High Hydrocarbons Help
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Tuned
Joined: Jul 2004
Posts: 476
Likes: 5
From: Delaware
High Hydrocarbons Help
Trying to help a friend with his 1988 F150 with 4.9 (300CI) six cylinder. He has failed our emmision test several times due to high hyrocarbons. Max allowed is 220 and his has been anywhere from 415 up to about 600. The truck has high miles but runs good and doesn't seem to smoke. He has changed spark plugs, cap, rotor, air filter, pcv. Put in new thermostat to get the temperature up correctly. I had him pull the pcv out previously to cut down the hydrocarbons being recirculated back thru the intake and that helped but he still failed. Nothing seems to work. Today I set the timing to 10BTDC as it was severely retarded and sent him back. The hydrocarbon level actually increased so he failed again. With our test it is tailpipe only so they don't look under the hood. Any suggestions? O2 sensor, EGR, Catalytic converter?
Senior User
Joined: Jul 2004
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From: N. Gwinnett
If it was smoking, I'd suggest changing to synthetic oil - I used Mobil 1. My former car (this was a 4.6, not a 4.9, 175k mi) JUST passed at 220 ppm. The smoking got worse. With synthetic, it tested at 45 ppm. The smoke wasn't particularly visible at idle, just on acceleration if you looked carefully in the mirror.
I can't remember the details for that year, but since you mention it, I would look at the oxygen sensor voltage pattern. When mine went bad it went from a regular peak-valley pattern, to something that looked like a drunk scrawling his name.
I learned too late that you can check cats with an infrared thermometer.
Hope this helps-
I can't remember the details for that year, but since you mention it, I would look at the oxygen sensor voltage pattern. When mine went bad it went from a regular peak-valley pattern, to something that looked like a drunk scrawling his name.
I learned too late that you can check cats with an infrared thermometer.
Hope this helps-
Senior User
Joined: Jul 2004
Posts: 124
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From: N. Gwinnett
Hate to say it, but I cheated (this was on the '97) I have an AutoTap scanner that plugs into an old laptop that can show me the wave form. I haven't had to do it on a non-OBDII system yet.
Here's a couple of articles that'll help:
Goto www.carleysoftware.com. Click on the button, "Tech Library free online repair articles" Scroll down to "Engine Performance and Emissions articles". Read these articles:
"Fixing Emissions Failures"
"Basic Emission Control Systems Overview"
"Understanding Oxygen Sensors"
"Troubleshooting with Temperature"
The first one will help you narrow it down & the others will help from there on out.
Keep us posted-
Here's a couple of articles that'll help:
Goto www.carleysoftware.com. Click on the button, "Tech Library free online repair articles" Scroll down to "Engine Performance and Emissions articles". Read these articles:
"Fixing Emissions Failures"
"Basic Emission Control Systems Overview"
"Understanding Oxygen Sensors"
"Troubleshooting with Temperature"
The first one will help you narrow it down & the others will help from there on out.
Keep us posted-
Senior User
Joined: Jul 2004
Posts: 124
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From: N. Gwinnett
Some of the auto parts chains can do this for you.
Don't let the word "oscilloscope" scare you. Some of the mid-range Fluke (electrical test) meters can display frequency like this. They make several automotive ones, and there are cheaper knockoffs.
Don't let the word "oscilloscope" scare you. Some of the mid-range Fluke (electrical test) meters can display frequency like this. They make several automotive ones, and there are cheaper knockoffs.
New User
Joined: Nov 2004
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I'm the original owner of a blue '82 f150 with 223K on my six. I had this same high hydrocarbon problem myself. We (that's me and the state emissions tech) finally re-jetted my Carter YF1 and that got problem solved. We went down 3 sizes from stock, and drilled out the jet from there till it just passed. Engine still has plenty of go. I can't tell the difference in power or gas mileage, and its not runnin too lean. 6 years later I did put on a new cat, the original just died. Hope this helps.
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Tuned
Joined: Jul 2004
Posts: 476
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From: Delaware
UPDATE! We finally got the truck to pass. I changed the O2 sensor checked the timing again and it still failed. Hydrocarbon allowed 220 and the reading was still 415. Still not right. Then I found that when I removed the spout connector to the distributor the timing did not change. So, when I was setting the timing at 10 BTDC it was wrong as the distributor still acted as if the connector was in even with it out. Didn't notice the difference as I was shutting off the truck before and after the spout connector was removed or installed. I checked the connector with a meter and it has continuity. What would cause the timing to not change? Since I can't get it to change, any ideal of where to set the timing with a light? It seems to be about 15 degress off to make it run right. We just backed off the timing about 15 degress and it went right thru with a reading of 111.
