Intermittent bursts of power

[reesky]

Hi everyone,

I have a 2002 1.9TDI 90bhp Octavia Ambiente.

I've noticed recently that every now and then the idle speed will raise for periods of time, (around 1200rpm instead of 900rpm) for usually around 5 minutes, and along with this goes a noticable increase of power if I drive the car during this increase in running speed.

During these periods there's also a very slight, but noticable, delay in the time it takes for the engine to slow down once i've taken my foot of the juice - only around 1/3 a second but enough to make driving in traffic a bit trickier.

When these raised revs happen I've noticed that the torque of the engine seems to shift somewhat to be quite lower down, with very little power when the engine revs over 3,000 revs.

Any ideas?

The engine settles back down again and is then its usual self, which seems very sluggish in comparison.

Could this be a turbo problem? MAF?

I've noticed a few posts on here with people reporting similiar problems but can't find anything which matches exactly.

I could disconnect the MAF to test but if I do this won't I get a Christmas Tree of warning lights on my dashboard which I'll need to reset via VAG-COM?

Please help!

[Taxi 219]

Hi.
Check the MAF yes but doing what you said and it will log a fault code but i don,t think they show a warning symbol though.
Could also be throttle position sensor/switch whatever they call it.
Have you tried an injector cleaner that you put in the fuel tank?
Also go for a short "blast" upto max revs and see if that might clear it.Maybe the turbo is sooted up.
Good luck

[reesky]

Cheers Taxi 219, good thinking.

It's alright to use an injector cleaner in this type of engine then? Anyone have any recommendations for which sort I should use? Or should I poke around the site a bit more? ;-)

I've tried the short blast thing but no better I'm afraid, revs are still up and down like a yo-yo and other times the car has the power of a 1970's ice cream van.

[Neo_VR]

Hmmm usually a fault with the accelerator pedal sender would make the engine run at higher RPM (to allow the car to still be driven with no accelerator)
maybe this is the problem but your accellerator pedal still works (this is a stab in the dark ovbiously)
you need the codes reading off vagcom really

[Taxi 219]

Agreed does need VAGCOM readings.
Use Millers powersport 4 injector cleaner its the best around.

[reesky]

Well I disconnected the MAF and it performs even worse overall although seems to have slightly more power up to 2,000 revs at which point it dropped off completely and really struggled. Didn't get any ECU lights on the dashboard when I did this.

Stuck some MIllers powersport 4 in so will have to see how that goes.

A friend has VAGCOM so i'm going to badger him to read my values.

I'll keep you posted! :-)

[Taxi 219]

Good luck and hope you find the problem