Failed Emissions, Help! (long)
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Elder User
Joined: Mar 2003
Posts: 788
Likes: 1
From: Hendersonville, TN
Failed Emissions, Help! (long)
After weeks of sitting, I got my clutch installed in my 94 300-I6 F150, and started driving
it again. It ran OK for a few days, but while helping my sister-in-law move Saturday it developed
a miss, which worsened over the next few days to the point that it was nearly undriveable and
would shake violently when lugged. Yesterday I pulled the plugs and found #'s 1 & 3 caked with
brown crud like additive stuff you see in the plug guides. #2 was oil/carbon-fouled. It wasn't real
wet, but had black funk completely filling the gap. I pulled a compression test and all six cyls
read 160-175 PSI, with #2 being one of the best.(Oil coming through guides?) Anyway, new plugs
and it ran like a top. Ran through emissions test today 'cause plates are expired--gotta get
it done! It failed, first time ever, with high HC readings. (384, max is 220 -- always has
been around 150). CO and CO2 were well within limits. No perceptible exhaust smoke of any
color, doesn't smell rich, but inside of tailpipe looks a little black/sooty. In addition to
the plugs it has a recent cap & rotor, wires are a little old but appear sound. Currently no
miss/running great, and getting excellent mileage(thank goodness, with these prices!). I did
find one thing that I'd posted here before about, and didn't find an answer, and had forgotten:
There's a vacuum line attached to a valve on the top of the air pump that goes nowhere. I can't
find a port to attach it too, and looking at the Haynes manual, I assume it should be hooked
to one of the valves on the valve cover, but find no port there for it either. Questions:
1. Anyone know about this vacuum line? 2. Will that cause high HC(no air going into exhaust/
converter, maybe?). 3. Any other obvious problem areas that might cause this?
BTW, there are no codes in the computer, and the testing station is right off the main highway.
I ran it through hot, fresh off the main road after about 30 miles of mostly interstate driving.
Engine is all-original 215K miles, as is all emissions equip. including the O2 sensor and
the converters. Any help much appreciated, as I need to get this done before I get a ticket
for expired tags.
it again. It ran OK for a few days, but while helping my sister-in-law move Saturday it developed
a miss, which worsened over the next few days to the point that it was nearly undriveable and
would shake violently when lugged. Yesterday I pulled the plugs and found #'s 1 & 3 caked with
brown crud like additive stuff you see in the plug guides. #2 was oil/carbon-fouled. It wasn't real
wet, but had black funk completely filling the gap. I pulled a compression test and all six cyls
read 160-175 PSI, with #2 being one of the best.(Oil coming through guides?) Anyway, new plugs
and it ran like a top. Ran through emissions test today 'cause plates are expired--gotta get
it done! It failed, first time ever, with high HC readings. (384, max is 220 -- always has
been around 150). CO and CO2 were well within limits. No perceptible exhaust smoke of any
color, doesn't smell rich, but inside of tailpipe looks a little black/sooty. In addition to
the plugs it has a recent cap & rotor, wires are a little old but appear sound. Currently no
miss/running great, and getting excellent mileage(thank goodness, with these prices!). I did
find one thing that I'd posted here before about, and didn't find an answer, and had forgotten:
There's a vacuum line attached to a valve on the top of the air pump that goes nowhere. I can't
find a port to attach it too, and looking at the Haynes manual, I assume it should be hooked
to one of the valves on the valve cover, but find no port there for it either. Questions:
1. Anyone know about this vacuum line? 2. Will that cause high HC(no air going into exhaust/
converter, maybe?). 3. Any other obvious problem areas that might cause this?
BTW, there are no codes in the computer, and the testing station is right off the main highway.
I ran it through hot, fresh off the main road after about 30 miles of mostly interstate driving.
Engine is all-original 215K miles, as is all emissions equip. including the O2 sensor and
the converters. Any help much appreciated, as I need to get this done before I get a ticket
for expired tags.
Senior User
Joined: Dec 2003
Posts: 215
Likes: 0
I'd test the wires. Remove one, measure it, and then check it's resistance with a multi-meter. If it's more than 5K ohms per foot, replace them. Check your coil wire also. If they pass, I'd check spark voltage (the testers are about $7 at most parts stores) against what the manual says (I don't have mine handy and it's a Haynes anyway). I'll take a look at my '92 and see where that line goes. And change out that poor oxygen sensor - it's surely doing nothing by now.
