Background - the truck is an 85 F150 with the 300 I6. The truck has 137300 miles and the engine was rebuilt at about 100000 miles in 2008. The truck sat unused from June 2009 until November 2011 when I started working on it to get it back on the road. During the various test drives I've logged about 100 miles and the truck runs great other than failing the emissions test.

Problem - The truck has failed the emissions test twice. The first test failed the fuel evap test and the NO emissions at 15 & 25 mph were too high. For the second test the fuel evap system was fine but the HC emissions at 15mph and the NO emissions at 15 & 25 mph are too high. I can post the test results if needed. I have since learned that when the truck was last tested for emissions in 2008, after the engine was rebuilt, the truck failed and the mechanic dad used had a friend "make it pass" rather than figure out what was wrong.

Repairs made - Prior to the first emissions test in March the carburetor was rebuilt, spark plugs and wires replaced, the radiator removed and cleaned and the gasket replaced for the inlet end tank (it started leaking so that's why I took it apart), and the pre-carb heater hose replaced because it was missing. The truck was tested and failed for the first time at this point. For the too high NO numbers I replaced the EGR valve as it looked original and looked terrible. I found and repaired a leak in the fuel line beneath where the driver sits. I also traced and replaced all of the rubber hoses in the fuel evap system including dropping the gas tank and replacing those evap hoses. Many of them were bad. I replaced a bad o-ring in the charcoal canister and I replaced the pcv valve for no particular reason other than it was cheap and attached to the evap hoses. After this the truck was tested for the second time and failed again as described above.

Solution - that's what I want to know. Any ideas?

My thoughts - If I understand the fuel evap system correctly, I suspect fixing those evap leaks is what caused the increase in emissions in the second emissions test since that introduced additional fuel vapor into the system for the second test. Just a guess. Additionally, I know that after dad parked the truck he would start it from time to time (before he and the truck moved in with me) and at some point it started blowing black smoke out the tailpipe. Dad does not remember how long or how many times the truck was allowed to idle while it was smoking. I also know the catalytic converters (there are two in total) are original and probably in need of replacement. I imagine the black smoke probably gummed up a few things including the cat, but I'd rather be sure before replacing something that pricey. Otherwise, the only thing I can imagine doing that may prove helpful would be to remove and clean the intake manifold.

Any ideas what do to next?

 

Wow... You have the worst possible scenario - a 1985 I6 with the feedback carburetor + California emissions - at least, this is what it looks like so far.

We have some people here who are pretty good with that setup, though.

The EVAP system collects vapors from the gas tank & carb and stores them in a charcoal canister for later induction into the combustion chamber. I don't see how this can be causing your problem.

Black smoke is too much gas.

First thing I would do is ask the computer what it thinks is happening; here's how to do it at home:

Fuel Injection Technical Library » How To Run a Self-Test
Ford Ranger/Bronco II EEC-IV Testing

 

First thing I would look at is your Manifold Absolute Pressure sensor (MAP) it's located on the right inner fender near the starter relay. It should have full manifold vacuum on it. If not, fix this first! Check and make sure the carburetor isn't loose at the throttle body to float bowl joint. Check your emission label (either on the valve cover or the radiator upper panel) for idle mixture adjustment procedure and see if it adjusts.

 

How high are your HC and NO numbers? If they haven't given you the scarlet letter of "gross polluter" than were not that far off. EVAP will have nothing to do with that, the peoples republic of southern California believes that evaporating gasoline is a pollutant and treated in another manner, they will even pressurize your gas tank to test for this. Have you tested it since replacing the EGR? Is there still black smoke? A running rich condition, would give you black smoke and high CO readings additionally the smog tech should fail it for visually smoking out the tailpipe. Usually EGR failures will throw your readings in to thousands of parts per million over. The Catalytic converters also help elieviate NO emissions, so if your EGR is new and working and your NO is a few hundred off and HC isn't more than 1000 off, than more than likely its the cats. Getting cats replaced here can be difficult, because technically per the law they have to be a bolt in setup, no universal weld ins unless they have a CARB EO number, which isn't always easy to find. On the bright side, it says you're in Tustin, so not far from Santa Ana where you would have an easy time getting the cats replaced, decades ago there was a Mexican place there called Plaza Muffler that might be able to get you the cats. Unless you've still got smoke, I'd say the carb is ok, because running rich conditions cause lower exhaust gas temperatures and less NO emissions.

 

I know it can be expensive, but a new catalytic converter will bring those numbers way down. If the truck was running high HC and NO before, that buildup in the CAT could saturate the core and effectively render it useless. I don't know what it costs in CA for emissions testing, but you could try some jy swaps. Anything in the JY is a gamble. A new CAT should cost about 300 installed, less if you can weld it yourself. New CAT and new Carb is what it took for my '79 Bronco......

Jim

 

Before the first test, the spark plugs and wires were replaced and the carb was rebuilt. Rebuilding the carb eliminated the smoking and now it does not smoke at all. It starts easily and runs well. Here are those numbers:

Fuel evap test - failed

<TABLE style="WIDTH: 528pt; BORDER-COLLAPSE: collapse" border=0 cellSpacing=0 cellPadding=0 width=704><COLGROUP><COL style="WIDTH: 48pt" span=4 width=64><COL style="WIDTH: 48pt" span=2 width=64><COL style="WIDTH: 48pt" span=5 width=64><TBODY><TR style="HEIGHT: 15pt" height=20><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; WIDTH: 48pt; HEIGHT: 15pt; BORDER-TOP: #ece9d8; BORDER-RIGHT: windowtext 0.5pt solid" class=xl65 height=20 width=64>Speed</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; WIDTH: 48pt; BORDER-TOP: #ece9d8; BORDER-RIGHT: windowtext 0.5pt solid" class=xl65 width=64>Speed</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; WIDTH: 48pt; BORDER-TOP: #ece9d8; BORDER-RIGHT: #ece9d8" class=xl63 width=64>HC</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; WIDTH: 48pt; BORDER-TOP: #ece9d8; BORDER-RIGHT: #ece9d8" class=xl63 width=64>HC</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; WIDTH: 48pt; BORDER-TOP: #ece9d8; BORDER-RIGHT: windowtext 0.5pt solid" class=xl65 width=64>HC</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; WIDTH: 48pt; BORDER-TOP: #ece9d8; BORDER-RIGHT: #ece9d8" class=xl63 width=64>CO</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; WIDTH: 48pt; BORDER-TOP: #ece9d8; BORDER-RIGHT: #ece9d8" class=xl63 width=64>CO</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; WIDTH: 48pt; BORDER-TOP: #ece9d8; BORDER-RIGHT: windowtext 0.5pt solid" class=xl65 width=64>CO</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; WIDTH: 48pt; BORDER-TOP: #ece9d8; BORDER-RIGHT: #ece9d8" class=xl63 width=64>NO</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; WIDTH: 48pt; BORDER-TOP: #ece9d8; BORDER-RIGHT: #ece9d8" class=xl63 width=64>NO</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; WIDTH: 48pt; BORDER-TOP: #ece9d8; BORDER-RIGHT: #ece9d8" class=xl63 width=64>NO</TD></TR><TR style="HEIGHT: 15pt" height=20><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; HEIGHT: 15pt; BORDER-TOP: #ece9d8; BORDER-RIGHT: windowtext 0.5pt solid" class=xl65 height=20>MPH</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; BORDER-TOP: #ece9d8; BORDER-RIGHT: windowtext 0.5pt solid" class=xl65>RPM</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; BORDER-TOP: #ece9d8; BORDER-RIGHT: #ece9d8" class=xl63>Max</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; BORDER-TOP: #ece9d8; BORDER-RIGHT: #ece9d8" class=xl63>Ave</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; BORDER-TOP: #ece9d8; BORDER-RIGHT: windowtext 0.5pt solid" class=xl65>Meas</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; BORDER-TOP: #ece9d8; BORDER-RIGHT: #ece9d8" class=xl63>Max</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; BORDER-TOP: #ece9d8; BORDER-RIGHT: #ece9d8" class=xl63>Ave</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; BORDER-TOP: #ece9d8; BORDER-RIGHT: windowtext 0.5pt solid" class=xl65>Meas</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; BORDER-TOP: #ece9d8; BORDER-RIGHT: #ece9d8" class=xl63>Max</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; BORDER-TOP: #ece9d8; BORDER-RIGHT: #ece9d8" class=xl63>Ave</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; BORDER-TOP: #ece9d8; BORDER-RIGHT: #ece9d8" class=xl63>Meas</TD></TR><TR style="HEIGHT: 15pt" height=20><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; HEIGHT: 15pt; BORDER-TOP: #ece9d8; BORDER-RIGHT: windowtext 0.5pt solid" class=xl65 height=20>15</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; BORDER-TOP: #ece9d8; BORDER-RIGHT: windowtext 0.5pt solid" class=xl65>1981</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; BORDER-TOP: #ece9d8; BORDER-RIGHT: #ece9d8" class=xl63>92</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; BORDER-TOP: #ece9d8; BORDER-RIGHT: #ece9d8" class=xl63>61</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; BORDER-TOP: #ece9d8; BORDER-RIGHT: windowtext 0.5pt solid" class=xl65>58</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; BORDER-TOP: #ece9d8; BORDER-RIGHT: #ece9d8" class=xl63>0.61</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; BORDER-TOP: #ece9d8; BORDER-RIGHT: #ece9d8" class=xl63>0.08</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; BORDER-TOP: #ece9d8; BORDER-RIGHT: windowtext 0.5pt solid" class=xl65>0.05</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; BORDER-TOP: #ece9d8; BORDER-RIGHT: #ece9d8" class=xl63>760</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; BORDER-TOP: #ece9d8; BORDER-RIGHT: #ece9d8" class=xl63>365</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; BORDER-TOP: #ece9d8; BORDER-RIGHT: #ece9d8" class=xl64>1086</TD></TR><TR style="HEIGHT: 15pt" height=20><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; HEIGHT: 15pt; BORDER-TOP: #ece9d8; BORDER-RIGHT: windowtext 0.5pt solid" class=xl65 height=20>25</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; BORDER-TOP: #ece9d8; BORDER-RIGHT: windowtext 0.5pt solid" class=xl65>1893</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; BORDER-TOP: #ece9d8; BORDER-RIGHT: #ece9d8" class=xl63>79</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; BORDER-TOP: #ece9d8; BORDER-RIGHT: #ece9d8" class=xl63>46</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; BORDER-TOP: #ece9d8; BORDER-RIGHT: windowtext 0.5pt solid" class=xl65>50</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; BORDER-TOP: #ece9d8; BORDER-RIGHT: #ece9d8" class=xl63>0.77</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; BORDER-TOP: #ece9d8; BORDER-RIGHT: #ece9d8" class=xl63>0.1</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; BORDER-TOP: #ece9d8; BORDER-RIGHT: windowtext 0.5pt solid" class=xl65>0.03</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; BORDER-TOP: #ece9d8; BORDER-RIGHT: #ece9d8" class=xl63>784</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; BORDER-TOP: #ece9d8; BORDER-RIGHT: #ece9d8" class=xl63>365</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; BORDER-TOP: #ece9d8; BORDER-RIGHT: #ece9d8" class=xl64>960</TD></TR></TBODY></TABLE>

Here I failed only the NO test and the fuel evap test.

So I replaced the EGR valve, located and fixed a tear in the fuel line (which i found looking for the evap leak) and I fixed the evap leak by tracing and replacing the all of the evap hoses including dropping the gas tank and replacing the evap hose there too. They were all in bad shape. I also changed the oil and ran some Lucas Oil fuel system cleaner through it. It ran even better and still no smoking.

I then ran it through the emissions test for the second time. Here are those numbers:

Fuel evap test - passed

<TABLE style="WIDTH: 528pt; BORDER-COLLAPSE: collapse" border=0 cellSpacing=0 cellPadding=0 width=704><COLGROUP><COL style="WIDTH: 48pt" span=4 width=64><COL style="WIDTH: 48pt" span=2 width=64><COL style="WIDTH: 48pt" span=5 width=64><TBODY><TR style="HEIGHT: 15pt" height=20><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; WIDTH: 48pt; HEIGHT: 15pt; BORDER-TOP: #ece9d8; BORDER-RIGHT: windowtext 0.5pt solid" class=xl67 height=20 width=64>Speed</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; WIDTH: 48pt; BORDER-TOP: #ece9d8; BORDER-RIGHT: windowtext 0.5pt solid" class=xl67 width=64>Speed</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; WIDTH: 48pt; BORDER-TOP: #ece9d8; BORDER-RIGHT: #ece9d8" class=xl65 width=64>HC</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; WIDTH: 48pt; BORDER-TOP: #ece9d8; BORDER-RIGHT: #ece9d8" class=xl65 width=64>HC</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; WIDTH: 48pt; BORDER-TOP: #ece9d8; BORDER-RIGHT: windowtext 0.5pt solid" class=xl67 width=64>HC</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; WIDTH: 48pt; BORDER-TOP: #ece9d8; BORDER-RIGHT: #ece9d8" class=xl65 width=64>CO</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; WIDTH: 48pt; BORDER-TOP: #ece9d8; BORDER-RIGHT: #ece9d8" class=xl65 width=64>CO</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; WIDTH: 48pt; BORDER-TOP: #ece9d8; BORDER-RIGHT: windowtext 0.5pt solid" class=xl67 width=64>CO</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; WIDTH: 48pt; BORDER-TOP: #ece9d8; BORDER-RIGHT: #ece9d8" class=xl65 width=64>NO</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; WIDTH: 48pt; BORDER-TOP: #ece9d8; BORDER-RIGHT: #ece9d8" class=xl65 width=64>NO</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; WIDTH: 48pt; BORDER-TOP: #ece9d8; BORDER-RIGHT: #ece9d8" class=xl65 width=64>NO</TD></TR><TR style="HEIGHT: 15pt" height=20><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; HEIGHT: 15pt; BORDER-TOP: #ece9d8; BORDER-RIGHT: windowtext 0.5pt solid" class=xl67 height=20>MPH</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; BORDER-TOP: #ece9d8; BORDER-RIGHT: windowtext 0.5pt solid" class=xl67>RPM</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; BORDER-TOP: #ece9d8; BORDER-RIGHT: #ece9d8" class=xl65>Max</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; BORDER-TOP: #ece9d8; BORDER-RIGHT: #ece9d8" class=xl65>Ave</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; BORDER-TOP: #ece9d8; BORDER-RIGHT: windowtext 0.5pt solid" class=xl67>Meas</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; BORDER-TOP: #ece9d8; BORDER-RIGHT: #ece9d8" class=xl65>Max</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; BORDER-TOP: #ece9d8; BORDER-RIGHT: #ece9d8" class=xl65>Ave</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; BORDER-TOP: #ece9d8; BORDER-RIGHT: windowtext 0.5pt solid" class=xl67>Meas</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; BORDER-TOP: #ece9d8; BORDER-RIGHT: #ece9d8" class=xl65>Max</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; BORDER-TOP: #ece9d8; BORDER-RIGHT: #ece9d8" class=xl65>Ave</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; BORDER-TOP: #ece9d8; BORDER-RIGHT: #ece9d8" class=xl65>Meas</TD></TR><TR style="HEIGHT: 15pt" height=20><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; HEIGHT: 15pt; BORDER-TOP: #ece9d8; BORDER-RIGHT: windowtext 0.5pt solid" class=xl67 height=20>15</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; BORDER-TOP: #ece9d8; BORDER-RIGHT: windowtext 0.5pt solid" class=xl67>1213</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; BORDER-TOP: #ece9d8; BORDER-RIGHT: #ece9d8" class=xl65>92</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; BORDER-TOP: #ece9d8; BORDER-RIGHT: #ece9d8" class=xl65>61</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; BORDER-TOP: #ece9d8; BORDER-RIGHT: windowtext 0.5pt solid" class=xl68>133</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; BORDER-TOP: #ece9d8; BORDER-RIGHT: #ece9d8" class=xl65>0.61</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; BORDER-TOP: #ece9d8; BORDER-RIGHT: #ece9d8" class=xl65>0.08</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; BORDER-TOP: #ece9d8; BORDER-RIGHT: windowtext 0.5pt solid" class=xl67>0.21</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; BORDER-TOP: #ece9d8; BORDER-RIGHT: #ece9d8" class=xl65>760</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; BORDER-TOP: #ece9d8; BORDER-RIGHT: #ece9d8" class=xl65>365</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; BORDER-TOP: #ece9d8; BORDER-RIGHT: #ece9d8" class=xl66>1838</TD></TR><TR style="HEIGHT: 15pt" height=20><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; HEIGHT: 15pt; BORDER-TOP: #ece9d8; BORDER-RIGHT: windowtext 0.5pt solid" class=xl67 height=20>25</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; BORDER-TOP: #ece9d8; BORDER-RIGHT: windowtext 0.5pt solid" class=xl67>1906</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; BORDER-TOP: #ece9d8; BORDER-RIGHT: #ece9d8" class=xl65>79</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; BORDER-TOP: #ece9d8; BORDER-RIGHT: #ece9d8" class=xl65>46</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; BORDER-TOP: #ece9d8; BORDER-RIGHT: windowtext 0.5pt solid" class=xl67>58</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; BORDER-TOP: #ece9d8; BORDER-RIGHT: #ece9d8" class=xl65>0.77</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; BORDER-TOP: #ece9d8; BORDER-RIGHT: #ece9d8" class=xl65>0.1</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; BORDER-TOP: #ece9d8; BORDER-RIGHT: windowtext 0.5pt solid" class=xl67>0.03</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; BORDER-TOP: #ece9d8; BORDER-RIGHT: #ece9d8" class=xl65>784</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; BORDER-TOP: #ece9d8; BORDER-RIGHT: #ece9d8" class=xl65>365</TD><TD style="BORDER-BOTTOM: #ece9d8; BORDER-LEFT: #ece9d8; BACKGROUND-COLOR: transparent; BORDER-TOP: #ece9d8; BORDER-RIGHT: #ece9d8" class=xl66>1007</TD></TR></TBODY></TABLE>
Now I failed the HC emissions at 15 mph as well as the NO emissions at 15 & 25 mph. Upon typing this, I realized that all of the emissions have increased at 15 mph and the rpm's at 15 mph changed from 1981 for the first test to 1213 for the second test. I don't know if this is important, but I find it to be a curious coinsidence at least.

From crawling around beneath the truck I can see the cats are original based on the ford part numbers I see. The truck also has two cats. My guess (just a guess) is that the first (front) cat does most of the work and the second (rear) cat bats clean up, as it were. When I called the local muffler shop they told me the first cat is more expensive than the second.

 

I imagine that between age, Dad running it while it was smoking for some unknown amount of time and the increased emissions while he ran it after the mechanic allegedly "fixed" the last emissions test (meaning the mechanic had the test fixed, as he and the smog test place were buddies, rather than fix the actual problem) that the cat is probably toast. I am convinced the cat has to be replaced. My hope is that replacing the front cat (I presume it does the mot work, but just a guess) will do the trick.

 

If you have black smoke coming out the back, it needs more than a catalytic converter.................

There are tests that can be performed, one using air pressure, to determine if a cat is in need of replacing or not. Verify it needs one before spending hundreds of dollars because you think it "should" be the problem....

 

There is no smoke. That was resolved with the carb rebuild. I was not aware of a test for the cat. Is this a test that can be done a home or must a shop perform this test?

 

Catalysts Don't have to be more restrictive to go bad, and honestly by the book, back pressure greater than 3-5 pounds is considered excessive. Essentially, because of natural erosion, they can wear out and have less material, contaminates from when it did run with smoke can contaminate the substrate as well. Now I'm a little concerned about the rpm change, is your truck manual or auto, and which one? With the revs in the 1800-1900 range, the NO was only 3-4 hundred off, in the 1200 range, way off, forget about it. Was your truck warmed all the way up, the gauge around half way or so? Have you checked your vacuum line routing for the egr valve? It seems like its opening, but either not enough or not enough flow is going through. Before you spend the big bucks on the cats, lets verify that the egr system is hooked up and in good order, vacuum lines routed properly and in good shape, if there is a thermal valve, make sure it does its job, if there's a reference vacuum line to the carb, make sure vacuum volume increases with engine speed. Better yet, if you still have the VECI label under the hood, with vacuum routing, take a pic of it, lets make sure I don't leave any stones unturned.

 

I know, I'm just trying to encourage the guy to do some diagnostic work and replace things only that have proven to be bad, not based on conjecture.

BTW I learned 5 PSI is the upper limit, 3 PSI would be approaching that but doesn't yet necessarily warrant replacement (but each situation is different).

In any event, there have been some good posts made here but one thing still gnaws at me....

This is a computer-controlled engine, the computer enrichens/leans the mixture based on what it thinks is happening.To me, that's a great place to start with a situation like this.

Some cat tests require specialized tools, using just a vacuum gauge can sometimes give indications as can temperature (measured with one of those handheld infrared things that can be gotten from Harbor Freight). Go Googling around on that one....

 

I have not yet checked the computer for codes. That is the next thing I'm going to do before money is spent.

 

Most folks say no way when I say really 1psi is max, its just kind of grown to be an unofficial 3-5. When one comes in and we believe it to be plugged, it usually pegs well over 30 and off the gauge. Also outlet temperature sure be at least 150 degrees Fahrenheit higher on the output vs. input. seeing as CO is not off the charts mixture is fine, also, if mixture is rich NO will go almost away. Was hoping to see some pics, sounds like the person who "made it pass" may have rerouted things.

 

More like they looked the other way and made the sure the results were good without messing with or even necessarily testing the truck itself. Mechanic's fault for cheating and taking the easy way out. I've in the last year or two of a couple instances wherein he cut corners on vehicles.

 

How through is the place that's doing the smog on the truck? slightly advanced timing will give you those type of numbers as well, they're supposed to verify its set right or fail it, but so many people that do this are so young and don't know what a carb is or an air pump, or why or how one would adjust timing.