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Discussion Starter · #1 ·
I had an old thread discussing an intake leak, and after months of trying to hunt this down I finally got the car to throw a p0455 Evap large leak code. I believe I did have an intake leak and fixed that, because the car is better off now than before, but still somethings up so here's what I've done so far. 2005 Ford Taurus 3.0 Vulcan engine. Auto Climate.
New Evap purge valve under hood and vent solenoid on the canister, new Egr and tube (Old one broke, go figure) all lines and electrical connections checked on the canister, and under the hood as far as I can tell. I can't find a good diagram of where the Evap line runs from under the hood to the tank/canister? So I haven't checked that one. I plan on hooking my smoke tester to the system but not sure the best way to do that for evap. Can I hook it in the line going from the canister to the fuel tank? I don't want any of the smoke oil to get in the tank, not sure if it would hurt anything there. New gas cap btw, and as far as I can tell the filler neck all looks good. Thought about popping it off to check the seal, but didn't want to accidentally cause another leak. Any suggestions on this system?
Car has 125k miles and symptoms are grumpy idle, loss of vacuum at high rpm (Vents blow out defrost), when letting off the gas above 50-55mph the rpms go down to 900 and bounces up and down until the car has slowed under about 45-40mph.
Edit-car doesn't have much if any odor btw. If anything, the exhaust from the pipe smells a little more yuck, but could just be me.
 

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Not log but I can read them with my scanner. Last I checked all seemed right at idle, airflow was a bit wonky if the engine was warmed up because the leak.
If your airflow at idle is "a bit wonky", you may have a dirty MAF. That could also cause issues at speed like you were mentioning.
 

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Discussion Starter · #5 ·
If your airflow at idle is "a bit wonky", you may have a dirty MAF. That could also cause issues at speed like you were mentioning.
I'll have to hook it up and read again. I think I was at speed when it seemed off. I have cleaned the maf with maf cleaner and cleaned the iac. Could need replacing maybe? But will a maf give an evap code?
 

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I'll have to hook it up and read again. I think I was at speed when it seemed off. I have cleaned the maf with maf cleaner and cleaned the iac. Could need replacing maybe? But will a maf give an evap code?
MAF rarely fail as they only see clean filtered air. However if that air is not clean then you can get dirt on the element.
-chart-
 

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It does have a new air and fuel filter. Not sure if it's already been damaged from before. I cleaned it after installing a new filter.
Pic of air plenum from the JY. Common issue. The oil is from the PCV being bad. This oil does not belong of course and any oil vapor will coat the MAF.
-chart-
 

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Discussion Starter · #9 ·
Pic of air plenum from the JY. Common issue. The oil is from the PCV being bad. This oil does not belong of course and any oil vapor will coat the MAF.
-chart-
Ok interesting. So this can throw a evap code? Didn't know the maf could cause an air leak like that. Should I then replace the pcv and maf? I removed my pcv to check the seal. It's a little flat, don't know how well it's actually sealing. Didn't look for oil inside the box but will check that now.
 

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Ok interesting. So this can throw a evap code? Didn't know the maf could cause an air leak like that. Should I then replace the pcv and maf? I removed my pcv to check the seal. It's a little flat, don't know how well it's actually sealing. Didn't look for oil inside the box but will check that now.
I would not recommend replacing a MAF to clear a EVAP code, two seperate issuses. If your idle airflow is wonky, then look at your MAF. For the EVAP code, I would either start replacing valves (that is guessing) or do a smoke test to look for leaks.
 

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Ok interesting. So this can throw a evap code? Didn't know the maf could cause an air leak like that. Should I then replace the pcv and maf? I removed my pcv to check the seal. It's a little flat, don't know how well it's actually sealing. Didn't look for oil inside the box but will check that now.
I think your engine performance issues are one thing, and the EVAP leak is a separate issue. In reality, the only way you can get both at the same time is if the evap purge valve isn't fully closing, since that's the only way you can get a vacuum leak into the engine without popping lean codes or showing high positive fuel trims(engine will constantly pull air from the fuel tank which has fuel vapors). On a scan tool you'd be able to see the vent valve on the tank trying to compensate for this leak. But since you said you already replaced that unit, I would assume that's not the issue since it's unlikely you had two bad ones in a row. The factory ones generally don't fail in the first place unless the charcoal canister fails.
 

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Discussion Starter · #12 ·
I would not recommend replacing a MAF to clear a EVAP code, two seperate issuses. If your idle airflow is wonky, then look at your MAF. For the EVAP code, I would either start replacing valves (that is guessing) or do a smoke test to look for leaks.
What's the best place to hook a smoke machine to the evap lines in this car?
 
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