8V High Idle

[Telf 224 2 Cars]

Hi all,

 

Post my recent 8V problems the car is finally running again.

 

I cant seem to sort the idle out however. On start it doesn't idle very high-around 1000rpm and seems to struggle to maintain the revs. It doesn't hunt as such just sounds very laboured.

 

If I sit for a minute with my foot covering the accelerator it settles and sounds ok.

 

I commute 20 miles each day and I've noticed that 10minutes or so into the drive the idle rises and remains at 1500rpm.

 

When I get to work I've turned he idle screw and brought it back to 1000rpm.

 

The next day after doing this the car really struggles to start, so I have to unscrew it a little. It runs fine but the idle always ends up creeping back to 1500.

 

During my recent problems I had every breather hose disconnected and checked them all for holes etc, I had the inlet manifold off and have checked that for leaks.

 

The car runs fine overall but this idle thing is annoying as it was always really spot on prior to my over fuel/cambelt problem

 

Any help would be great

 

Thanks

[j_turnell 137 3 Cars]

Have a read of these two articles on the main site.

 

http://www.205gtidrivers.com/articles.html/_/articles-guides/engine-related/205-gti-injection-basics-r34

http://www.205gtidrivers.com/articles.html/_/articles-guides/engine-related/supplementary-air-device-sad-r33

 

I would check the TPS is functioning properly and there are no air leaks.

Edited January 20, 2016 by j_turnell

[ATK 142 1 Cars]

Start from scratch and give it a good setup:

 

Strip all the pipework out from the manifold back, take off all pipes etc. Take off the cold start valve, AFM, throttle body, air filter housing etc. Clean them all out with carb cleaner etc and refit making sure everything is tight and no holes or leaks etc.

 

Then try setting it up as follows (this is assuming your other components spark plugs fuel pump etc are all good):

 

1. warm engine up (until rad fan kicks in) and stop

 

2. turn AFM air bypass screw fully out (weaken mixture)

 

3. turn throttle air screw fully in (Larger screw on the throttle body)

 

4. Unscrew throttle stop screw so the throttle plate only just about 'clinks' against it when returning to rest position. start engine and set throttle stop screw (smaller screw on throttle body) to 600rpm (650rpm on 1.6)

 

5. turn throttle air screw out until RPM achieves required idle speed (900rpm +/-50rpm)

 

6. richen the mixture on the AFM by turning the screw in until the desired CO reading is achieved (1% - 2%) which will raise the RPM. 1.5% ish is best.

 

7. turn the throttle air screw in until RPM is lowered back down to required idle speed in step 5

 

8. stop engine and adjust Throttle position sensor (on side of throttle body - rotates) to idle switch stop position (pin 2 and 18 continuity on a multimeter). Best way to get this done roughly is that to turn the TPS on the side of the throttle body so it just clicks as the throttle returns to rest.

 

Then set your ignition timing. for ignition timing don't bother with a light, wind the dizzy until it pinks in a low gear up a hill, then back it off slightly. You might need to wind the air screw in or out after doing the ignition timing.

 

If idle is still high either your ignition timing is too far advanced, you have an air leak or your cold start valve (SAD) is not closing up. You should be aiming for around 1400rpm idle when cold and 950rpm when warm. I set mine to 1000rpm when warm as it drops to 950 due to electrical load when lights fan etc is on.

 

Good luck!

[erbs 42 1 Cars]

That's good advice on the setup,will deffo be doing this when I get my car back

[Telf 224 2 Cars]

Thanks guys,

 

I will try the setup later- im confident about the leak and cleanliness- did all that on the rebuild.

[Alan77 78 1 Cars]

Coolant temperature sensor?

[Telf 224 2 Cars]

coolant sensor alters the fuelling signal from the ECU doesn't it? Its not over fuelling nor under fuelling.

 

I've changed it recently anyways and continuity checked and insulation checked all associated wiring. Will try the initially setup described, its probably a hangover from the troubles I had late last year.

 

Thanks guys will report back.

[Telf 224 2 Cars]

Well Ive finally got to the bottom of this - simple as usual.

 

It was the breather from the top of the filler to the airpipe just before the throttle body. Perished but not obvious until I flexed it.

 

Also found the brake vacuum hose frayed at the inlet manifold so I chopped the end off that and refitted.

 

Its now running bang on 950 rpm with no fluctuations.