Passat 1.8t Throttle response

**tea drinker** · 19-06-2015,05:46 PM

Hi, I have an age old throttle response issue on the 1.8t, I have some time out from work so I might have a go at fixing it.
Car accelerates very hard on about 1/3rd throttle, whereas if I mash it it will accelerate less hard.
Sometimes like a carb engine I have to find the best accelerating spot on the pedal.

Down through the years it's got:
New pedal
New MAP sensor
New fuel pump
new Fuel pressure regulator.
I replaced those electrical change over valves under the manfold with a pair from the scrappie.
Nothing seems to make much difference.

If I do a reset of the engine by pulling the battery it seems better, but then it seems to learn worse.

As fas I can tell the wastegate actuator isn't leaking, and the wastegate itself seemed ok.
I haven't checked it's hold pressure or adjustment yet. Might try adjusting that....

I brought it to a chap that deals with Passats a lot... he had a similar issue on his own car he never resolved :-(
It's not chipped nor anything.

Any idea which VAGCOM measuring blocks to use to try and tie it down?

**SammoVWT** · 19-06-2015,07:26 PM

A general fault scan would do for a start - whatever it is, it gets worse after the settings are learned.

After experiencing hard to find faults with my own car, I would have similar symptoms of a reset - runs like a dream for 10 mins then back to the same old.

So after that bitter experience, it could well be something electrical. Do you have any rough idling etc?

Does this occur after the car has warmed up? It would be interesting to see what your rear O2 sensor reading is doing. Because it might not be at fault but your converter could be faulty - which then has a negative effect on your sensors and resulting power after it comes out of its safe pattern and tries to regulate on learned values and o2 readings etc.

Educated guess due to the components that have been replaced, which I would assume are fault related and hence fuelling issues and general richness of operation at times. Plus the age of the vehicle taking that into account too.

Short of that a throttle body alignment might not go amiss. When was the last time you gave the vacuum system a check over?

**tea drinker** · 22-06-2015,10:55 PM

Hi, yeah I went over the vacuum system last night, a few loose hoseclips got tightened. However.... problem remains.
I changed the throttle body for a spare one I picked up some time back.... no improvement.
There's no codes.
BTW I done that throttle pedal adaption - the one where you floor the pedal for 15 seconds with ignition turned on. That seemed to add some immediacy to the pedal.
I'm running dipetaine through it now, it should be bit cleaner after that. Still coming up with a blank on the cause.

**zollaf** · 22-06-2015,10:59 PM

no power, no codes, might well be the AMM

**tea drinker** · 22-06-2015,11:12 PM

AMM zollaf?
It's not too bad on power - just it is much more powerful on 1/3rd throttle than full. I'm wondering if it could be pulling timing or something?
Feels like "wrong" control of turbo, if I had to guess.

**zollaf** · 22-06-2015,11:13 PM

air mass meter, also known as maf..

**calum** · 02-07-2015,03:58 PM

You still have this problem? I remember replying to this years ago, lol . Check the vacuum hoses to the n249 under the inlet manifold, this allows the ecu to control how much boost you get and how long it holds it for, any leaks in that could cause problems. Also check for any air leaks in the turbo inlet pipe, if it's not seated at the airbox properly can cause problems. The n249 can be bypassed if you connect the hose that runs to the n249 directly to the inlet manifold, you must put the hose you removed from the inlet onto the n249 valve, this is for testing purposes only, turbo damage could occur if you leave it like that. Expectations- boosts much quicker, better throttle response and it will boost as long as you hold the throttle down, I hope this gives you a few ideas to work on, good luck.