentstein motor with serious bearing issues (Main and Rod bearings) and super high miles. I have a used motor that I bought to rebuild for the Bronco, but it has a lot of scale in the water jacket (overheating issues with original owner). I may have to pull it off the road to tackle that project. I would still like to have someone local to bail me out. Shadetree mechanic'n in the desert with no shade or tree is hard to motivate for.

Oct 9, 2019 | 11:07 PM

85e150

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Try asking if anyone knows a good wrench here:

https://www.ford-trucks.com/forums/forum80/

Oct 11, 2019 | 08:19 PM

bluovl

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From: SoCal

I love my old 78' Bronco also. Lets cut to the chase. My truck is a bone stock 78 with cat. It's a 351M with all the factory smog parts intact. Oh yes, it does have a complete MSD ignition system which is legal here in Cali. It passes smog every year without a problem. It failed the evap test once because of a leaky vacuum line to fuel tank. These engines had extremely low compression ratios, along with retarded timing they were able pass the smog test. Is your truck stock? If you've done anything to advance the timing or raise the CR it won't make it. Trust me I know and learned the hard way back in the 80'. My plan now is to pull the 351M and swap in a 2019 Coyote f150 4x4 motor and trans. There are kits available for the 4x4 dent side trucks now. Ok I don't know if I'm helping, but you've got to start with stock setup. BTW I thought AZ was a lot easier on these older vehicles. We get no love in Cali.

Oct 16, 2019 | 08:13 AM

tall freak

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From: Phoenix, AZ

Thanks for that info. Arizona adopted California standards for these older vehicles several years ago. I've been doing well since I did the carb and CAT in 2011, but I just put a new carb on it and it's giving me fits. I detuned it as I normally do, but this new carb still has me running high HC and CO at the loaded reading. It is a stock motor with plenty of miles. I think 85e150 has it right, that it's just old and time to die. it feels strong with no hesitation or stutter at any speed. but may be passing enough oil now to give me a bad burn. I'm pulling out the used spare M-Block and going to get it road ready. I'm still going to need a local wrench to help pass emissions when I do the swap to make sure. Twenty dollars for Test/Retest is getting expensive after my second cycle.

Thanks for the response and thanks to 85e150 for the pointer. I forgot about the SW Chapter and AZ club section.

Oct 16, 2019 | 05:41 PM

Tedster9

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From: Waterloo, Iowa

Have you performed a compression test? Carburetor has been replaced, though what was on there? What did you replace it with?

New timing set, means valve timing has changed, maybe for the better, though maybe not. On the assumption that compression is acceptable then might look into a wideband O2 sensor, they will help dial a carburetor in real good. Like you say, then might have to detune it to get it to pass.