I took my truck in for a smog check back in November and it failed. I just rebuild the carb and fixed all the vac leaks.
I have new ignition rotor and cap and wires and plugs.(I just now checked the gap and adjusted from .038 to .044 after I got home from smog.)

The plugs seem a bit lean. 1 and 6 look better then the rest.

The smog guy said I have worse readings hydrocarbons then the last smog after I fixed the vac leaks and rebuilt the carb.

Need opinions on all this. 1st smog fail. (Old)
2nd smog fail (new) after vac leaks repair and carb rebuild.
#1
#2
#3
#4
#5
#6

 

Those are some strange looking electrodes...
Actually those plugs do look really lean the last one looks about perfect to me.

So the first time he said you had an intake leak? What was the beef with the ignition timing?

 

I thought the plug electrodes looked weird too.
The plugs are motorcraft platinum spark plugs.

The first time there were nipple caps that were cracked and sucking in air.

The idle was too high and he couldn't get the timing

 

A few things you could try......
-make sure your idle mix adj screw is in where it needs to be and pull the idle down
-make sure your engine is nice and hot when they test it
-clean sponge filter in air cleaner where valve cover gets air
-correct thermostat
-minimum oil level
-good pcv valve and lines

 

Sponge filter where?

The idle is fine now on the recent test.

 

I think he is saying the small breather filter for the intake side of your PCV system.
I'm not sure where it is in the I-6's teardrop shape filter housing.
If you find it saturated with excessive blow-by it could be contributing to your high HC levels.

The one dirty plug on the end may be rings or a broken/missing intake valve seal.
Hard to tell without a leakdown test.
You are sooo close to passing (4 ppm? )

Platinum is very expensive.
They make the tip of the electrode small because of that and it has a high enough melting point that it can survive.
​​​​​​​This is supposed to facilitate ionization, just like a lightning rod is pointy.

 

In my 1980, it's right where the breather hose from the valve cover meets the filter housing. Can't say whether it moved somewhere else for 1986.

Are platinum plugs known to work well in these trucks? I don't have to pass an emissions check here, but I still use the exact plug (BSF-42?) specified on my emissions label because that is what the truck was designed for. Platinum could well be better (I genuinely don't know), but if you're trying for original performance or regulatory compliance, it's hard to go wrong with original parts.

 

Yes, wherever the valve cover hose connects to the filter housing.
On my truck I would say at the 3:00 position looking from the grille, but idk 300/4.9's.
If this filter is saturated from excessive blow-by *and* some of that oil vapor is making it through the regular air filter, it *could* lead to elevated HC readings.

But engines wear. If the valve guides/stem seals are sloppy, the bores worn, or oil control rings no longer able to do their job then that is going to show up at the tail pipe.

Might compare previous tests to this one.
See if it just appears to be normal wear.

The fail test is obviously at part throttle.
Maybe leaning out the carburetor could help, but those plugs look very clean to me.

Lots of people say to use regular copper plugs in these trucks (and I DO use NGK copper plugs because of poor QC found in new Autolite, Champion, etc)
Platinum plugs have a place in newer engines where access is horrible and recommended change intervals are over 100k miles.

 

The difference in the one plug was the first thing I noticed. Actually, I think that tan color on that plug is what you should aim for, isn't it? I'm no expert on reading plugs, but what concerns me is when one plug looks noticeably different from the others. I'd suggest running a compression test to make sure you aren't dealing with an internal engine problem. Won't cost anything but your time. Also check for a leaking intake manifold gasket, as that could also affect just one cylinder. Most all other faults would affect all cylinders, not just one.


Also, please be aware that few of us are experts at dealing with emissions testing. Unless a person has experience with an exhaust analyzer, there aren't a lot of concrete answers we can offer. For example, somebody might say to make adjustment A, and that brings down the HC, but might also raise the CO. We can suggest some basic common-sense stuff, but we may be sadly lacking in the specifics.


What is the retest policy? Do you have to pay each time?


After the compression test, I'd suggest installing stock spark plugs, not the platinum ones you have. Exotic metal plugs are designed for modern engines which typically have much higher combustion temperatures. Just a hunch on my part, but they may not be as efficient as plain old stock plugs in this situation.

 

CO is just incomplete combustion/too rich.
it would be odd that the *end* cylinder is getting a rich mix.

A leak down would better tell what's going on there.

 

1985/86 F150/350 & Bronco 300 I-6:

This filter has nothing to do with the PCV system.

Corrugated paper hose (D4ZZ-9D667-A) routes from purge outlet valve on charcoal canister to 90 degree elbow (E5UZ-9E606-A 3/4" O.D.) on the side of the air cleaner that is retained by a metal clip (D1AZ-9E628-A).

The clip also retains the D1AZ-9D695-A (Motorcraft FA-88) crankcase ventilation filter. Its plastic housing is located inside the air cleaner, then its nipple pokes thru a hole in the air cleaner.

The foam filter (D1AZ-9D697-A / Motorcraft FA-105) either came with the housing or was available by itself.

EVERY 1971 and later FoMoCo vehicle with Evaporative Emission uses similar parts.

 

Update- I did a compression test and it looks good. Not much difference between the cylinders to be concerned I don't think.
I think I should get a new air cleaner filter since I have been using a k&n that came with the truck.
I will get some slandered plugs and put these away.
I also played with the mixture screw and it seems to be smoother running.
The pcv seems to be working fine and the lines are good and tight.
Don't know about the thermostat but the truck passed fine the last couple tests before with the current thermostat.
I don't get why the plug is running better then the rest but that is what I should be going for.
I do get 1 more test for free then I have to pay again.

I will get to more of your all posted info later with more time.

 

Just lean the carb down as much as you can before the test, make sure the engine is hot, and if you have to wait in line, keep the engine revved up to keep the temp up. And, I sure am glad I don't live in a state that smog checks a truck over 30 years old.

 

Just ordered a few parts. I'll post status after install.

 

Here's an emissions "readings" chart that may help you with your diagnosis.

High CO2 indicates good running engine (should be around 15%)
High O2 indicates running lean (should be less than 0.5%)
High HC indicates running rich (should be less than 10)
High CO indicates there is not enough air to support complete combustion (should be less than 0.1%)

** High CO and low O2 indicate running slightly rich (with high HC = incomplete combustion).
** Low CO and High O2 indicate running slightly lean (with high HC = incomplete combustion).