Failed Emissions
#1
Hi. I have a 96 f150 4x4 w/dual tanks & an inline 6 4.9 and I just failed emissions. And they gave me these 4 reasons. Im lost and if anyone can help i would love it. Reason 1. P0411 "SECONDARY AIR INJECTION SYSTEM INCORRECT FLOW DETECTED. Reason 2. P0401 EXHAUST GAS RECIRCULATION FLOW INSUFFICIENT DETECTED. Reason 3. P0171 SYSTEM TOO LEAN (BANK 1)(2). Reason 4. P0174 SYSTEM TOO LEAN (BANK 2).
Last edited by Dahnkey; 08-14-2013 at 03:40 PM.
#4
Senior Member
Just from personal experience I have seen the air pump under the hood disconnected or disabled. There should be a diagram near the radiator or on the hood that shows all the emission parts attached to the motor, if they have been disabled or removed it will cause the problems you are having.
#5
Just from personal experience I have seen the air pump under the hood disconnected or disabled. There should be a diagram near the radiator or on the hood that shows all the emission parts attached to the motor, if they have been disabled or removed it will cause the problems you are having.
#6
Senior Member
Not unless it's very dirty or he left a bunch of stuff disabled. You could need a good tune-up, there are a lot of things than can cause these type of failures. I'm not a code chaser so one of the other guys can help you thru getting those corrected if everything else looks good. If the previous owner disabled the system, and you are not mechanically, you might want to get it into a shop for an estimate. Post a picture of the engine compartment so we can see what is hooked up.
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#8
He's running lean, which rules out clogged air filter. Shut off air, runs RICH, not lean.
EGR valves are known to get stuck, due to the crap sucked into them out of the exhaust gas stream. It might need to be replaced.
Auxiliary air is pumped into the exhaust gas stream to help burn unburned hydrocarbons. The so-called "smog-pump". Air pumps wear out and lose efficiency, (if not disconnected, check hoses). It may need to be replaced, too.
The entire engine running lean could be caused simply by a partly clogged fuel filter. Check fuel pressure, under load if possible. If it's low even at idle, replace the filter. Other causes for lean running, oxygen sensors, would be picked up by the computer and called out trouble codes of their own. imp
EGR valves are known to get stuck, due to the crap sucked into them out of the exhaust gas stream. It might need to be replaced.
Auxiliary air is pumped into the exhaust gas stream to help burn unburned hydrocarbons. The so-called "smog-pump". Air pumps wear out and lose efficiency, (if not disconnected, check hoses). It may need to be replaced, too.
The entire engine running lean could be caused simply by a partly clogged fuel filter. Check fuel pressure, under load if possible. If it's low even at idle, replace the filter. Other causes for lean running, oxygen sensors, would be picked up by the computer and called out trouble codes of their own. imp
#10
The added air due to vacuum leak results in a leaner run, O2 sensors tell PCM about it, and it can add fuel to compensate, to brings things up to "spec", up to a point.
Or, I could be full of ****! So, if a vacuum leak is found, and fixing it solves the lean code(s), please let me know, and I can slink away! imp
Last edited by imp; 08-16-2013 at 07:48 PM. Reason: spelling, and I ought to keep my big mouth shut, lol