Hesitation and Can I believe this Rolling Road Figure?

Hi Al

Did u take the brake servo hose off and inspect it?

Are u still using the forge 007 DV?

The problems u are having sound exactly what happened to my car, both Star performance and QST told me there was nothing wrong. The so called experts don't know /ubbthreads/images/graemlins/swear.gif.

If you still have the forge DV try and get a AMD viper, even if u borrow it. I found the forge valve to be useless.
 
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There was a lot of talk on the Volvo website about EXACTLY this type of missfire, eventually they solved it by fitting a new lambda sensor, the "theory" behind this was that the lambda was out of spec causing the ECU to have trouble in believing the difference between the signals from MAF/throttle position and lambda, I would be tempted to try a new lambda


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Interesting...
But lambda is only of use in closed loop mode below about 2500RPM due to the narrow operating band of the VAG lambda sensors...or so I believe.






ECU closed loop control operates where the lambda can measure the mixture over a fairly small range - hence idle to approx 2500RPM.

I had a lambda sensor go bad on my golf GTI and idle was bad, town driving was rough and MPG was awful, but above 2500 it was perfect and made perfect power on the rollers with no hesitation above the open loop changeover point.

As far as I know, the S3 also only uses lambda in closed loop mode below approx 2500RPM although ther second lambda sensor IS used to bring in a check light and possible 'limp' mode if the post cat measurement goes way out of spec...but again, I believe this to be a narrow band type that is set to measure post-cat differences in mixture that happen to be within it's narrow band of measurement.

Hence, I can't see the lambda sensor causing a missfire like hesitation at 4000+ RPM...I may be wrong though.

Lambda is easy to map with VAG-Com, so it shouldn't be too hard to spot irregularities.

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Didn't he say part throttle 2002-2500rpm though?
i'm not sure, I know I fiddled with a Porsche one a while back on a C2Turbo, that dropped from closed loop at 3200rpm, or a full throttle signal, I would have thought more modern engine management system would be staying in closed loop longer, but I don't know to be honest, nice trick with the lemon! I may well try some citric acid on my Volvo one as that's got the surges at the moment--a sure sign the Lambda's response has been sheilded with exhaust stuff.
 
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Didn't he say part throttle 2002-2500rpm though?


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Quite possible...I was rushing and couldn't find the original revs problem...

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i'm not sure, I know I fiddled with a Porsche one a while back on a C2Turbo, that dropped from closed loop at 3200rpm, or a full throttle signal, I would have thought more modern engine management system would be staying in closed loop longer, but I don't know to be honest,


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Ahh...but many Porsches use Bosch wide-band lambdas as standard with their own management system...many of the lambdas you buy for wideband kits are standard 911 parts...so this is perhaps not a straight comparison.
The VAG lambdas are not wideband...
 
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Hi Al

Did u take the brake servo hose off and inspect it?

Are u still using the forge 007 DV?

The problems u are having sound exactly what happened to my car, both Star performance and QST told me there was nothing wrong. The so called experts don't know /ubbthreads/images/graemlins/swear.gif.

If you still have the forge DV try and get a AMD viper, even if u borrow it. I found the forge valve to be useless.

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Hi Andy,

I partially removed the brake servo hose from the end of the intake manifold. Which gave enough movement to look at the "U" bend section of pipe. It looked fine.

What I couldn't do was remove disconnect all the hoses. I removed all the clips, but the hoses just would not budge. Got any tips?

Yeah. Still using the forge 007. Anyone out there with an AmD Viper that I could try?

Cheers

AL

PS: Thanks to everyone for the continuing help on this.
 
Hi Al

The u bend hose is connected to another hose above it, i just cut the solid bit of rubber that connects then to fully remove it.

U could borrow my viper DV but i think im a bit to far away.
 
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If you still have the forge DV try and get a AMD viper, even if u borrow it. I found the forge valve to be useless.

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Let's be honest...one DV is as good as the next in performance terms...
The AmD Viper is no better than the Forge when both are clean, undamaged and new.

I personally found the AmD DV to last longer without re-builds...but that's just me.

Strip and clean the Forge valve carefully, coat it in hi-temp grease and re-assemble.
It'll be fine...

Any hesitation on-off throttle I ever had was resolved by doing this...it's just that the time between re-builds was longer with the AmD viper!

Even re-locating the DV to the cold side - after an uprated SMIC and decent sized FMIC - wasn't enough to prevent it from sticking occasionally...so it has to be done. And when you have to re-build now and then...neither one is any better than the other.

Again, just my observation...
 
[ QUOTE ]
Let's be honest...one DV is as good as the next in performance terms...
The AmD Viper is no better than the Forge when both are clean, undamaged and new.


[/ QUOTE ]

I think your missing the point. There no question that when both valves are operating correctly theres no differance in performance. The problem is the forge vavle dosn't operate correctly for long enough to compare them, when paying £100 for a DV you expect it to be reliable.

I had all kind of problems with forge valve. Forge were kind enough to supply me with a refurbishment kit free of charge. It lasted ONE DAY before hesitation returned.

Installed AMD Viper about 8 months ago and have not had to touch it.

I'm sure i can recall a post of yours saying that you had a problem with the forge valve?
 
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I'm sure i can recall a post of yours saying that you had a problem with the forge valve?

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I did...
I had to re-build it every 4 months or so...

But the AmD valve only lasted 5 months or so before re-builds...so not an entirely satisfactory solution, i'm sure you'll agree.

Although...some cars do seem to prefer different DVs.
 
Al, have you swapped the coil packs recently?

I had a proper hesitation on full throttle and changed all the usual suspects, cleaned the DV etc etc and a swap of coil packs solved the problem.

/ubbthreads/images/graemlins/smile.gif
 
Hi David,

No I haven't changed the coil packs recently. They were last changed in feb-03, for the "L" versions.

I'll add it to my list of things to check. /ubbthreads/images/graemlins/smile.gif

AL
 
Update...

Had the car down at AmD yesterday. Was good to meet Ed, Adam and Shaun. Excellent waiting room facilities down there now. The day went quickly actually, and numerous free coffee's was had.

The car. Well, typically, it didn't want to do the hesitation when the guys drove it. I took them out in it, and again, it just didn't want to play ball.

Although before they took the car out, they did do a basic settings reset and TBA, which may have affected things. But the car had been pretty well behaved on my drive down there anyway, no 100% hesitation instances....I guess it was just one of those days.

Anyway, on their test drive, they did spot an intermittent "Brake light switch" implausible signal error code. Why my VAG com did not pick this up is anyones guess.

The guys are pretty confident that the "brake light switch" will be the cause of the hesitation. The faulty switch was intermittently telling the ECU that the brake was being pressed. When the brake is pressed the ECU obviously receives this signal, and probably does something with the fuelling, probably for emmissions purposes.

If you look in the Electronic Power Control section of the Motronic injection and ignition system manual ( available from Erwin) it shows that inputs to EPC, amongst other things, are throttle position sensor, brake light switch, brake pedal switch and clutch pedal switch.

So the brake light switch could have an effect. So the guys at AmD may be right, only time will tell.

First impressions...car feels strong, and not one bit of hesitation on the way home.

But I'm not counting my chickens yet, the fact that the car has run well, on just one day, does not mean it will be running great tomorrow or in a weeks time. So I'll keep you posted.

Cheers

AL
 
I thought that if you brake when in gear, the ECU cuts fuel delivery to the engine, to assist with braking.
If it's doing this on and off then I could definitely see that causing hesitation?
 
BK

I think you are probably right.

Just spotted this on page 144 of the manual mentioned above...

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Command from accelerator pedal sender (potentiometer) to engine control unit for opening throttle valve is suppressed for safety reasons when brake is pressed. For this purpose, the control unit requires signals from both the brake light switch and the brake pedal switch.

If the brakes are actuated when the accelerator pedal is held at a constant position, the engine speed is immediately reduced to idling speed. Incorrectly adjusted switches may lead to unwanted regulating actions.

[/ QUOTE ]


AL
 
Well if that is the reason then fair play to AmD! Hope thats the problem...

It does sort of make sense mind you. If you sit and rev the car and press the brake pedal the revs fall..
 
I have probably tempted fate by posting this, and it will happen again on the way home. That would be my luck.

I should say, when this hesitation occured for me, the revs didn't fall, they continued to climb, possibly at a slower rate to normal, but the car wasn't pushing forward like it should. It was like the car wasn't boosting. But then all of a sudden, it would start again, as if the power had been cut and then switched back on again.

Anyway, fingers crossed.
 
indeed Al, you've been through everything else. Its about time you got is sorted for your own sanity (and pocket)
 
Seriously Al if you want it fixed take it too Jabba and get mike to have a look if he can't fix it you've got no chance.Oh and get a remap while your there.
 
Hey Al, this is EXACTLY what's been happening to mine (Although my brake switch was replaced once before, just not for this problem) so please keep us up to date /ubbthreads/images/graemlins/crazy.gif

Thx dude /ubbthreads/images/graemlins/beerchug.gif
 
Dicky,

3 days post-AmD, and no sign of hesitation yet! Car feels perfect.

But like I said to AmD, it's felt fine before, after a "basic settings" reset and "throttle adaptation"....so, I'm being cautious.

But at the moment I very happy. /ubbthreads/images/graemlins/laugh.gif

AL
 
Sounds familiar /ubbthreads/images/graemlins/crazy.gif Car feels great until you think it's fixed, THEN the hesitation comes back /ubbthreads/images/graemlins/frown.gif

I hope it's finally fixed for ya Al /ubbthreads/images/graemlins/ok.gif

/ubbthreads/images/graemlins/beerchug.gif
 
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glad to hear you've sorted it AL - must meet up with you soon!

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I know it's been a long time. Let me know when you are next up north. Come round for a brew.

AL
 
Well my cautiousness in not wanting to tempt fate has failed.

Almost 3 weeks (actually about 2 weeks of driving the car) since visiting AmD, yesterday and today the hesitation has occurred again. /ubbthreads/images/graemlins/burningmad.gif I just don't believe it...well...I do, been here before a number of times.

What on earth could it be?!

Think I might...

1) Change the MAF as a precaution
2) Change clutch pedal switch, following same theory of it being an input to EPC
3) Maybe change coil packs around perhaps
4) Maybe check O2 sensors again
5) If it still does it then, surely its got to be throttle position sensor/switch and throttle body.

Are there many more sensors and switches left to replace?!!!

AL
 
Oh that sucks. The brake light switch seemed to make sense too.

I was thinking throttle potentiometer too.

Would a MAF cause hesitation? I would have thought that the under-reading of airflow would be fairly constant, and that it wouldn't cause a power notch at any particular point?
 
A dodgy MAF gave me some pretty nasty flatspots, and power was down considerably...
 
furry **** ( http://www.m-w.com/mw/art/****.gif )
 
I so sorry Al, after all that I really hoped it was all sorted now /ubbthreads/images/graemlins/frown.gif
 
In case it helps, I just read this on a Skoda site:

Subject: "Turbo hesitation - now gone":

Just thought I would share with you that I am no longer seeing this on my car. I had a engine fault light come on last week, the diagnosis was a hole in the intercooler pipe. Thats been replaced with a throttle body clean and also a new overrun valve. one of the 3 must have cleared the hesitation, the car is now lovely and smooth across the whole boost range.
 
My car had bad hesitation when the Tb was on the way out.
 
Hi Al,is links in macc still trying to sort this for you or have they given up? If your car is still under warranty why not try a different dealer that someone from here can recommend. Get a fresh pair of eyes to look into it.

Must be a nightmare trying to sort this out.
 
Hi MO,

I have exhausted the Links Audi route. The last time they were able to reproduce the problem, they were stumped. When I had the car back with them for the service (before my visits to Awesome and AmD) they couldn't even reproduce the problem. So I have given up with them as far as this problem is concerned.

I do have Warranty (via Mondial) but, investigation work has to be paid for, if no problem is found with the car. They are a lot more strict these days, and with Huw now gone. /ubbthreads/images/graemlins/frown.gif

All,

For the whole of last week, hesitation didn't occur. So now it's even more intermittant before.

I'm off down to Warwick tomorrow, so I'll see how the car performs on a hot motorway run.

Cheers

AL

PS: The thing thats stopping me getting a new MAF is the fact that I don't know where to get the 5-point torx plus tamperproof (TP25) bit. Anyone know of a supplier?
 
I bought a set of security torx bits (and a myriad of other bits I had never seen before) as one set from my local A.R.E. It was about 10 quid, and the bonus is that I can use them with a flexible srewdriver to get access to most places. Made more sense than buying individual one-piece security torx thingies.

It was like this:
http://www.kwtool.com/catalog/images/starbitset.jpg

Maplins sell it:
http://www.maplin.co.uk/Module.aspx?ModuleNo=11520&doy=12m12

Or even just the bits you want:
http://www.maplin.co.uk/Module.aspx?ModuleNo=3800&doy=12m12
 
True. Torx are handy if you intend to try cleaning it, etc, but yes, MAF should have whole housing, even when done on exchange.
 
Cheers BK. I have that 33-piece set from Maplin. But it contains 6-point torx, and not 5-point. /ubbthreads/images/graemlins/frown.gif

Newer MAF's use the 5-point star torx.
 
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True. Torx are handy if you intend to try cleaning it, etc, but yes, MAF should have whole housing, even when done on exchange.

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Ahhh, I didn't know that they supplied the whole housing. From what I'd read on different sites, it sounded like just the sensor was supplied. That makes things alot easier.

Thanks guys.

AL
 
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Newer MAF's use the 5-point star torx.

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yup, tamper-proof torx, theyre a ******, and expensive too. Halfrauds can get them special order though.
 
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