Strange idle connected exhaust vibration

[220bhp]

Since I replaced my rebuilt engine in my rs2'ed 3b coupe,I have had issues with it,one of which is the undrivability at low revs,its jerky,and the throttle is not smooth.I have done the usual and cleaned the ISV,changed the TPS,checked for vacume leaks and changed all the pipes,but it was still the same,idle at 1200 and jerky,boost osilating after bar.
The other thing is the boom from the 3inch exhaust when running at low revs has been unbairable,to the point of thinking of replaceing it.
But hears the strange thing,I had one more go at ajusting the throttle as Jon441 noticed that the arm was loose,this made a big differance in the drivability of the car,and a bit of an inprovment in the way the car boosts,but most of all the boom from the exhaust has gone.
I have no idea why this change in the exhaust should happened,or what was causing the vibration and boom,before it was realy bad and te car seemed to be holding back till you hit the gas.

[QuattroFever]

TPS is clicking too early maybe? So ecu thinks it's closed throttle when at ~3-4% throttle instead of 0% so at 1200rpm it will be messing with ignition and isv to compensate making it drive like crap within that band. If you have an air leak will make this even worse.
Boost oscillating and drone - again, air leak or try cleaning n75 and check wiring and wastegate bolts/gaskets?

Have you checked the plugs are tight. They can work loose sometimes losing a little compression in a cylinder. Don't go mad tightening them though they will strip pretty easy

[220bhp]

TPS is clicking too early maybe? So ecu thinks it's closed throttle when at ~3-4% throttle instead of 0% so at 1200rpm it will be messing with ignition and isv to compensate making it drive like crap within that band. If you have an air leak will make this even worse.
Boost oscillating and drone - again, air leak or try cleaning n75 and check wiring and wastegate bolts/gaskets?

Have you checked the plugs are tight. They can work loose sometimes losing a little compression in a cylinder. Don't go mad tightening them though they will strip pretty easy

I have checked the plugs,and for air leaks,what you say makes sence I can hear the click but it is imediate
The car is running better than ever at ATM but it is still not right.I will check wastegate and n75,the gaskets are new as is the n75 wireing.What do you clean the n75 with wd40.
I have another 3b ECU that is unopened,I am going to try to fit it with standard injectors and fpr to see if it boosts and runs any better,just to rule out any possible problems with my ECU,it was mapped on the blown engine by MRC and they could not get it to make power even running good boost.Minea said it was possibly the cams,which are now changed or a fault in the ECU,so I need to check it out before I have the map done again

[QuattroFever]

I'd give a blast with carb cleaner first then give a good washing through with wd.

Have you pulled the codes to see if its moaning about anything?

[220bhp]

Yep, done that with th help of Newsh, codes as follows,
00533

00525

00513
All have been addressed,including replaceing all the injector seals on the IM,a boost leak test which found a leak on the intercooler,now fixed with mark h mod plus,replacement of all vac lines.
My main consern is I have no idea how the old map will effect the car after lowering the compression and the introduction of a 7a ex cam,apart from the fact that the engine has been balanced and the engine components are all new
I have spoken to Doug at MRC and he says the issues are nothing to do with the map,and that it is down to a mechanical issue with the car, but at the same time they could not tell me what is the cause, and that I should fix any problems before I bring the car to them for a remap, catch 22.

[twoqu]

Lou,
Firstly can you hear/feel the ISV working? If not check Fuse 24 I think.
Just because you can hear the TPS click, does not mean that its functioning ok! Peel back the rubber boot from the rear of the conector and measure the resistance between pins 4 & 6. It should be 0 ohms. If not the ecu does not know the throttle is shut and there will be no idle stabilisation. You could try bridging those terminals (at idle only) and if the idle goes back to normal then at least you know the circuitary and components are ok. That would leave the TPS. The limp home idle is 1100-1200 which might be indicative of something.
Does the car have aircon by the way?

[prj]

Put stock injectors, stock ECU, stock FPR on it, then troubleshoot.

[220bhp]

Lou,
Firstly can you hear/feel the ISV working? If not check Fuse 24 I think.
Just because you can hear the TPS click, does not mean that its functioning ok! Peel back the rubber boot from the rear of the conector and measure the resistance between pins 4 & 6. It should be 0 ohms. If not the ecu does not know the throttle is shut and there will be no idle stabilisation. You could try bridging those terminals (at idle only) and if the idle goes back to normal then at least you know the circuitary and components are ok. That would leave the TPS. The limp home idle is 1100-1200 which might be indicative of something.
Does the car have aircon by the way?

Thanks Robin I will recheck as you say, With regards to aircon,the car did have aircon,but I have not reconected it.

[220bhp]

Put stock injectors, stock ECU, stock FPR on it, then troubleshoot.

I intend to try and do just that today.could the mods I have cause any issues to a standard ecu/injector/fpr setup,these include rs2 turbo and exhaust manifold, wagner intercooler 044 pump 7a ex cam,lower CR.

[220bhp]

Had no chance to work on the car,due to work raiseing its ugly head on a sunday,the pleasures of being self employed I gess.
Work is just crazy at the moment,but I will try and find the time to test all the things suggested,in the mean time thanks fr all the help

[220bhp]

Found some time to work on the coupe today.I wanted to change the ECU,and the injectors,plus the FPR,in order to rule out the ECU from my cars running problems
Guess what,I cannot find the standard injectors,so that ruled that out.
So I desided to change the throttle body and the TPS.this resulted in no change.
The car is behaving strangely at around 1800 to 2200 revs. you can feal the car grumbling,and it is not pleasent to drive at low speed. .
I have cleaned the ISV.and as far as I know it is working fine.At times the car will boost well,but other times it will stumble.
But then when it is hot ,the exhaust will start the drone again at low revs,and believe me the ressonance is unbearable.
I will hunt out the injectors and check the new parts out as soon as I can, but right now I am getting very fed up with this bloody car

[prj]

So you have not gotten anything done
Pull codes again, that oxygen sensor: signal too low code probably means that your O2 sensor is dead.

Also, I would not recommend driving and flooring it around like that, unless you are looking for another engine...
It stumbling might be meaning that it is going lean and knocking.

[newsh]

I have a set of 3B injectors Lou, if you need to borrow them I can stick them in the post.

Just a thought, the drone when hot may be the exhaust expanding and touching something, the body or the subframe. Stainless expands a lot, the Miltek on the avant used to expand and touch the rear bumper, it was easily an inch away when cold.

Have you leak tested again yet since fitting the MarkH mod? Will it hold 1 Bar now? Its a shame it took all our time to replace the injector seals the other week, I'm sure we could have got further with a bit more time.

[220bhp]

THanks for that John,but I did find them last night,and yes I did presure test it after the mark h mod and it was good,but I changed the throttle body and the TPS yesterday so I will have to check it again.
I take on board what you say about the exhaust exspanding,and I thought that was the cause,but now I am not to sure.I did some more adjustment to the TPS and for a day or two it seemed to cured both the drone and poor slow running issues and it was drivable in traffic ect, but then it came back,and I havent managed to set the new one successfully
I need to get vagcom so I can pull the codes,as for some unkown reason they wont blink.

PRJ. thank you for the warning,the stumbling that I get is not harsh its just like the ecu cant make up its mind what to do at around 1800 revs and you cant drive it at those revs without these issues,as the revs rise the car gets progressivly smoother and the drone go's away,I have had a knock sensor failiur in the past,but this dose not fell like that.I have no idea what to exspect when I change the ecu ect, but I will find the time somehow this week,I just wish ther was someone around hear that I could pay to do it,as finding time of work at the moment is almost impossible,but where I live there is no one with those skills,very frustrating.

[twoqu]

Lou,
Was it always like this or has it detiorated. I think I read one one of the threads that it got progressively worse.
If you bridged the TPS, that should have forced an idle condition. Of course it does not eliminate either an unmetered air leak or indeed broken wiring between either the TPS or the ISV. Again its something to test rather than assume it ok!