Fast Idle

[Paint Legend]

I did check prior posts on this topic with no real luck, so sorry if it's been covered a 100 times already. I just gave my 74 1.8L 914 L-F.I. a tune up and it runs great accept for a fast idle. I have the idle screw all the way in and it still runs at about 1800 - 2200 rpm. My Haynes manual is worthless for trouble shooting. I have seen the specs for the sensors, but would like to approach it in a systematicly manner vs. just testing each sensor. Any thoughts or advice??

Thanks
Tom

[pbanders]

Two immediate thoughts - overadvanced timing and/or air leaks in the intake.

Brad Anders

[Va914]

Take a look at the Aux air valve. If its stuck open you will have a high idle and lean mixture. A quick test is too carefully bend the hose to the aux air valve to restrict the air to the air valve. If the Idle drops the aux air valve is sticking or bad connection.

Best of luck.

[scotty914]

clamp the hose to the decel valve, mine was bad and so was some one elses on here.

the decel valve it the one next to the battery on the side of the motor



------------------
scott thacher
75 1.8 running at last
75 under rust
(fine german rust)

[JP Noonan]

Take the oil filler cap off and then cover the hole with your hand to seal it. The gaskets go bad all the time. Also look at each and every vaccuum hose and T fitting a for a tight connection. Timing too advanced. Or a bent vane in the air meter.

[pbanders]

I know you have AFC, but here are all of the possible reasons listed in the VW MPC troubleshooting guide for a high idle - many if not all apply to AFC, too:

1. Throttle valve not closing (misadjusted cable, binding, bent shaft, etc.)
2. Adjusting screw out-of-adjustment
3. Air leak - hoses between intake pipes and air distributor, vacuum hoses, intake pipe gaskets on cyl. head, rubber mountings for injectors, crankcase ventilation
4. Defective aux air regulator
5. Defective decel valve
6. Overadvanced timing

Brad Anders

[Clay Perrine]

From 1.8 AFC experience. Check the Aux air regulator. It is on the left side of the intake next to the oil filler. Make sure it's not stuck open. Check the Decel valve on the right side of the engine compartment. It has 2 large and 1 small vacuum line running to it. Make sure that the 2 large lines don't pass vacuum when the engine is idling. Check the throttle cable adjustment. If it is too tight, it can hold the throttle open. Check the timing.

Unlike MPC on the 1.7/2.0 a vacuum leak will lean out the system and cause the engine to die.

Clay Perrine
74 1.8L Signal Orange "Frody" (My Wife's Daily Driver)
73 2.4L MFI Six "Igor" (Under Construction)

"Friends help you move. Real friends help you move all your 914 parts"