Intermittent starting A4

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DJDaz

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Hi hopefully someone can point me in the right direction. I have developed over the last few months an issue when I start my 2007 A4 Convertible 2.0 TFSI petrol. Sometimes it starts fine no issues at all, other times it cranks over and starts but with a light on my dash EPC I think it is and no power, it’s in limp mode.
if I turn it off and on a couple of times it often clears itself and the car runs fine.
I have been told it’s the high pressure fuel pump but I am not fully convinced at it is random
any steer would be appreciated
 
Reactions: Charlie Farley and northpole
Have you run any diags yet , if not VCDS would be a good start.
 
Reactions: DJDaz and northpole
There is a known issue with 2 relays in the ecu box that control numerous functions inc starting and related systems, they can break down and cause this issue, when you run a diag it brings up a lot of faults that have one common factor, they are all electrical.

Ive had the same issue and it would cause random starting issues , limp mode and ECP lamp , sometimes running really rough, it slowly gets worse as the relays start to fail to the point it just gives up all togrether.
 
Reactions: DJDaz and northpole
Do you suffer from sessions where it takes several times in one go to fire up , then fine for a few days then back to the random starting issue.
 
Reactions: northpole
these.
only one the main culprit but most chaps replace both.
 
Reactions: DJDaz and northpole
I'll look back and see if i can find the info page with the fault specifics.
 
Reactions: DJDaz and northpole
Charlie Farley said:
Have you run any diags yet , if not VCDS would be a good start.
Click to expand...
Hi Charlie, I did run diagnostic using my unit and it did throw up about 4 codes but it’s not VCDS so that may shed more light thanks
 
Reactions: Charlie Farley
This exactly what is happening, great help and thank you
 
Reactions: Charlie Farley
Charlie Farley said:
Do you suffer from sessions where it takes several times in one go to fire up , then fine for a few days then back to the random starting issue.
Click to expand...
Yes it drives me mad, I started to think it was a broken wire, I had checked as many as I could reach or see, perhaps these relays are the issue, I have a new pump on order just in case but returnable thankfully if it proves these relays are the issue.

614 & 644 are the relay number I take it
 
Reactions: Charlie Farley
The two relays have a superseded part number now,
I'll check, if you search my previous post you will see my thread about the problem and the new part numbers.
It is a really infuriating problem as such a simple relay failing throws up so many possible faults which they are not.
 
Reactions: DJDaz
here you go, my original thread which all came down to these two relays, well probably only one but replaced both to be 200% and its been fine ever since, well it was fine as soon as i replaced them albeit twice.

Random turbo solanoid , bypass control ,evap and fuel pump errors.

Today the old bus has decided to misbehave again and throw up the EPC lamp again. Having replaced the N80 last week things have been fine , today jumped in and bang EPC lamp's on and the old bus is running like a 2cv. Restarted it a few times and it cleared but vcds has logged a rather...
www.audi-sport.net
 
Last edited:
the relays were originally 614 but changed to 644.
 
Thanks, I just read your old thread and funny enough I have the same codes, I do remember about 2 years ago the fuel pump relay failed and that was changed for one from the dealership, i think it’s worth picking up a couple and giving it a go next week.
frustrating as when it is running it’s like a rocket
 
Reactions: Charlie Farley
The only downside is getting into the bottom of the ECU box, it is a right pain just to swap over a relay or two, not one of Audis better designs.
 
Charlie Farley said:
The only downside is getting into the bottom of the ECU box, it is a right pain just to swap over a relay or two, not one of Audis better designs.
Click to expand...
Hi Charlie,I did check the relay under the ECU, bit fiddly and your right not the best design lol, I had changed one before and that was a 644, so I tried the dealer for another relay to be told it could take 4 days, so I paid £12 from Just German Parts and that arrived next day.
So I swopped out the other relay, found a pair of long nose pliers worked well, I cleared all codes after connecting the battery and the car started fine, the SRS light was on for about 500 yards and everything worked as it should, it’s been almost 3 weeks and the car starts every time, didn’t want to temp faith giving an update right away.
really wanted to say thank you for the help, I really do appreciate it.
 
Reactions: Charlie Farley
You are welcome chap ,allways good to hear of a happy ending to a persistent fault.

Rob
 
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