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Go Back   TDIClub Forums > TDI Model Specific Discussions Areas > VW MKIV-A4 TDIs (VE and PD)

VW MKIV-A4 TDIs (VE and PD) This is a general discussion about A4/MkIV Jetta (99.5-~2005), Golf(99.5-2006), and New Beetle(98-2006). Both VE and PD engines are covered here.

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Old November 15th, 2019, 05:17   #1
jbuddy
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Join Date: Sep 2008
Location: Hampton NB
TDI(s): 03 Jetta TDI
Default studder at idle

I replaced my fuel pump on my standard 2003 jetta alh with an 11mm pump and now the car idles really rough most of the time. Group 1 IQ shows 0.8
I tried adjusting the IQ with vcds to bring it up but just made it worse so
put it back to stock. I changed fuel filter and preheater valve as well.
Did a diesel purge. I"m puzzled, any ideas what I should try next.
thanks
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Old November 15th, 2019, 08:00   #2
jokila
 
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Join Date: Dec 2004
Location: Houston, Texas
Fuel Economy: 52/45/40
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It needs to go up. It is too low.

Where did you get the pump? Used or new?
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Old November 15th, 2019, 09:00   #3
csstevej
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Yeah you need to raise it up to about 4-4.5.
If you cannot do it through VCDS than you may need to do the hammer mod.
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Old November 15th, 2019, 12:06   #4
BobnOH
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Join Date: May 2004
Location: central Ohio
Fuel Economy: 50/45/35
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Never seen one that low, (0.8). Car wants to see Injected quantity: 2.2 - 9.0 mg/H, ECU takes over from there. Most factory set at 2.2, don't know if that's any different for 11mm pump, shouldn't be. This has been discussed ad nauseam, most like a number around 4, but it should operate anywhere within range.
Seems counter intuitive, but hammer mod seems to work best in cases like yours. Loosen, hit it (youtube has video), tighten, then fine tune with VCDS as you like.
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Old November 16th, 2019, 09:26   #5
Mongler98
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Fuel Economy: Race: 12mpg, Gandma:65mpg
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0.8 is crazy low, i cant belive it actually runs. i would suspect your timing might be off a bit and thus it can run this low. the most i have seen is 1.4 to run properly at idle. I ran 1.2 to 1.4 on my AHU but it did shudder now and again randomly at stops but not enough to give 2 s's
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Old November 16th, 2019, 09:27   #6
Mongler98
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You need to hammer mod your IP. look it up. its easy to do.
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Old November 21st, 2019, 19:55   #7
jbuddy
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Location: Hampton NB
TDI(s): 03 Jetta TDI
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So it was a used 11mm pump. I loved the power but fuel mileage dropped

and of course at idle it was really rough. I put another 10mm pump on

and it idles perfectly however on a hill under load it went into limp mode.
It hadn't gone into limp mode for the month I was driving it with the 11mm
pump. I don't understand that, any ideas? Fuel mileage is more important
to me so now I have to determine why limp mode. Code p0299 came up.
Underboost. Timing is retarded and needs to be advanced which I will do
this weekend. If 11mm pump would have idled properly and mileage not so
bad I think I would have stayed because the power was awesome.
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Old November 21st, 2019, 20:38   #8
Prairieview
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Why didn't you put an ounce of effort into the 11 pump as the responders encouraged you to do?
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Old November 22nd, 2019, 19:06   #9
csstevej
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SERIOUSLY......have you not read the previous posts ???
The fix would have taken you about 10 mins........ not a couple of hours to swap out pumps and retime the engine.
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