Strange idle connected exhaust vibration

[220bhp]

Today I tested the resistance between pins 30 and 45 with the engine cold and got 2880 ohms, so the new sensor and plug are all working as they should.yester day I used the car for a 50mile trip and it ran well from cold,but as it warmed up it started to get jerky again below 2000revs and at 1450 there is still a flat spot where it feals as if the throttle pedal is not controling anything,then it jerks and the revs rise as normal ,and the drone returns at 2000,but after that the car runs prity near perfectly.boosts well and holds,with no problems.
Ihave just disconnected the temperature sensor as Newsh suggested and It did not run very well when hot at any revs.
So I am sure the car had more than one issue at the start and that some of them have been cured by replaceing the leads and the temperature sensor etc, but the car hard work to drive at low revs,it still idles at 1050,
it still ocilates at 1450 and there is still this drone at 2000.
I feal like a blind at a brothel,I know its there but I cant find it,very frustrateing.

[Carfreak]

Today I tested the resistance between pins 30 and 45 with the engine cold and got 2880 ohms, so the new sensor and plug are all working as they should.yester day I used the car for a 50mile trip and it ran well from cold,but as it warmed up it started to get jerky again below 2000revs and at 1450 there is still a flat spot where it feals as if the throttle pedal is not controling anything,then it jerks and the revs rise as normal ,and the drone returns at 2000,but after that the car runs prity near perfectly.boosts well and holds,with no problems.
Ihave just disconnected the temperature sensor as Newsh suggested and It did not run very well when hot at any revs.
So I am sure the car had more than one issue at the start and that some of them have been cured by replaceing the leads and the temperature sensor etc, but the car hard work to drive at low revs,it still idles at 1050,
it still ocilates at 1450 and there is still this drone at 2000.
I feal like a blind at a brothel,I know its there but I cant find it,very frustrateing.

Same problem as I had.. replaced the TPS and the throttlebody cause it was jamming. Try to readjust the tps fully anti clockwise and rev the car! Also try to disconnect the multi temp sender!

[220bhp]

Thanks mate,butI have changed both the throttle body and TPS.adjusted it several times with no change,also tried it with the MFts unpluged.

[Carfreak]

Thanks mate,butI have changed both the throttle body and TPS.adjusted it several times with no change,also tried it with the MFts unpluged.

okey This problem must be a real pain in the ***.. Have u done a output test in vag-com and looked at all the blocks ?

Have u checked the knock detectors, timing(marks at crank, cams, flywheel and disty) and how ur cam knocks looks like ?

One more thing that comes to my mind is the little metal thing on the flywheel, maybe it´s a little off center or something ?

Done a comp test and a leakdown test ?

[220bhp]

I have done all those things accept the leakdown test and compression test.the engine has just been rebuilt with new pistons,rods rebored etc, done about 2000miles,so should be OK.
Knock sensors are new.

[twoqu]

Lou,
We still need to work out whether the ISV is actually controlling the idle somehow. Of course it may well be a coincidence that disconnecting the ISV on Johns car duplicates most of the symptoms!
I can't remember whether we tried flicking the A/C switch which under normal circumstances would cause an increase in idle speed. I don't think even with it on it would cause a 1050rpm idle, but it certaintly does boost it from 830rpm.
I know all the A/C mechanics have gone but electrically it should be hooked up. Try it and see what happens.
The only other thing I was thinking was to somehow make a manually adjustable ISV that would allow the setting of an acceptable idle speed temporarily. If we could set the idle to @800rpm manually it would confirm to us that its the ISV that causing the high idle.
As the car drives ok we can rule out a limp home mode. That still leaves the N75 plumbing. I know you tried blocking before and it made no difference but I am wondering if the ecu is clever enough to factor that in and adapt to it. Perhaps we should have tried blocking it off and pulling the ecu fuses so that it starts its adaption again when restarting.
Unfortunately we don't know enough about the ISV's behaviour. Without power it uses the bypass channel. We know from John's car that gives us a 1050rpm idle. However we don't know how much idle it can go to when powered up. I would have thought that with the A/C signal on that would be near the top limit but as I recall that only bumps the idle up into the 900rpm range. Cold starts also bump it up and it then decreases as the engine gets warmer. As yours does not sem to change hot or cold it sounds like its not being controlled even though as far as we can tell it has the ECU connection and power! Perhaps cause the idle is artifically high the ISV control is not being performed as the ECU has reached some threshold. That MG thread implied that the ISV is still powered up to 2000rpm which sort of rules that out. If it has duty cycle on it then it must be moved from the bottom stop position.

I don't suppose that new MM you have has got a duty cycle capacity has it?
That might just gives as a clue as to what if anything is happening at the ISV. In an idel world you would have had a PC scope at your disposal but its an expensive thing to have laying around just for one issue!

[220bhp]

Robin,I had another go at adjusting the TPS today,and I have managed to get the idle down to 950,but it still hunts at 1450 and there is still this fealing that it is unhappy till the revs rise above 2000. it will however run in forth gear at 1000+ with your foot of the throttle,but when you press the throttle it hesitates like there is no connection ,then lurches forward,very strange.however above these revs it runs well.
I feal that haveing done almost all I can ,that there must be a vacuume leak that I cannot trace,but how do I test the vacuume system above and beyond the normal boost leak test.

[Carfreak]

Robin,I had another go at adjusting the TPS today,and I have managed to get the idle down to 950,but it still hunts at 1450 and there is still this fealing that it is unhappy till the revs rise above 2000. it will however run in forth gear at 1000+ with your foot of the throttle,but when you press the throttle it hesitates like there is no connection ,then lurches forward,very strange.however above these revs it runs well.
I feal that haveing done almost all I can ,that there must be a vacuume leak that I cannot trace,but how do I test the vacuume system above and beyond the normal boost leak test.

I had exacly these symptoms.. adjusted the tps max anti clockwise and the problems is gone I have no vacuum leaks or anything like that either!

[220bhp]

I had exacly these symptoms.. adjusted the tps max anti clockwise and the problems is gone I have no vacuum leaks or anything like that either!

I take it you mean clockwise from the front of the car.As when I tried this today I noticed that if I moved it to the stop it opened the throttle by a small amount.It was very difficult to adjust it so the throttle did not move,and get it to click on of.

[twoqu]

Well 950rpm is closer to idle speed + A/C boost!
The question is why by adjusting the TPS it's dropped a 100rpm!
Think I mentioned previously that the throttle body might not be shutting fully. If it was open more than it should then that would render the ISV useless as that is supposed to regulate the airflow into the engine at idle speeds. The engine will just suck in the air through the throttle plate whilst the ISV tries in vain to control it.
So it might not be a leak as such but an orrifice that needs to be closed more!

[Carfreak]

I take it you mean clockwise from the front of the car.As when I tried this today I noticed that if I moved it to the stop it opened the throttle by a small amount.It was very difficult to adjust it so the throttle did not move,and get it to click on of.

Yeah ur right.. I adjusted it so the throttle opened a bit - maybe it´s the wrong way of adjusting it but all my problems is gone after that


Is there any guide with pics on how to adjust it propperly ? Saw the guide on Quattroforum but that ain´t much of help Alot of the audi owner says that u adjust it till it clicks when u open the throttle - when adjusting it like that it revs like an old 4-cyl volvo or something till it goes over 2000rpm..

[220bhp]

Robin, as I said earlier,I only noticed today,that by moving the TPS to its stop,in a clockwise direction,from the front of he ca,r it opened the throttle a little,but to get it to click, on of,it is very hard,as when you do the screw up it moves it a little.
I think the only way to set it up is with the the throttle body of the car.It may be better to replace the screws with bolts, and use a small socket instead of a dumpy screw driver.

[twoqu]

Just wondering if its worth the trouble to remove the TPS from the TB but leaving it connected electrically. That way if we get the correct idle we have managed to identify the problem. Obviously you would have to set it up again!
Not sure whether it seals the spindle from that side though.
The only way the idle could have dropped is that the throttle plate was shut further. The idle switch is just that, its either on or off.

[twoqu]

Perhaps you are being a bit heavy handed. Basically all we need is for the idle switch to close with the throttle shut. I have experimented with an ABY TB. It does not take a lot of force to close the switch. In fact the spring tension on the TB keeps the TB plate shut. If you force the TPS right against its stops on its bracket you can as you say open the throttle plate.
To prevent the TB plate moving you can either wedge something against the throttle stop part of the bracket, the metal L bit at the bottom beneath the linkage, or get someone to hold it against the stop. Do not try and wedge the plastic part of the linkage!

[Carfreak]

Played around with my TPS yesterday.. I´m 100% shure that the tps has nothing to do with ur problems! I think u should check ur timing once again! Another thing that came to my mind is to fit a new earth cable between chassi and valve cover!