flatspots on 1.8 20v(non-turbo)

[piston_slap]

Please help...

My car is a 1999 1.8 20V non-turbo....

When my car is cold it runs perfect but as soon as it warms up i experience a lots of flatspots most notibly at about 4K - 5K revs...

Does anyone know about this problem

Any help advice will be greatly appreciated.

[kniterider]

got the same car but not the same probs!, check you air filter is clogged with crap if it is clean it or get a new one, also whilst in ya air box check the MAF sensor its on the pipe from the air box to the plenum chamber, these can play up and cause engines to run all over the place, other than that if ya know any one with a laptop and the vag-com lead and software get them to plug it in and see what error codes it may be throwing up? (getting the lead and software as soon as my new laptop arrives!), run the fuel low, then put some optimax in and give its a good thrashing for 10miles, mine runs so much sweeter with this in, if i go back to normal unleaded the car feels a bit flat!

hope there may be a bit of useful info in this reply somewhere..

[piston_slap]

Hi Guys,

Just to let u all know that I sorted the problem.....

There is a temp sensor which sits on the thermostat housing. This sensor sends signals to the ECU......this sensor was faulty and was sending incorrect data which resulted in poor running of the car.

The sensor costs approx ?20 and took me about 5 mins to switch with the old one.....

The car now runs 100% better....PHEW!!!!

[kniterider]

nice cheap fix that one! will remember that 1 as most poor running probs are mostly caused by the dodgey MAF sensor!, just as a matter of interest how did you find out it was the temp sensor?, did you get some 1 to check with vag-com?

[piston_slap]

I spoke to a service manager who knew his stuff......

Told him the symptons and he said that it looked more than likely temp sensor...since it was cheap and easy to install i gave it a try...

[rickardo]

Now lads,

Think my GTi has develpoed a similar problem.  Its also a 1.8 (non T), 19k miles on a 1999.  when I open it up,  it accelerates to about 3-4k rpm, then holds back for a while. It is gradually getting worse. Any advise?

[piston_slap]

The first thing i would do is clean the MAF sensor....
It takes 5 - 10 mins to take of and then clean with
same stuff used for tape heads etc .....Maplin sell
it as a spray.... Once you have cleaned it allow couple of hours to dry and then re-install.

What can happen over time the MAF sensor can get
soot on it which causes incorrect readings....this can
cause the symtons that you have mentioned.

Also try Redex injector cleaner.....

Good Luck

[kniterider]

yep get that MAF sensor either cleaned or changed, id prob try what piston slap did with that temp sender, cant go wrong for a ?20 fix even if it dont work,dont think reddex will cure it as its only done 19,000 miles and bound to be spanking all over!, hey mines not far off 80,000 now, and goes a hell of alot quicker than when i got it, id get yours on the motor way and get it revved right up there with some miles and it will run better a german website is saying these 20v engines either turbo or non dont run in till around 150,000 miles! plenty to do then! let us know how yaget on matey

[rickardo]

Sorry to drag this up again but piston-slap.  Which temp sensor did you change, the coolant or the air?

just got round to doing this repair, hasent been so bad but now the cold and white stuff is on the way, its stated up again.

cheers

[kniterider]

just the temp sensor not the maf sensor, not quite sure where its will find out and let yas knows!!