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My 04 Taurus 3.0 vulcan, 98k mi, had a CEL turn on and I took it in to autozone and got The lean codes P0171 and P0174 as well as P0420 and P0430 which are both cat efficiency for each bank. The guy there thinks its a vacuum leak or MAF sensor. I just bought the car and the guy said he changed the spark plugs and wires less than 30 days ago. The car started running bad at idle and basically feeling like it is going to stall out at red lights. When I give it some gas it seems to run fine, with no noticeable loss of power and cruises just fine. It's only at idle that the RPM's drop to 600-800. When I cold start the car the RPM's jump up to about 2000 and sit there for a bit and then drop to 1000 and then lower and the sputtering starts. I was wondering if this has happened to anybody and also if I should even drive it the couple miles to the auto parts store or if it is risking melting something.
 

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Bad news- your cats may already be toast. But maybe not. Check all vacuum lines in the egr system, replace the dpfe (its a little rectangular black thing with a couple vacuum lines and an electrical connector.) That is the most common part to go bad in the egr system. Then clear the codes. The rpms going up to 12/1400 and then dropping to 750/850 at first, and especially cold startup, is normal. Obviously rough idle and stumbling/ stuttering is not. If the idle is better and no light after 50 miles, then you should be ok.
 

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Before you go further, check this thread IRC gasket leak. I'm sure that is the source of the p0171 and p0174's. This is a very common issue on the '04-up Vulcan engines, and when left running lean for too long, the converters need to be replaced. Replace the gasket, clear the codes, and see what happens from there.
 

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Discussion Starter · #6 ·
QUOTE (austex04 @ May 26 2010, 07:59 PM) index.php?act=findpost&pid=807137
Before you go further, check this thread IRC gasket leak. I'm sure that is the source of the p0171 and p0174's. This is a very common issue on the '04-up Vulcan engines, and when left running lean for too long, the converters need to be replaced. Replace the gasket, clear the codes, and see what happens from there.[/b]
If that IRC gasket is what is circled on the picture on the thread that was the exact source of the vacuum leak! I fixed the leak yesterday and the idle problem was solved. I drove the car and all seems well. I can almost swear I hear a slight hissing, but its hard to tell that close to the engine. After removing the cowl I was able to figure it out with some carb cleaner. However the CEL just came on again so I gotta go see what codes are spitting out now. I hope in that time it didn't do any damage to the cats! Thanks for the help! I'll let you guys know!
 

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You may also want to consider replacing the o2 sensors if your cats are toast, they start to read lazy with age, or if you had a too lean/rich condition for a while.
 

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QUOTE (goodbrosUIT @ May 26 2010, 09:12 AM) index.php?act=findpost&pid=807004
Bad news- your cats may already be toast. But maybe not. Check all vacuum lines in the egr system, replace the dpfe (its a little rectangular black thing with a couple vacuum lines and an electrical connector.) That is the most common part to go bad in the egr system. Then clear the codes. The rpms going up to 12/1400 and then dropping to 750/850 at first, and especially cold startup, is normal. Obviously rough idle and stumbling/ stuttering is not. If the idle is better and no light after 50 miles, then you should be ok.[/b]
These are great strategies and you might also check your IAC valve, that's a pesky little thing and it almost always seems to be in alignment when these codes are coming up. Just a thought.
 

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QUOTE (infnitymethod @ May 27 2010, 12:21 PM) index.php?act=findpost&pid=807216
QUOTE (austex04 @ May 26 2010, 07:59 PM) index.php?act=findpost&pid=807137
Before you go further, check this thread IRC gasket leak. I'm sure that is the source of the p0171 and p0174's. This is a very common issue on the '04-up Vulcan engines, and when left running lean for too long, the converters need to be replaced. Replace the gasket, clear the codes, and see what happens from there.[/b]
If that IRC gasket is what is circled on the picture on the thread that was the exact source of the vacuum leak! I fixed the leak yesterday and the idle problem was solved. I drove the car and all seems well. I can almost swear I hear a slight hissing, but its hard to tell that close to the engine. After removing the cowl I was able to figure it out with some carb cleaner. However the CEL just came on again so I gotta go see what codes are spitting out now. I hope in that time it didn't do any damage to the cats! Thanks for the help! I'll let you guys know!
[/b][/quote]
hey,where did you get the gasket,i might need one,but no one in this area has one.i tried to use and oil filter gasket but it dosent seem to fit(valve will not go all the way back in,gasket is to thick)
 

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The one circled in red is called an IAC Valve and it has to do with vacuum. When a car tends to do the lurching and hesitating I first check for misfires. Plugs wires coil, then IAC Valve. If you have replaced plugs and wires and still have hesitation I always ask people to re-check that they haven't disconnected the IAC Valve (this can happen when hooking up wiring or harness). Second plan of action is to check the fuel filter and any other vacuum lines. If you do not know the maintenance history on a vehicle then the best course of action is to replace the part that is giving you trouble. :)
 

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If it were mine, I would pull the upper intake and replace all the gaskets, and from there I would get a clear view of the vacuum hoses. Replace any that are cracked or split. Also replace the PCV valve, use an OEM valve, its worth it. That should resolve your 171 and 174 codes.
 

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My 04 Taurus 3.0 vulcan, 98k mi, had a CEL turn on and I took it in to autozone and got The lean codes P0171 and P0174 as well as P0420 and P0430 which are both cat efficiency for each bank. The guy there thinks its a vacuum leak or MAF sensor. I just bought the car and the guy said he changed the spark plugs and wires less than 30 days ago. The car started running bad at idle and basically feeling like it is going to stall out at red lights. When I give it some gas it seems to run fine, with no noticeable loss of power and cruises just fine. It's only at idle that the RPM's drop to 600-800. When I cold start the car the RPM's jump up to about 2000 and sit there for a bit and then drop to 1000 and then lower and the sputtering starts. I was wondering if this has happened to anybody and also if I should even drive it the couple miles to the auto parts store or if it is risking melting something.

i had the same problem for the last few days and it ended up being a vacuum hose, very easy cheap fix.... just check the hoses by and around the air filter...
 

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Whoa whoa whoa let's not get ahead of ourselves...replacing cats and O2 sensors. This is a code for lean on BOTH banks. This leaves only a few options. The BEST way to start troubleshooting a lean condition on both banks is to unplug the MAF connector. If the car runs better with the MAF unplugged, then the MAF is either dirty or malfunctioning and needs to be cleaned or replaced. If the car doesn't run any better, then the MAF isn't the culprit, and you are likely to be looking at a vacuum leak. Of course, it would be one that affects BOTH banks (this is important!).
 
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