First Time Emission Failure?????
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First Time Emission Failure?????
This is a 1992 Ford Bronco with 351, auto trans, and 71K miles. I has previously always easily passed the Nevada emission test. Yesterday I had it emission tested and it flunked at all rpms with high CO and HC. The "Check Engine Light" has never came on once. It has not yet had a diagnostic test.
-Do you think this is the failure of the ECU/ECC/ECM?
-If so, is this common after a few years?
-Any good sources for new/used ones?
Thanks.
Marty
-Do you think this is the failure of the ECU/ECC/ECM?
-If so, is this common after a few years?
-Any good sources for new/used ones?
Thanks.
Marty
Posting Guru
Joined: Apr 2005
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From: Longview, TX
Have you pulled the codes? It can be done with a paper clip and counting engine light flashes. I prefer the digital code reader found at most places for thirty something dollars and routinely use it when I change the oil. Sometimes codes are available even though there has never been a check engine light. Try the Forums then Search above for more info.
Senior User
Joined: Sep 2006
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My F150 5.0L with 182,000 miles just had the emissions test, passed with flying colors (i had no codes though so i would check them first) I ran the tank down to 1/4 tank then dumped 2 bottles of Iso-Heet into the tank (the red bottle) it is gas line anti-freeze but its pure isoporpyl alcohol. I was well under the limits.
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Joined: Feb 2007
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From: Chicagoland
Originally Posted by martycj8
high CO and HC.
Calvin
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The Thermactor pipe appears to be in good condition and enters the exhaust pipe just downstream of the CAT. The Thermactor system hoses/pipes appear to be ok from the airpump to the air control valve and air check valve. It is very tight working in the air control valve area. I guess it is time for a diagnostic scan. Thanks for your replys.
Marty
Marty
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From: Coweta,GA, GO DAWGS!!!!!!
You need someone with a "good" scan tool..........like a snap-on modis or so.
What you need to know is if the o2 sensor is switching or not. I just went through this with my 91 f-150. She never threw a code and ran great, but it failed emissions twice. I took it to a friend of mine and we watched the enigne parameters for a good while(with it at op. temp.)
The problem-the o2 sensor was working but it wasn't switching to the high side of the output parameters.
This caused the engine to inject too much fuel at higher rpm's and speeds. At test times what I failed on was high hc's and high co's. You need to smell the exaust at the exit and see if it smells heavy of gas. If it does, i'd start with diagnosing the o2.
Other things I wondered about as I was trying to pin-point the problem-
A leaky injector
bad plug/plugs or wire/wires
last resort- bad ecu, I had to rule that one out since mine was new, I triple checked the part # to make sure.
What you need to know is if the o2 sensor is switching or not. I just went through this with my 91 f-150. She never threw a code and ran great, but it failed emissions twice. I took it to a friend of mine and we watched the enigne parameters for a good while(with it at op. temp.)
The problem-the o2 sensor was working but it wasn't switching to the high side of the output parameters.
This caused the engine to inject too much fuel at higher rpm's and speeds. At test times what I failed on was high hc's and high co's. You need to smell the exaust at the exit and see if it smells heavy of gas. If it does, i'd start with diagnosing the o2.
Other things I wondered about as I was trying to pin-point the problem-
A leaky injector
bad plug/plugs or wire/wires
last resort- bad ecu, I had to rule that one out since mine was new, I triple checked the part # to make sure.
Fleet Mechanic
Joined: Mar 2005
Posts: 1,603
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From: St Louis
Dont discount the cat as being good with only 71k on it. High hydro carbons and high Nitrous oxides mean that some portion of the emisions is not working. The easy way to tell if the cat has quit is basically to feel if it is getting much warmer than the rest of the exhaust. Or find someone with an infared thermometer to see if the cat is heating up. If the rest of the system is good then the cat is probably your problem. It doesnt take much to cut the cat off and replace it. I would measure your pipe though and get the right size inlet and outlet to fit your exhaust.
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The problem ended up being the Fuel Pressure Regulator 4764. It was creating 80PSI where 35-40PSI is the norm. Fuel was dumping through. I always thought that lower pressure was more common. Why didn't I just look at the fuel pressure myself? Thanks for your replies.
Marty
Marty
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