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I have a 1997 Ford Taurus LX 3.0 DOHC. The car runs beautifully, but failed smog with high HC. I've replaced Spark plugs, wires, coil, egr valve, all 02 sensors, maf sensor, coolant temperature sensor, air temperature sensor, pcv valve, numerous hoses, vacuum lines, vacuum fittings/connectors, air filter. I have not yet retaken the smog test, but right after I replaced the maf sensor, coolant temperature sensor, and air temperature sensor, I now have the check engine light on after those three things replaced. The code is P0174 which means lean fuel mixture, from what I have gathered on the internet, but what else can be causing this? I'm perplexed.
 

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If there is no current or pending 171, intake gaskets are a definite possibility. I would check LTFT on bothe banks at idle and at 50 mph cruise and report back with the numbers.

Why did you replace the MAF, IAT, and ECT? Throwing random parts at a problem gets expensive real quick, and likely won't solve the problem.
 

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First thing I would do is perform a smoke test. P0171/174 are almost always a vacuum leak. The trick is finding it(hence the smoke test)
 

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First thing I would do is perform a smoke test. P0171/174 are almost always a vacuum leak. The trick is finding it(hence the smoke test)
Sometimes you can take the short cut and just listen::lol2:

Last two times I left a hose off, I did just that. Works.

But if I make the same misake 3 times, I had better go back to school.

-chart-
 

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Discussion Starter #6
arrrgghhh

If there is no current or pending 171, intake gaskets are a definite possibility. I would check LTFT on bothe banks at idle and at 50 mph cruise and report back with the numbers.

Why did you replace the MAF, IAT, and ECT? Throwing random parts at a problem gets expensive real quick, and likely won't solve the problem.
I paid for a report from smogtips.com and they told me It's probably the maf sensor. So I replaced it. but actually took it off because over a weeks time, I ended up having 5 codes pop up. Once I put the old MAF sensor back in, all the codes went away. Now, Since my initial post, I have replaced every vacuum line and fitting, so within those lines, I don't have any vacuum leaks. Today I just came back from another smog test, and failed on HC only at 15 mph test max allowed is 52ppm, and it measured 61ppm FAIL. it passed on the 25 mph test (however, it measured at the highest level allowed) Max allowed is 36ppm, measured at 36ppm PASS.

I took the car to a mechanic, he told smoked the car and told me I have no leaks in the engine compartment. He told me I did have an exhaust leak somewhere. I took the car to a muffler shop, they found holes near the rear catalytic converter and repaired them. this is where I am at today. With a second failed emissions. again with high HC, however, i've somehow lowered the HC's a bit, since the last test 2 months ago. I don't have any more money to throw at it, and two mechanics worth of 120 to 125.00 a pop for diagnostics, only to tell me I had codes in the car. nothing pointing me in any direction to fix anything. I always thought a diagnostic was a diagnosis to find specific problems, not tell me, well, if you fill the tank with chevron premium, and add a can of techraline into the tank, drive it until its gone, then come back to me..

You see, I'm just not faithful in todays mechanics that I've recently paid hard earned money to.
 

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The three main causes of high HC are:
1. Lean Misfire
Check for leaks, including the vacuum distribution box that the brake booster is connected to. and even the booster. Push brake pedal to the floor a few times with engine off. Hold pedal down and start it up. The pedal should rise up as vacuum builds up. If not, the booster is leaking.
2. Weak ignition. Worn plugs, wires and weak coil/coil packs
3. Bad cat converter. With the engine cold, knock on them. if they sound like marbles inside they have melted.
 

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I paid for a report from smogtips.com and they told me It's probably the maf sensor. So I replaced it. but actually took it off because over a weeks time, I ended up having 5 codes pop up. Once I put the old MAF sensor back in, all the codes went away. Now, Since my initial post, I have replaced every vacuum line and fitting, so within those lines, I don't have any vacuum leaks. Today I just came back from another smog test, and failed on HC only at 15 mph test max allowed is 52ppm, and it measured 61ppm FAIL. it passed on the 25 mph test (however, it measured at the highest level allowed) Max allowed is 36ppm, measured at 36ppm PASS.

I took the car to a mechanic, he told smoked the car and told me I have no leaks in the engine compartment. He told me I did have an exhaust leak somewhere. I took the car to a muffler shop, they found holes near the rear catalytic converter and repaired them. this is where I am at today. With a second failed emissions. again with high HC, however, i've somehow lowered the HC's a bit, since the last test 2 months ago. I don't have any more money to throw at it, and two mechanics worth of 120 to 125.00 a pop for diagnostics, only to tell me I had codes in the car. nothing pointing me in any direction to fix anything. I always thought a diagnostic was a diagnosis to find specific problems, not tell me, well, if you fill the tank with chevron premium, and add a can of techraline into the tank, drive it until its gone, then come back to me..

You see, I'm just not faithful in todays mechanics that I've recently paid hard earned money to.
I totally understand your frustrations. Way too many mechanics these days basically refuse to diagnose problems. It turns into "It's doing this" - "Well, start by throwing THESE specific parts at it and then get back to me". It's happened to me before. It's actually what got me to start doing my own diagnostics and work. At least I know that I actually give a damn about the correct operation of my vehicle...

It seems to be chronic to certain areas and shops too. If you ever find a good shop, remember it - because it's becoming a rarity.

Anyway, as others have mentioned, probably 90% of the stuff you bought didn't need to be changed. I know the MAF in particular is quite expensive, and it sounds like the one you bought was defective anyway since it tripped a bunch of codes.

As for the actual issue, since you're fairly likely good on the vacuum side (unless hoses were swapped somewhere by chance, might be worth triple checking), it's very likely one or more of the catalytic converters isn't doing anything, OR, you have a physical engine issue causing lean burn (valve seat problem, piston ring blowby/cylinder wall scoring, etc)
 

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I paid for a report from smogtips.com and they told me It's probably the maf sensor. So I replaced it. but actually took it off because over a weeks time, I ended up having 5 codes pop up. Once I put the old MAF sensor back in, all the codes went away. Now, Since my initial post, I have replaced every vacuum line and fitting, so within those lines, I don't have any vacuum leaks. Today I just came back from another smog test, and failed on HC only at 15 mph test max allowed is 52ppm, and it measured 61ppm FAIL. it passed on the 25 mph test (however, it measured at the highest level allowed) Max allowed is 36ppm, measured at 36ppm PASS.

I took the car to a mechanic, he told smoked the car and told me I have no leaks in the engine compartment. He told me I did have an exhaust leak somewhere. I took the car to a muffler shop, they found holes near the rear catalytic converter and repaired them. this is where I am at today. With a second failed emissions. again with high HC, however, i've somehow lowered the HC's a bit, since the last test 2 months ago. I don't have any more money to throw at it, and two mechanics worth of 120 to 125.00 a pop for diagnostics, only to tell me I had codes in the car. nothing pointing me in any direction to fix anything. I always thought a diagnostic was a diagnosis to find specific problems, not tell me, well, if you fill the tank with chevron premium, and add a can of techraline into the tank, drive it until its gone, then come back to me..

You see, I'm just not faithful in todays mechanics that I've recently paid hard earned money to.
Just a thought, fuel filter and fuel pressure regulator can cause lean, same as vac leak.

-chart-
 

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I had a lean code (one of many) when I inherited my bull, I cleaned the MAF sensor with CRC sensor cleaner, repaired the large hole in the vacuum tube near the PCV valve, (the sucking sound made it easy to find), changed the plugs, leads and distributor cap and the lean code went away (and the overall engine performance and idle improved considerably!).
 

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Discussion Starter #13 (Edited)
My car is running beautifully.. after running premium fuel, a bottle of chevron fuel system cleaner, another tank of premium fuel, a bottle of cataclean, another tank of premium fuel, and a bottle of guaranteed to pass, I tell ya, this car has never run so much better. it's quiet, zippy, and really fun to drive. However.. The slightly high hydrocarbons makes me fail the emission test. Every time I take it to a mechanic, they each have some idea and they are all different from one another. Should I just take it to a ford dealership? I'm thinking that nobody wants to diagnose a car any more. Ford Dealerships do... don't they? I do not want someone working on my car that just wants to replace things rather than diagnose until the problem is found. so far I've spent over 370.00 just trying to diagnose the cause of the problem. I am really considering moving out of California, just to get away from their over zealous emissions laws.
 

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Hmm. Ask VW for a copy of their ecu software?! :D

Seriously, maybe it's time to get your Bull's cat looked at....
 

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How many miles on this car? Does it burn/consume oil? Have you done a cylinder compression check? Have you re-checked for vac and exhaust leaks using
? You can also use the stethoscope to listen for an even clicking come from each fuel injector at idle (if uneven, an injector is sticking).

I have used Cataclean for many years with great results. Sometimes, with an old car, you may have to use five tankfuls to fix your troubles. Also, 30 WOT blasts from 50-80 MPH on an open highway cures this sort of problem.
 
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