Help Please flat spots & rough power delivery

[Land_Raver]

Hi all,

My 1.8T AGU engine has developed a random flat spot & poor idling usually after I have pushed the car heavily on the turbo for a few miles. This usually clears when the engine is cooler?

Have fixed the air leak on the Secondary Air Pump casing, replaced the spark plugs, replaced the boost valve & replaced the coolant temperature sensor which has eliminated most of the poor running.

The car has been re-mapped (unknown map) & is running 200HP (Rolling road dyno) with no engine management lights on. Engine has covered 60K with full service history.

Was wondering if it was the air flow meter or air temperature sensor that was at fault & if it was then why there is no fault code?

Any help or suggestions would be greatly appreciated!

[KenONeill]

Has this been more of an issue in the last week or 2? If so, then I think you've got a fuel temperature problem.

Easy test for the MAF is to disconnect it. If the engine runs better with the MAF disconnected, then replace the MAF.

[Land_Raver]

Originally Posted by KenONeill

Has this been more of an issue in the last week or 2? If so, then I think you've got a fuel temperature problem.

Easy test for the MAF is to disconnect it. If the engine runs better with the MAF disconnected, then replace the MAF.

Thanks

The fault has been more so the last couple of weeks although has been like it for a while. Will try disconnecting the MAF.

Surely though the engine will not run with MAF disconnected??

[KenONeill]

If it's got bad signals from the MAF, it tries to use them, and runs badly. When you disconnect the MAF it uses a set of default settings.

[Land_Raver]

Will try that out on the way home from work

[Land_Raver]

Originally Posted by KenONeill

If it's got bad signals from the MAF, it tries to use them, and runs badly. When you disconnect the MAF it uses a set of default settings.

Many Thanks for the info Ken, the car runs better with the MAF disconnected although will clear the codes for ASR & Engine management (as the check lights are now on) Will get a brand new MAF.

Top Bloke

[Land_Raver]

Have replaced the MAF with a replacement one from a Skoda Dealer £20 surcharge on old unit so guess thate these are reconditioned. The Parts man said that faults with these are common across the whole VAG range.

Engine ran really badly on initial installation coughing sluttering & backfiring with no base idle Revved the engine throuhout the rev range 1K for a few seconds then 2K up to 5K then it was fine. Guess that the Engine Management system has to learn & recalibrate when a new MAF is fitted!

Things are great again

Many thanks again Ken for your advice also Briskoda & everone that uses it what a great resource

[Lloyd55vrs]

dam mafs, ive heard they break all the time whenever they feel like it

[Land_Raver]

Originally Posted by Lloyd55vrs

dam mafs, ive heard they break all the time whenever they feel like it

Yes completely random my last car was a 97 A3 1.8T sport AGU engine 43K & had no Engine management faults in the 3 years I owned it!

[vrscoz]

being a bit dim here which is the maf sensor on the 18 T

[Taxi 219]

The MAF sensor is immediately after the air filter housing and has a multi plug on it.