Fixing the Carrera's Surging Idle / L-Jetronic 

Dear viewers, in a few shots of this film the air control valve has been built in upside down. Here’s the story: when I create my films, I basically have the camera running all the time and slowly the script of the films is evolving as the repairs progress. When I have enough material to tell my story, I start editing and in most of the projects the „live“ material is sufficient. But sometimes I need to film a few more angles or make a second shot of the same scene because of the original shot being out of focus or something of the kind. When the car was back on the road already with the new valve installed and working properly, I had to create some more footage and therefore build the old valves in one more time. Doing this I accidentally flipped the valve and some of this footage went into the film.

Really enjoyed seeing the mysteries of this old electronic system unveiled. Thank you for another excellent video.

The features of this injection system seem to put a lot of modern systems to shame in terms of usability. Lovely video Mr. Fingers, good to see you upload again.

Thanks for put in practice common sense! The world need more of that.

Brilliant, comprehensive, essential. Thank you for sharing your knowledge. You helped me solve all my problems. Mahalo!

I really wnjoy the information and the style. I have owned the same 76 911s for 30 years. It doesn't get driven enough. Your attention to detail is great

Sounds absolutely spot on now, so rewarding when you get these to idle like this. 👍

I've been through my L-Jet system a few times. I was today years old when I learned about the mixture settings potentiometer on the ECU. Thanks for that!!

Lots to digest here, especially for someone who has never felt like God’s Mechanic. Thanks for your excellently crafted videos and for your inimitable style. Fellow Carrera owners all owe you a beer or two.

the videos are so great in quality and music selection.. and the voice overs... it is just enjoyable

I enjoy troubleshooting the L and K Jet fuel systems. Most issues are usually air leaks or bad grounds.

Excellent presentation. Very interesting. Thank you.

Outstanding content as usual.

It nice to see your repair fixed the surging warm...

From gods own mechanic to a non-starting car. 🙂 ‘The moral of the story is to buy a new part… no not really’.😆 Thanks again for bringing us a bit more knowledge and experience via your entertaining mind. Love the music.

I have been looking forward to a new video from you. Danke Johannnes!

Your content is fantastic. Thank you so very much

Gorgeous vehicle

Excellent video. Thank you.

Great video, good to have you back.👍👍

Isn’t it nice to hear the magic sound of a flat six again. Perfect, spring is here the temperature is charming and supporting warmup. Fuck the gas pump and let’s go for a ride. Live the moment! Thanks for sharing experience and passion.

Great video!!Nice information to a simple problem!🙂👏👏👍

I saw your Saab at the 8:43 mark! I thought you were a genius before, but now i know for sure.

Great video, thanks for sharing!

Really great information

Excellent…much respect.

Super. Ich hab das gleiche problem in der 90er gehabt mit ne Lampredi Motor. Diesmal kein Bosch sondern teile von M.Marelli. Die dinge nerfen einfach. Sehr gute eklährung. Immer klasse bei dir. I Affe

Your original IAC valve @ 2:54, The "fixed" @ 5:54, and the first aftermarket replacement @ 8:09 are all installed backwards. Arrow facing away from the intake boot. The working correctly @ 10:17 is in the correct orientation, arrow towards the intake elbow

Useful and informative video as usual.

Thanks for the tip on the ECU settings. I will try to "play" with mine.

Good job! I think i have the same part in my E30 325i. My 318is(M42) have different part

Everything should be repairable, once you understand how it works and you can take it apart you should be able to fix it. Why won't Porsche make new ones when they know many of these much loved classic cars are still around? 👍

Brilliant stuff. Thanks again. FI, in general is a semi mysterious thing that bedevils me. My current action resto project is a 91 E30 BMW with a M42 engine with Motronic FI so this is timely. Yeah, what is it with Bosch making parts hard to service-I'm thinking of an Alfa Fuel pump for a Spica system

Another great video :)

ah, the ins & outs and ups & downs of AFR. the beast must be fed - but only with exactly the right amount at exactly the right time. such a fussy creature.

By the way, the music accompanying the video is really nice.

Gute Arbeit!

The sound of a flat six with no sport exhaust is beautiful .

had a bmw once with the motronic system with the same fault as the Porsche. Dunked and sprayed the "regulating end" or "flap" in carb cleaner while moving it manually thru open and closed position. When its clean, it should make a clacking sound when you shake it (quickly rotating it back and forth around its axis) which indicates that the "flap" is moving freely in the housing. Also exercise the opening and closing of the flap several times under cleaning. When the ignition is on there should be, at least on my car, an audible buzz from the ICV.

Nice getting to know some more "down to earth" solution finders! This is how god's mechanic works! 😄👍

Another interesting video to watch on my lunch break,I've sold alot of those valves 🤗

Engine bay looks great, so much cleaner without AC hardware. What’s your secret for keeping cad pieces bright and shiny? Car looks great lowered how’s the front spoiler lip holding up? ;-)

this was sehr gute! I wish you owned an SC like me and then I would be even more informed.

I have a 1974 914 with the first version of L-Jetronic. It’s interesting to see what parts remained the same and what parts they changed over the decade. Your IAC may have caused you problems here, but I still think it’s a fantastically simple and genius device. Cold starts with only an Aux Air Valve can be a bit challenging on my car because the antique computer and Air Flow Meter don’t have enough sensors or processing power to accurately understand the conditions.

Thanks for the video, it will help me troubleshoot my issue. On a separate note, you probably fixed this already, but around minute 13:31 when you engage reverse, the white rear lights do not come on. May be the switch or light bulbs themselves.

Ah the magic of a closed-loop FI system. In my 2001 TVR Cerbera, I have to frequently ‘tune’ the open loop (no airflow sensor/meter) system, which uses throttle position sensors (one for each bank) and narrow band lambda sensors, to attempt some sort of closed-loop running - works better than I would expect, but never as well as my 911…

Excellent investigation Inspector Greasy😉….I have a Cayman S and can’t even SEE the engine to do anything. I love those air cooled wonders but prices are astronomical.🤷🏻🇬🇧

I much prefer the smooth jazz to the guitar and the blues.

Great video, sir. You'll notice that my little VW got a big brother...

Did you ever consider going custom ECU and massively simplify complexity and fuel economy (...at least after implementation)? In germany, as far as I know, it's relatively easy to retain TÜV especially if you'd go closed loop with a Breitbandlambdasonde.

Air cool life 😎

Uncanny timing. Went for a drive today and it was hunting non stop to the point of embarrassment. Came home, turned on the box and there you were. Dankeschön

I noticed that the direction of the flow arrow on the ICV was different on the later aftermarket unit...

Compare 6:00 to 10:30 not that you have the arrow pointing up in the working installation and down in the not working installation. Did you mount the valves in diffrent directions on purpose? Or was the original just mounted in the wrong direction?

Is your lambda connector non standard? I was expecting a round plug with three internal pins.

what does the arrow on the unit mean?

What is the name of that aftermarket idle valve?

Anyone know the name of the aftermarket shop the air valve came from?

Hello, I am taking part in a research project. I could not find almost any information about the "main relay" of Porsche 912. Can you help me with this? "What is the main relay of 912 L jetronics used for?"

Is that a new engine in the car?

Good watch, noticed something maybe nothing but will shoot the arrow on the housing was facing down if that matters. In the end it was aimed up towards the intake. I am always a fan of remove it all install new aftermarket ecu maybe throw some itb's :D honestly spent too much time banging my head on the wall with those old fuel injected things, would almost rather a carburetor setup.

Wow 😎

Many hours spent exploring this issue on my '88 Carrera Sport late last year - a very similar process of discovery (including aftermarket ICV replacement). My issue finally got resolved through an ECU recondition (the idle pins were confirmed as faulty); the resistance on my old Bosch ICV was way out of tolerance and there was a long standing internal burn mark on the wire leading to the valve so I guess your theory about a faulty valve frying the ECU may well be correct. I laughed at your 'master mechanic with god's own hammer comment' - I felt the same every time I thought I'd solved the issue. Beautiful video as always - almost as beautiful as the car itself.

👍👍👍👍👍👍👍👍👍👍👍👍👍👍👍👍👍👍👍👍👍👍👍👍👍

Annoying music but good content.

F'ck thats a cool rumble from a Porshe . Sounds like a hot Cam from an electric controlled fuel injected car .. Wish mine sounded like that ! Arrmm , Thats right I dont own one !

L jet is almost easy... k jet thats something...

These things always crap out on the Mercedes. I always bought a new one.

Great video, but could you NOT use that horrible music?!?!?!?