hesitation

[andy123]

Can anyone help me please!! basically this all started a bit ago when i went to check on the condition of the recirc valves on my car.I felt like the car wasnt 100% and losing power.I removed the cover and found that one of the hoses coming off the top of the recirc valves leading to the t piece is split that goes to the n75 valve is split. I put some new forge valves on. I replaced this hose and when the car came on boost the power delivry became very uneven, and you could feel the car hesitating and then pulling again. This happened from 3k onwards all the way through the rev range. Ive had the car on VAGcom and the only problem was an intermittent fault with M AF. I replaced yesterday and still playing up. My question is would a faulty n75 valve show up on vagcom? when you remove the hose from the recirc the car runs better again, but underpowered. Im asuming this is because the car is running on a default program. Soon as you plumb everything back in the erraticness starts. Ive been told that an n75 woul show up on vag com but i reman unconvinced. At the same time i dont want to be swapping out parts if they arent knackered. any offers chaps?

[Dippy]

Is your car remapped for increased boost? If so then stronger DV springs may help.

[andy123]

no remaps, tottally standard apart from forge recircs. it just feels like the boost is fluctuating, but it stops when you remove the piping from the top of the dvalve. The way im seeing it is that it only happens when the n75 valve is brought back into the equation,, if you see what i mean.

[tartan_rob]

that sounds like your problem. about £45 from VAGPARTS. They do go from time to time.

[andy123]

is it difficult to fit? when swapping the recircs out i noticed that the pipework looks like all the turbo pipework is crimped on. I dont have the tools to recrimp the pipes so id have to use jubilees. is this acceptable?

[SimonS4MTM]

Jubilees are okay

[andy123]

lovely.been in touch with my local audi and they have it in stock. would use vagparts but got to go to herts tommorow. will i need a gas mask if im going down south by the way (hemel fire)??

[vw_nutta2]

no gas mask required, its all out, was quite a sight on tuesday.

[andy123]

right, fitted a new n75 the other day and its still running like a lemon. bit the bullet yesterday and went to audi stealership. They put it on vagcom or whatever it is they use and think its a fault in the wiring between the ecu and the n75. Which brings me on to my next question.... wheres the ECU? sorry for asking so much but ive only had the car a couple of weeks and im still finding my way around. The guy at the audi garage said they never had a fault with a wiring loom before and that it could be a faulty ecu?? this is turning into a real drama.. any suggestions??

[CliveH]

Andy,
ECU is located on the driver's side, right at the top of the engine compartment. You need to remove the protective cover, as if you were replacing the battery.
However, the ECU is literally a "black box" to which all the ECU inputs and outputs are connected. You will need some expert advice on tracking down which cable it is that goes off to the N75 actuator.

[CliveH]

PS most of the tuners carry spare stock ECUs for testing and emulation purposes and I'm sure they would be happy to switch them over to see if this is the fault - 5 minute job.

[andy123]

Cheers clive! I managed to get a Audi self study book on the s4 which has a full wiring diagram iirc. Anyone want a copy as i was going to scan it?

[Nige_RS4]

PS most of the tuners carry spare stock ECUs for testing and emulation purposes and I'm sure they would be happy to switch them over to see if this is the fault - 5 minute job.

Not quite 5 mins, the ECU has to be recoded to the car (and I presume the immobiliser function too).

I would doubt very much that it's the ECU - more likely to be a mechanical problem i.e. boost leak, or faulty bypass valve (recirc valves) - did you say you've checked these??

Nige.

p.s. can I borrow your 'orig' N75 valve?

[tartan_rob]

Nige - I have an N75 valve you can borrow (screw jammed though but works fine) - I have an RS2 one fitted now. drop me a PM.

Andy - you may already have tried this but why not take it back to dealer?

[CliveH]

OK Nige, maybe 10 mins then!

Andy/Nige, you may be interested in this :

http://cgi.ebay.co.uk/ws/eBayISAPI.dll? ... %3AIT&rd=1