UrS6 - Slight hic-cup between 2.5k and 3.5k rpm when hot ?

[UrS6 - IamS6]

No easy access to vag-com.

Don't understand the blink codes. Too busy driving the car every day tbh.

But notwithstanding the above, would anyone know what this might be.

When cold the fried otherwise standard car accelerates faultlessly, but when up to temperature, it has a slight hic-cup / two or three hic-cups between 2,500 and 3,500 rpm on WOT, powers on through and then revs clean again. The hic-cup is enough for a forum passenger to be aware of it, but no more, i.e. not half as violent as a boost cut.

It doesn't occur on slight or medium throttle application just WOT.

Spark plugs are new NGK. Mileage is 43k.

Changed the MAF to a two year old fresh RS2 one, made not difference. Electrical contact cleaner sprayed on MAF contacts.

New oem fuel filter fitted - no change.

When you go WOT, the car powers through the momentary hesitation to the red line, but the fault is annoying, and should not be there.

I know it could be anything such as one or a combination of two below, and so in no particular order;


1. Rubber boots - channel breaking down under the pressure of WOT
2. oem coils - channel breaking down under the pressure of WOT.
3. POS units - channel breaking down under the pressure of WOT.
4. Full pump - too old.
5. Bypass Valve - Too old.
6. N75 - tired.
7. Waste gate - stickiness.
8. Boost Leak - gut feeling says it isn't this.
9. Injectors - ran injection cleaner in a tank of petrol, no change ?
10. Throttle body switch ?
11. Lambda probe - not this as only happens on WOT ?
12. Fuel pressure regulator ?
13. Vacuum lines / connections ?
14. Knock sensors ?
15.
16.


While I have the above bits on other I5 cars that work fine, before I go swopping stuff around blindly, I was just wondering if anyone had any definite pointers to save me some grief and time.

I fully appreciate vag-com would be a good idea, but as mentioned no easy access.

Thanks for any BTDT feedback / constructive criticism.

[Vorsprung durch Technik]

Did you change the spark plugs yourself? In case not,just a simple check if you haven't already done so,take of the alloy top cover (4 allen bolts) that holds the coils and check the original wiring to see if it hasn't started to crack as had happened to my URS6. Once i changed that over with good my problem went away completely.

Having read your piece, i can't help but put 2 and 2 together.You mentioned the extreme low mileage of 43k.Your car wouldn't happen to be the beautiful Ragusa green saloon that sold only a few months ago over in Ireland would it?

Cheers Mark.

[UrS4boy]

Missing and Hesitation Diagnostic

Dave, Dave, Dave !!!
You need to leave your ego at the door.

Ha Ha. I have a *long* memory and now your post comes home to roost.

Sorry, I can't help you. I am too busy checking my ego at the door.

Oh wait,....

http://forums.quattroworld.com/s4s6/msgs/22611.phtml be sure to follow the hyperlinks there too.

I am such a sucker.

[bernsaudi]

I had allsorts of silly stuff like that for 3 years until i got rid of the oem coils and put coils on the same as the 034 set.

[UrS6 - IamS6]

Your car wouldn't happen to be the beautiful Ragusa green saloon that sold only a few months ago over in Ireland would it?

Yes.

[UrS6 - IamS6]

Ha Ha. I have a *long* memory and now your post comes home to roost.

Sorry, I can't help you. I am too busy checking my ego at the door.

Oh wait,....

http://forums.quattroworld.com/s4s6/msgs/22611.phtml be sure to follow the hyperlinks there too.

I am such a sucker.

Dave, I didn't expect you to forget, with your encyclopaedic knowledge,

but then again loads of other people on here, me included, don't forget either.

You're helpful and abrasive in equal measure, though sometimes the balance can tip too far one way on occasions.

I have double doors on my own garage to allow me to get my own ego in and out more easily.

But enough k*ob measuring, as Alex would say, and let's get back the the problem in hand, an I5 acting up.

Thanks very much for the link.

Kind regards.

[Vorsprung durch Technik]

It would be nice of you to show us some lovely photos of the car.Do you have any to post?

[UrS6 - IamS6]

It's used daily and is filty, but the engine bay is pretty much brochure like, and original.

When one is used to tattler UrS6 cars, e.g. rusty fuel pipes underneath the car etc., they are mint on this one.

It washes up very well though, and now has Mk 1 S8s, with 255/35/18.

Really needs to be lowered by about an inch. An item for later in 2015 if funds allow.

Agreed will get some decent photos in January 2015, and get another member to post them for me.

[UrS6 - IamS6]

Hope to be able to swop in some spare POS units tomorrow, and post the result.

Does vag-com show us this type of "mild" ignition problem as a code, or is it not able to "see" it ?

[Vorsprung durch Technik]

It sounds like the engine bay is really clean but then i am not surprised as its such a low mileage example.Good to hear your using it everyday must be great to be able too use it that much a bit like stepping back to 1997 and all the better now petrol prices are coming down.

I used to be like that about posting up pictures and even i managed it in the end after trying to work it out and scratching my head.If i can do it any one can.

All you need to do is click on the paperclip above when you go to post and up a page comes "upload file from your computer" that would be the photo. So you press upload and choose a photo from your computer/laptop then in the bottom right of that box it says in a little box upload.Press that and your photo will be loaded into the post.You then submit reply. I then go back to the post and open up the picture enlarge it and right click and copy the url.Then go to edit the post, put cursor where you want it then click on symbol/box directly below the paper clip but one to the right, looks like 2 mountain peeks. A box opens up and paste the url code in there that you copied then press ok and submit reply as normal. It all sounds long winded but it's easily done in 15 secs or so. Give it a try.

Good luck with it and i hope you manage to find the slight fly in the ointment in the rev range you mentioned and i look forward to some classy pictures of her in 2015.

All the best.Mark.

[UrS4boy]

Hope to be able to swop in some spare POS units tomorrow, and post the result. Does vag-com show us this type of "mild" ignition problem as a code, or is it not able to "see" it ?

Nope. None of the ignition components on an UrS (S2, UrS4/S6 or RS2) throw a direct code. Hence my diagnostic write-up.

Hesitation and hic-cups occuring under boost are most often the result of weak OE coils. At least on high mileage cars. With yours being so low mileage that could still be true but I would confirm the condition of your spark plugs and boots before changing anything else, i.e. POSs and certainly not coils.

YET.

[UrS6 - IamS6]

Changed POS, one at a time, no better, swooped in coils and boots complete, no better.

Swopped in a four year old oem bypass valve. Engine perfect, pulls perfectly every time all the time.

All my S6 car's bypass valves end in A, the four year old replacement one ends in B.

Don't feel it's significant, other than it works.

Going to order and fit an N S3 bypass valve in the New Year.

Really pleased as this had been going on for nearly two months,

I have to just replace front shocks, and definitely the two lower control arms.

Others should consider buying a Bosch "N" bypass valve if yours is not fresh, and the car is not pulling faultlessly to the red line.

Thanks.

[Vorsprung durch Technik]

Well that problem was found very quickly.Nice one!!

What front shocks are you going to go for? I have already purchased my new shocks and as far as i can see the best place to look for the lower arms is Germany on ebay. I would go for Lemforder as they seem to be the best quality available having read other S6 threads. What are your thoughts?

[UrS4boy]

Bypass (Diverter) Valve info

http://forums.quattroworld.com/s4s6/msgs/20994.phtml

[UrS6 - IamS6]

Well that problem was found very quickly. Nice one!!

Thank G*d. But from how nice the car pulls now, it had been going on for a good while. Only started properly swopping bits today. Other than changing to NGK about a month ago, and tightening all the boost hoses.

With these cars, it is certainly helpful to have a complete spares car(s), or certainly loads of "normal" :roll eyes: spares in stock ready to swop over to check for faults / to aid ease of quick replacement without having to wait while a new / second hand is bought.

I appreciate storage space for complete cars is an issue, but for daily driver it is almost a requisite.

Mentioned, really just for all newbies, or people thinking of buying a pre 97 S car.