audi a3 1.6 8v loses power & accelerator pedal judders???

hough

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Location
Poole, England
Car
VW T5 swb 2.5tdi
Hey can anyone on here please help, my other halfs car is playing up as one minute it will run fine the next well, the engine Seems to loss power and feels very jerky even the accelerator cable seems to judder under your feet and it really does judder, the car is fine when cold but plays up when warm iv had it checked and the maf is ok but i did replace the cat well by passed it as it was blocked with soot!!!
also the problem mainly seems to appear when the engine is warm and I forgot to say the revs do drop to about 500/400 rpm
Please help

Ps the Audi a3 is a mark 1 1.6 8 valve reg 2000
 
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hey and welcome. the cat being blocked with soot would be a worry on a petrol. maybe o2 sensor.
has the issue only came about since you deleted the cat?
coolant sensor could be the other issue. remember the wifes car was juddery as hell when it was playing up but it was easy to notice as the coolant was showing cold most of the time
 
The engine was worse before I removed the the cat!!! IV replaced the engine temp sensor yesterday and the engine still not right, its weird as when cold the engine is great but as soon as it starts to warm up the worse it gets, under load the engine feels so lifeless and the strange thing is when is rev the engine and release the pedal so the revs drop the revs will drop right below the 900rpm idle to about 400rpm and the accelerator pedal will sometimes judder and you can really see it, so do you thing an o2 sensor might be the prob as iv been to see 4 garages now and everyone has no answer????
 
for a start get vcds on it see if there are any codes stored on it.

whats the throttle body looking like? the idle v/v is part of the throttle body if its drive by wire - cant remember if the 8v are or if they are cabled - if its dirty it wont be helping
 
Well I checked the vacum pipes and all seems well, the throttle body was all black with a thick dusty grease but I believe is clean now. And the engine seems better but now it revs quite high and still has a mind of its own as it will rev now from 1100 to 1600 rpm even when warm, I was thinking may be its the maf but it was replaced about 3 months ago, all be it with a used one so I'm guess could the maf be playing up???

And the accelerator is cable operated :)
 
idle valve is what keeps the engine idlinlng. on DBW (Drive By Wire) engines its interoperated into the throttle body. on cable engines it will be a sperate valve.

could well be the MAF then if a used one has been fitted. had it been a DBW engine then after cleaning the MAF it could be re aligning the throttle body.
 
one garage I took the car too told me it might be the lambda sensor but could that affect the engine in this way?
 
yes it could be trying to ajust the fueling.

best bet would be to find a vw specialist that has access to vcds and can take the car out and log the sensors while its on the road. if they are good then they will be able to see if the maf is under or over reading as well as getting the information from the lamba sensor.
 
Well I replaced the coil pack and leads, also I gave the throttle body a bit of a clean as it had a black greasy like #!#!#!#! inside the car seems better as it now revs between 1000 and 1800 rpm but the revs are still up and down

I think the black grease stuff must be from where the breather pipe had broke and the garage told me they had cleaned the air intake system
 
yeah the black oily stuff is from the breather pipe. its part of the EGR setup. so your putting dirty exhaust gas back into your inlet to lower emmissions.

problem is as youve found out it makes the throttle body and the rest of the intake covered in gunk. if you were to remove most of the PCV setup (positive crankcase ventilation) youd find alot of the pipes will be full of gunk
 
I don't have a egr valve only a charcoal fuel filter but on the charcoal filter there seems to be an in and outlet on top and another pipe on the botto which connects to nothing unless its a breather pipe????

Also im gona remove and clean the throttle body and see if this helps :)
 
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well iv cleaned the throttle body but have noticed if I don't connect the electrics to the tb the engine runs nice but as soon as you connect the power ot runs like a bag of poo so could this be my idle sensor on the side of the tb so if so so you nice to replace the whole thing????
 
well I thought the car was sorted its not reving like mad now but the car started to run rough again and losses all power, im starting to give up
 
I found the problem, Well the problems it turned out my stepper valve on the throttle body was faultly, the crankshaft sensor was burnt out plus the maf had a fault to, I just can't believe they all went wrong at the same time, at least the other half happy as her car is working properly again :)
 
i thought the stepper motors were only on the electronic throttle bodies. you did think the MAF as well

glad its all sorted

and you will have an EGR setup unless youve removed it. the charcoal cannister is a waste of time as well. it collects the vapours from the fuel tank and adds them when needed into the intake. all in the name of emmissions
 

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