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HELP!!!!!! P0401 to P0402

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  #1  
Old 06-12-2007, 11:19 AM
bigbadben bigbadben is offline
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HELP!!!!!! P0401 to P0402

A while back, I had the P0401 code come up on my 2001 Ford F-150 4.6 V-8.
The truck would sputter and surge at low speeds.

I searched on here for help and then did the following things:

Replaced the DPFE Switch
Replaced the EGR Valve
Removed and cleaned the Throttle Body. (Loads of carbon in the ports)
Replaced the Throttle Body Gasket
Replaced Spark Plugs
Replaced Fuel Filter

The truck ran fine for a day or two then started the surging again.

Then I got the CEL, and now this time, its P0402. I go from Insufficient Exhaust Gas Recirculation to Excessive. I am at my wits end. Im about to take it to a shop.

Any advise before I bite the bullet & put a big dent in my wallet?
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Old 06-12-2007, 01:54 PM
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KingRanchMan02 KingRanchMan02 is offline
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Vacuum leak! Check the rubber elbow at the back of the intake manifold. Good luck!
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Old 05-22-2008, 06:47 PM
cmbonandon cmbonandon is offline
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P0402

I am getting the P0402 code on my 2002 Ford F150. Yes it sputters sometimes at low speed. I changed the EGR and cleaned out all of that crap that throttle body. It worked for about 3000 miles and now it's back on and sputtering again. Vacuum leak? is that hard to get to? Is that gasket hard to get to. Becuase I too don't want to crap open the piggy bank. Please advise
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Old 05-22-2008, 07:50 PM
scratchanddent scratchanddent is offline
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i have a 97 f150 4.6 doing the same sort of thing. p0402, stumbly/shaky engine performance. i have worked through most of the same fixes: clean throttle body, replace most of the egr parts, plugs, wires, etc.... i'm thinking of replacing the vacuum hoses throughout. still not sure if this is going to solve anything, does this code pop up from maf or o2 sensors? this sort of thing seems way too common for there to be so many gremlins to hunt down in these engines.....
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Old 05-29-2008, 08:58 AM
beannerb beannerb is offline
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codes 401 402

I have a 97'ford f-150 4.6l gave me po401 po402 codes gave it smoke test and the iac idle air control was leaking jusr a suggestion that was after three trips to garage.
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Old 05-29-2008, 07:10 PM
sheetsd66 sheetsd66 is offline
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Sputtering and surging at low speeds sounds like a vacuum leak. Check the entire PCV circuit. The rubber elbow on the intake is the usual suspect, but the rubber connector on the PCV valve end deteriorates and causes problems, too.

Make sure the new DPFE you put on there was a genuine Ford/Motorcraft part and clean the carbon deposits from behind the throttle plate.

Will a leaking IAC valve throw a 0401/0402 code? I know a bad one will cause idle issues, but I never heard of it causing a code. That's a new one.
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Old 05-30-2008, 07:50 PM
Lance1601 Lance1601 is offline
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Ditto on the Ford DPFE sensor.
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Old 06-04-2008, 08:04 PM
eallanboggs eallanboggs is offline
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When a IAC fails it usually fails shut causing the engine to stall at idle. That's the opposite of a leak. What would cause excessive flow whether real or perceived. If the EGR valve is sticking open when not being commanded to open. Or is the DPFE could erroneously report that the EGR is flowing when it is not.
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Old 06-04-2008, 10:21 PM
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I've replaced IAC's before and they had problems on idle. Some wouldn't. My 01 F150 with the 4.6-v6 has had the DPFE replaced twice in 131.8k. The truck never missed a beat. Run like a new one. Just turned on the light. Didn't even effect my milage.
I don't remember the code number, but recently went thru a leaking upper intake manifold gasket. Turned on the "Check Engine" light, and went from atleast 400 miles on a tank of fuel, to 325 a tank. Yes it's been fixed.
Bob
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Old 06-04-2008, 10:23 PM
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I don't remember codes, but that sounds like missfire code for cylnder's one and two......
Bob
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Old 06-05-2008, 01:40 AM
eallanboggs eallanboggs is offline
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Misfire is P0300 to P0308. P0300 is random whereas P0301 to P0308 are cylinder specific.
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