I can't pass smog... Help!!
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Freshman User
Joined: Nov 2003
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From: The ATL
I can't pass smog... Help!!
Hey guys,
I have a 95 F150 with a 4.9 and a 5 speed. I can't seem to get it to pass California smog, and I need a few suggestions. I just replaced the cap and rotor, the spark plugs and wires. I used Autolite wires and Autolite single platinum plugs. The cap and rotor were no-name pieces from AutoZone. The truck passed everything but HC (ppm) measurement. It shows the max reading to pass can be 86 at 15mph. My truck measured 145. At 25mph, the state max is 51. My truck measured 148. In all the other sections, my trucks numbers were way below max and even below the average. It was running 91 octane at the time, and the timing was set at 13 degrees BTDC. The smog tech said it could be anything from timing to catalytic converters, to bad spark plugs (which I doubt). The tuneup was performed about 5 days ago, and the truck runs really well. I just took a 300 mile trip and averaged 17 mpg pulling a small utility trailer. Any suggestions before I pay these guys $80 for a diagnosis? O2 sensor and cats are original, Just had a fresh fuel filter and tune up, maybe 500 miles ago. No Check Engine lights, no weird symptoms. Whattayathink?
Thanks in advanced.
T.J.
I have a 95 F150 with a 4.9 and a 5 speed. I can't seem to get it to pass California smog, and I need a few suggestions. I just replaced the cap and rotor, the spark plugs and wires. I used Autolite wires and Autolite single platinum plugs. The cap and rotor were no-name pieces from AutoZone. The truck passed everything but HC (ppm) measurement. It shows the max reading to pass can be 86 at 15mph. My truck measured 145. At 25mph, the state max is 51. My truck measured 148. In all the other sections, my trucks numbers were way below max and even below the average. It was running 91 octane at the time, and the timing was set at 13 degrees BTDC. The smog tech said it could be anything from timing to catalytic converters, to bad spark plugs (which I doubt). The tuneup was performed about 5 days ago, and the truck runs really well. I just took a 300 mile trip and averaged 17 mpg pulling a small utility trailer. Any suggestions before I pay these guys $80 for a diagnosis? O2 sensor and cats are original, Just had a fresh fuel filter and tune up, maybe 500 miles ago. No Check Engine lights, no weird symptoms. Whattayathink?
Thanks in advanced.
T.J.
Senior User
Joined: Nov 2003
Posts: 155
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From: El Paso Texas
Is it coming up to temperature? I've had vehicles fail smog before when the thermostat was stuck open, and the vehicle was never reaching proper operating temperature. It would stay in open loop and fail smog.
Start with the cheap and easy stuff.
Start with the cheap and easy stuff.
Laughing Gas
Joined: Mar 2003
Posts: 877
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From: Colorado, U.S.A!
Don't run high octane gas in an engine that isn't designed for it. That will run up your HC because the stuff doesn't burn fast enough in the lower compression engine, resulting in unburned hydrocarbons. It will also cause carbon deposits in the cylinders for the same reason.
A fresh oil change right before testing helps, too.
Couldn't hurt to pull the codes. You can have codes set even with no check engine light.
A fresh oil change right before testing helps, too.
Couldn't hurt to pull the codes. You can have codes set even with no check engine light.
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From: El Dorado Co., CA.
Originally Posted by c96drumm
A fresh oil change right before testing helps, too
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From: The ATL
Thanks for the responses guys, I have a few questions regarding the timing though. The emissions sticker under the hood says the timing isn't adjustable, that it's computer controlled. The truck has a traditional distributor so I'm a bit confused. I checked my Haynes manual just to be sure, and it says TFI-IV systems and Duraspark III setups have to set the crankshaft position to the PCM"s assumed crankshaft position, rather than to set actual timing. The process doesn't read to be to difficult, but how do I determine what I have? How do I tell if it's a Duraspark II or III or a TFI-IV? My tell-tale sticker doesn't mention.
I talked to the smog tech again, and he said there seems to be a miss somewhere. Now that he mentioned it, I guess I can feel a slight miss under steady throttle at about 40 mph. Really minor though. It runs smooth at idle, and nothing weird under hard acceleration. That could definitely cause high HC numbers with unburned fuel sneaking by the missed spark. Any ideas on how to diagnose/repair? I appreciate it!
Oh, the truck is a 95 CA truck, 4.9 manual trans, OBD I with 99,000 miles. Except basic tuneup stuff, everything is original.
T.J.
I talked to the smog tech again, and he said there seems to be a miss somewhere. Now that he mentioned it, I guess I can feel a slight miss under steady throttle at about 40 mph. Really minor though. It runs smooth at idle, and nothing weird under hard acceleration. That could definitely cause high HC numbers with unburned fuel sneaking by the missed spark. Any ideas on how to diagnose/repair? I appreciate it!
Oh, the truck is a 95 CA truck, 4.9 manual trans, OBD I with 99,000 miles. Except basic tuneup stuff, everything is original.
T.J.
New User
Joined: Feb 2004
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From: Moriarty, NM
A thousand dollars later I got a pass. My 88 F250 needed a new cat @ $450+, and after getting shuffled betwen the test only shop, and the smog shop I ended up at the referee station. They passed it first time. They also recommend I call BAR about the "shuffle". The smog diagnostic shop reset my timing to 7 degrees, trying to get it through.
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Joined: Mar 2004
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Check the emissions sticker under the hood for the proper timing setting. I think you will find it to be 10 degrees BTDC. I am not sure how to set the timing on your 95, but on my 88 4.9L, 5 speed I have to pull a jumper plug off a wire going to the distributer and loosen and turn the distributer. I just smogged mine today, I was worried, but it did pass.
Good Luck!!
Good Luck!!
