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When you had the throttle pot checked out did you make sure the idle switch was working correctly ?
I remember someone on here had a problem with that and it caused lean issue.
Hi James, i might take you up on that as i'm sick of paying vag prices for parts that make no difference! Just paid £135 for a genuine oxy sensor this morning. Also just swapped the injector rails car to car and that made no difference either. By process of elimination it must be the pump!!!
I'll get the boost kit sent back on monday too - thanks again for that
When you had the throttle pot checked out did you make sure the idle switch was working correctly ?
I remember someone on here had a problem with that and it caused lean issue.
Thanks. while at a 'loose end' i just swapped throttle bodies complete, car to car - made no difference!
James, may still take you up on your offer for loan of the pump but, had anyone around nottingham got one i can borrow? New or known good used would be ok, i would leave a deposit of some kind. This evening or tomorrow morning if at all possible?
Having read through the entire thread (to date), I am surprised that nobody red flagged the fuel pressure level on boost. Remember that the AAN fuel pressure regulator is designed to maintain a 4 bar pressure differential across the fuel injector, as explained here:
The Audi Enthusiast website. Forums for all Audis including A4, S4, A5, S5, A6, S6, allroad, A8, S8, TT, R8, Q5, Q7, 4000, 100, 200, v6, v8, vintage, local forums
On that basis, when you are "on boost" the fuel pump has to supply enough fuel at 4 Bar *PLUS* at least the boost level, i.e. stock = about 4 Bar + 1.2 Bar = 5.2 Bar; Chipped = 4 Bar + 1.5 Bar =5.5 Bar and Mad RS2 (plus) = 4 Bar + 1.9 Bar = 5.9 Bar. Therefore, in all cases, getting only 5 Bar "on boost" = not enough pressure = lean conditions.
So you have three choices: replace the OE fuel pump, add an auxiliary fuel pump relay or add a 044 type pump (probably best with the auxiliary fuel pump relay). Here are some potentially useful posts:
The Audi Enthusiast website. Forums for all Audis including A4, S4, A5, S5, A6, S6, allroad, A8, S8, TT, R8, Q5, Q7, 4000, 100, 200, v6, v8, vintage, local forums
The Audi Enthusiast website. Forums for all Audis including A4, S4, A5, S5, A6, S6, allroad, A8, S8, TT, R8, Q5, Q7, 4000, 100, 200, v6, v8, vintage, local forums
In the meantime, try to stay out of the boost.
RS2'd 93 UrS4 5 spd sedan
94 UrS4 V8 6 spd manual avant
Having read through the entire thread (to date), I am surprised that nobody red flagged the fuel pressure level on boost. Remember that the AAN fuel pressure regulator is designed to maintain a 4 bar pressure differential across the fuel injector, as explained here:
The Audi Enthusiast website. Forums for all Audis including A4, S4, A5, S5, A6, S6, allroad, A8, S8, TT, R8, Q5, Q7, 4000, 100, 200, v6, v8, vintage, local forums
On that basis, when you are "on boost" the fuel pump has to supply enough fuel at 4 Bar *PLUS* at least the boost level, i.e. stock = about 4 Bar + 1.2 Bar = 5.2 Bar; Chipped = 4 Bar + 1.5 Bar =5.5 Bar and Mad RS2 (plus) = 4 Bar + 1.9 Bar = 5.9 Bar. Therefore, in all cases, getting only 5 Bar "on boost" = not enough pressure = lean conditions.
So you have three choices: replace the OE fuel pump, add an auxiliary fuel pump relay or add a 044 type pump (probably best with the auxiliary fuel pump relay). Here are some potentially useful posts:
The Audi Enthusiast website. Forums for all Audis including A4, S4, A5, S5, A6, S6, allroad, A8, S8, TT, R8, Q5, Q7, 4000, 100, 200, v6, v8, vintage, local forums
The Audi Enthusiast website. Forums for all Audis including A4, S4, A5, S5, A6, S6, allroad, A8, S8, TT, R8, Q5, Q7, 4000, 100, 200, v6, v8, vintage, local forums
In the meantime, try to stay out of the boost.
Thats fantastic - thanks a million!
For this year i will probably replace the oe pump with a stock item as i'm only running 1.4 boost pressure. Big BHP will come later!
As for staying out of the boost - yeh i totally agree! It makes me shudder to thing how i've been driving the car whilst putting up with this, only a month ago i 'struggled' to see 140!!! Not on a uk road of course!
Yeah but if he is only getting 1 bar boost that 5bar fuel pressure is correct...
I think it could be a fuel pump issue causing lean running, but if it is not making target boost (say 1.2bar) then there is likely an air leak - and unmetered air will also lead to lean running.
I would fix the air leak first.
Paul
Originally posted by UrS4boy
Having read through the entire thread (to date), I am surprised that nobody red flagged the fuel pressure level on boost. Remember that the AAN fuel pressure regulator is designed to maintain a 4 bar pressure differential across the fuel injector, as explained here:
The Audi Enthusiast website. Forums for all Audis including A4, S4, A5, S5, A6, S6, allroad, A8, S8, TT, R8, Q5, Q7, 4000, 100, 200, v6, v8, vintage, local forums
On that basis, when you are "on boost" the fuel pump has to supply enough fuel at 4 Bar *PLUS* at least the boost level, i.e. stock = about 4 Bar + 1.2 Bar = 5.2 Bar; Chipped = 4 Bar + 1.5 Bar =5.5 Bar and Mad RS2 (plus) = 4 Bar + 1.9 Bar = 5.9 Bar. Therefore, in all cases, getting only 5 Bar "on boost" = not enough pressure = lean conditions.
So you have three choices: replace the OE fuel pump, add an auxiliary fuel pump relay or add a 044 type pump (probably best with the auxiliary fuel pump relay). Here are some potentially useful posts:
The Audi Enthusiast website. Forums for all Audis including A4, S4, A5, S5, A6, S6, allroad, A8, S8, TT, R8, Q5, Q7, 4000, 100, 200, v6, v8, vintage, local forums
The Audi Enthusiast website. Forums for all Audis including A4, S4, A5, S5, A6, S6, allroad, A8, S8, TT, R8, Q5, Q7, 4000, 100, 200, v6, v8, vintage, local forums
Its running 1.4 bar of boost, and has been leak tested with spinks tester kit, lead to new induction pipe and somco boost hoses - problem is still there!
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