1975 914 high idle

[gwl123]

My '75 914 1.8 idles at 1600 rpm for the first 15 minutes or so. Does the car have to warm up before driving? Is the fuel mixture too rich? I shift into neutral and brake when I see a red light ahead and the 911 that I had didn't have this problem. Also the shifter needs to be carefully and slowly shifted into position something that the drivers behind don't like. Shifting into 1st makes me cringe wish it was a gated shifter...My experience so far is mixed.

[Nostril Cheese]

You likely need to replace the bushings in the shift linkage.

A high idle usually means theres a vacuum leak somewhere is the system. If you havent already, replace all the vacuum lines. There are diagrams on this site for the hose layout. Don't forget the rubber boots from the plenum to the cylinder heads.

[TheCabinetmaker]

shift linkage may need adjusting and/or you may need to replace worn plastic bushings that the shift rod passes thru, one at the shifter lever , one at fire wall and one near tranny. new bushings can make a huge improvement if the old ones is worn, easy to inspect them, they should be nice and tight fitting when new

I am not sure on the 1.8 motors, but on the 2.0 and 1.7 motors there is an auxiliary air valve to give more air to the intake when the motor is cold. it could be stuck on your car in the on position for too long maybe, again not sure if the 1.8 cars have this valve or not. look up to see if you have an auxiliary air valve.

[Tobra]

1.8 is an L jet injection system, 1.7 and 2.0 are D jet, they are fundamentally different.

[The cap'n]

They may be "fundamentally different", but L-jet still uses an AAR.

The Cap'n

[porschetub]

That idle sounds very high to be a faulty AAR even if it was sticking on,I have tested them and they don't stay on that long (can't remember),think theres another vacuum leak thats throwing the system out......someone can pop in and add to this as its hard when you are not there.
IMO any idle increase above say 1200rpm is normally caused by something else,head temp sensor etc etc,just saying

[The cap'n]

The defining characteristic of a vacuum leak on an L-jet equipped 914 is a no-start condition. Even a small air leak will prevent the engine from running. It does NOT produce a high idle.

The Cap'n

[Tobra]

I had a bug with the L jet that was leaking air around the injector seals/grommets. Ran crappy, but ran. Would run with an irregular idle and be hard to start with a vacuum leak. Anectdotal I know, but that is what it did.

[The cap'n]

It may be anecdotal, but it's spot on.

The Cap'n

[gwl123]

Well I got the idle down to 1200 thats where its at currently, but some days it goes down to 1000. This makes it easier for me to shift into 1st without hearing that crunch @1200.

[The cap'n]

Still 300 RPM too high. Have you set the timing by the method unique to the 1.8? Stock distributor, vacuum can working correctly? Timing is done per the label, engine at full operating temperature, AIR closed, 7.5 degrees BTDC, 900 RPM with both hoses off and plugged. Once the hoses are off, you should have to close the air bleed screw to get the idle to 900 RPM. Set the timing, open that screw back up a little and attach the hoses. You then adjust the idle as necessary with the air bleed screw.

Report back!

The Cap'n

[74-914]

Maybe related or not, or could be not related at all. My 1974 1.8 developed a high idle after driving it a good bit. It idled around 900 RPMs when I first purchased it from the original owner. However it was parked most of the time and hardly driven. I changed the plugs, wires, and put on an electronic ignition. Everything was timed and still idled at 900 like it always did. However after putting about 1000 miles on it, it started idling at about 1900 RPMs. No vacuum leak to be found and nothing else seems wrong. I adjusted the idle based on the Haines manual and have not had any additional issues at all. I just figured old gas, dirty lines and injectors, running it with fresh 93 octane and ethanol treatment opened it all up.

~Kevin

[gwl123]

I'll try and pour some Seafoam or Techron into the tank and use 91 gas.

[The cap'n]

I fail to see the wisdom of using 93, or even 91 octane fuel in what is probably stock engine. Before I go into a discussion of this, I'd like to see some comments from people who use and/or recommend using it under these conditions.

The Cap'n

[gwl123]

Well I got it to idle @1000 rpm. Disconnected a small hose and adjusted the idle screw clockwise. Plug hose back in and done. Did a 6 mile test run and it stayed @1000 will do another longer trip .

[porschetub]

Well done ,you are nearly there,but idle should be lower.