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ok guys here is what i am dealing with: I recently bought a 2001 mustang 3.8 V-6 used from an individual(this car was bought for my 17 year old Daughter). I made a good deal on the car and new it needed a little work, powersteeering pump whining, muffler sounded louder than normal, and a few interior cosmetic fixes. the car was in good shape, ran good, no smoke, dry underneath. well i get the car home and start on it. First the "service engine soon" light comes on. so i have a friend that does mechanic work on the side puts it on his scanner it shows an EGR code. He clears the code and recommends a Seafoam intake cleaning. he also tells me that someone has removed both Cat converters and that is the reason for the loud exhaust( converters are gone but the O2 sensors are still there). I do the seafoam cleaning and bring it back to him (service engine light came back on) so we pull the EGR valve and end up changing it. he tells me to drive it and see if the light comes back on. it does of course so he clears it again and i try to get it inspected and failed emmisions computer tests. I have saw on the forum about the EVR sensor, and the DPFE sensor may be bad, my question is what does removal of the converters do to the emmissions diagnostics?, will i need to put the converters back to pass the emmisions test? i have noticed the car runs rough when you hold the throttle between 1000 and 2000 RPM but only when the a/c is on. is this from the emmissions problem? any help will be greatly appreciated!!
 

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The DPFE should be the culprit for the EGR problem. Happened on my 96 3.8 (they're the same engine almost). Replaced that and all my problems went away. As for the running rough at those RPMs im unsure of. If it were me, I would start with cleaning the IAC with Carb cleaner and replacing spark plugs and wires if necessary. Hope this helps. Give us an update once you do a few more things to it.
 

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You pretty much need catalytic converters to pass emissions tests. Depends on whether your state requires you to do so whether you need them.

IAC is the Idle Air Control valve. It's a small piece on the top left side of the motor that you can pull off by removing 2 bolts and a power cable. There could be thick carbon deposits inside, which could be causing problems. If it's clean you should probably look elsewhere to fix your throttle issue.
 

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Welcome to the club of dads buying 2001 v6's for newly licensed daughters. Right now it's you and me.

Always post the engine codes when you get them.

The Idle Air Control (IAC) valve is a stepper motor-driven, vacuum leak. It is under computer control to manage the idle by introducing air around the throttle body. Basically pretending to hold the pedal down for you.

I have been pulling Windstar intakes for the VAP guy. I have seen several IAC's totally fouled up with carbon. The IAC has to be able to open and close to manage the idle. Pull it off and squirt the heck out of it with carb cleaner if you see anything black.

The EGR issue could be the DPFE.

The DPFE gets a bad rap but they do go bad. Its responsible for reporting on the state of the EGR valve. It does this by trying to sense the difference in pressure across two places in the pipe running up to the EGR. It can't do this if the EGR is fouled or if the EGR pipe is plugged. Be sure that you can blow out both lines running to the DPFE.

Emissions is another story.

You should be able to pass a tailpipe 'sniff' test if you have a clean air filter, good coil, wires, plugs and fresh oil. Ain't closed loop fuel injection wonderful.

Sadly, the engine computer is still going to rat you out.

This v6 has four O2 sensors. One function the computer is going to test is to compare the signals from the front and rear O2 sensors on each side. The signals will be the same if you don't have cats and you get the 'Service Engine Soon' light (P0420, P0430).

An MIL Eliminator will plug in line with the rear O2 sensors and fool the computer with a reduced signal. The front O2 sensors will still be part of the emissions system.

Hope this helps.
- the other Dad with a 2001 V6 for my Daughter
 

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yeah you need cats to pass the test for sure. try getting a handheld tuner or something like it too see if it can find the problem :smilie
 

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Discussion Starter #7
Thanks for the great info!!

wow thanks so much for all of the information guys! i just bought a scanner, and i am going to put all of what yall are telling me to work this weekend! I will keep yall posted as to what i find next week. Thanks again to all that replied. its nice to know there are knowledgeable folks out there willing to take time to help someone!! wish me luck!! everyone have a great weekend!!!
 

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The manuals from the car parts store are lightweight compaired to the shop manuals but they often include good diagrams.

The plug wiring is a good example. This was just covered in V6 Tech "how to connect spark plug wires"
 

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Discussion Starter #9
One problem down!!!

well, the DPFE sensor was the culpret for the PO401 code! and fixed the rough running at mid throttle. the car runs great, new plugs,plug wires. cleaned the IAC controller. Im getting a pending code now PO420 Catalyst system efficiency below threshold bank 1. so i am ordering a set of MIL eliminators today!
 

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keep in mind the mil eliminators replace the rear O2s.. unless you already knew that, then disregard
 

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Who saw the P0420 coming!

...while we are in the spirit of full disclosure, the MIL eliminators that I have seen go inline WITH the rear O2 sensors, reducing their signal and shifting the signal in time.

There have to be O2 sensors downstream to provide a signal to the MIL E.

Heaping GOBS of detail:
TeamNECO - MIL Eliminator How To
 

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...one more thing...

This is what the front half of the exhaust should look like:
Buy Walker Catalytic Converter - ULTRA Direct Fit 50529 at Advance Auto Parts

If you zoom in on the engine end you will see that the O2 sensor ports are immediately before and after the cats. Earlier models had O2 sensors in the manifolds.

If your cats are missing, you could go this route or have a replacement welded in.
 

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Discussion Starter #13
ok guys, i installed the MIL eleiminators in the downstream o2 sensors, and cleared the codes. my daughter has been driving it since saturday and the engine light is still off. im going to put my scanner on it today and hopefully get the emissions test passed!!! i will let yall know what happens. Also i have been bitten by the mustang bug!! i am looking for a car for myself (Project Car) i prefer the 1999 to 2004 bodystyle and definately want a GT no less!! if anyone nhas any leads let me know!!
 

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Glad to hear the good news!

Why bother with the GT when you can have so much fun with the V6! ;-)

You will also be that much smarter if the daughter has any issues.

I am 2/3 rds of the way into installing the Windstar upper intake manifold. (too dang hot to be outside right now)

Good luck to you and your girl!

- dan
 

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Discussion Starter #15
Thanks for the great info!!

well guys she passed the Emissions test with no cats haa!! (isnt the info you get on the internet great) my baby girl is good to go!! its sooo nice to know that i can now build a street rod that can "BREATHE" and still pass emissions. I cant wait to get started on mine!!!!!!! I am looking for some suggestions on a different muffler, single or duals? The car just doesnt sound right with no cats and a stock muffler. what are some suggestions on a exhaust for this V6er? and again thanks soo much to all who gave me such valuable info!!!
 

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Way to go! (Virtual high five) (fist bump is for the kids)

I wouldn't ever remove the cats but in your case you didn't have them in the first place.

Be sure and do a thourough tune up (i.e. oil, filters, seafom, gap plugs) before the next tailpipe sniff test. ...we really should be doing this anyway.

When you find your black '99-'04 V6 5 speed, be sure and give Steven a call at VAPauto.com. I just finished my Windstar intake swap and I love it!


Don't be afraid of the check engine light. I picked up a pocket scanner at the parts store and have used it on several cars now.

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