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Fixing the Carrera's Surging Idle / L-Jetronic
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- čas přidán 27. 04. 2022
- This is a film about how to fix the surging idle of cars that use Bosch's L-Jetronic / Motronic injection system, including the air control valve, specifically for my 87 Porsche 911 Carrera.
#porsche911 #classicporsche #restoration
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![[Программа самообучения] SSP 4. Bosch L-Jetronic Injection](/img/n.gif)
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.
I really enjoy your style of videos. One thing that struck me, should the left side of the 911 be little bit higher to compensate for weight of the driver? Now it's the opposite way it seems or maybe it's just the floor angle.
I was justtttt about to mention this :)
I bought Löwe idle control valve last week for Porsche 944 S2 and it is faulty. After installing it, the idle was following one of the following scenarios:
1. 900rpm as expected but then 700rpm when AC turned on
2. After pressing and releasing gas pedal the idle would randomly
2.1 Drop to ~400rpm and stay there until driver pressed gas pedal to raise rpm, car was shaking .
2.2 Drop to ~1800rpm and stay there until driver pressed and released gas pedal do raise rpm
2.3 Enter infinite loop while the idle was rapidly changing from 900 to 1800rpm and back until gas pedal was touched (like I would be revving an engine on a red light to start a race)
2.4 Rarely go back to 900 or 700rpm
My mechanic cleaned and resintalled my OEM ICV and it works well enough now.
@@8359s Thanks for the insights, Robert. I’m sure they’re interesting for many out there.
Really enjoyed seeing the mysteries of this old electronic system unveiled. Thank you for another excellent video.
😊
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
Thanks, mate!
Sounds absolutely spot on now, so rewarding when you get these to idle like this. 👍
Thanks, David. Yeah, it’s giving me waves of joy these days to start it.
Brilliant, comprehensive, essential. Thank you for sharing your knowledge. You helped me solve all my problems.
Mahalo!
Thanks, Brendan!
All of them, really? 😆
the videos are so great in quality and music selection.. and the voice overs... it is just enjoyable
Thanks, mate. Very much appreciated.
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!!
You’re welcome Scott!
Don’t forget, some of them have the purpose of testing and would cause the mixture to go lean which might not be good for the engine’s temperature.
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!
In fact today’s systems work pretty much the same way. The cool thing about the early eighties systems is that it all was so new and leading edge back then.
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.
Thanks, Bob. One day I’m going to collect that debt! 😆
Thanks for put in practice common sense! The world need more of that.
Outstanding content as usual.
Thanks, John. 😊
I have been looking forward to a new video from you. Danke Johannnes!
Thanks, mate.
It took a while …
It nice to see your repair fixed the surging warm...
It looks as if it did. 🤞🏼
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.
Thanks, mate. 😆
I’m too very happy with the music this time.
Great video, good to have you back.👍👍
Thanks, mate. I had to move my workshop one more time. Real estate in Bavaria … 🙄
@@GreasyFingers Auweia. Hier in Franken hab mich meine Schrauberhöhle seit 11 Jahren und noch keine Mieterhöhung 🙊
Da kannst Du echt von Glück sagen, der Umzug einer Werkstatt ist ein Riesen 💩
Mein Vermieter hatte mir ein Covid-Testzentrum auf den Kopf gesetzt - mit einem Zwischendeckchen aus OSB-Platten. Ich habe irgendwann meine eigene Flex nicht mehr gehört bei einem Parteiverkehr von 50 Leuten pro Stunde.
Excellent presentation. Very interesting. Thank you.
Cheers & thanks!
Your content is fantastic. Thank you so very much
You’re welcome, mate!
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.
Thanks, Achim.
That’s what we’re living for, isn’t it?
I saw your Saab at the 8:43 mark! I thought you were a genius before, but now i know for sure.
Thanks a ton, Chris.
Unfortunately the Saab doesn’t belong to me, but I love it a lot.
My friend Andreas has optimised it in such a level of detail, it’s an immense pleasure to drive it.
Excellent video. Thank you.
Thanks, mate!
Great video!!Nice information to a simple problem!🙂👏👏👍
Thanks! It sounds simple, but it’s a real plague.
Gorgeous vehicle
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
Die Marelli sieht bestimmt klasse aus und macht einen perfekten Café. 😆
Great video, thanks for sharing!
Thanks & welcome. Please share it with friends.
I most definitely will as all your videos I have watched so far have been very helpful and real life encounters. Thanks again! @@GreasyFingers 😉
Useful and informative video as usual.
Yeah, now all you need is surging idle! 😆
@@GreasyFingers Yeah but I have always considered that term -surging idle - a contradiction - just like clearly confused. That would be me. 🙂
😆😆
Another great video :)
Thank, mate!
Really great information
Thanks, Khalid.
Excellent…much respect.
Thanks, Steven!
By the way, the music accompanying the video is really nice.
Thanks, Lester. In fact I’m very happy with it too.
Another interesting video to watch on my lunch break,I've sold alot of those valves 🤗
Cool, thanks.
Have you been a parts dealer?
@@GreasyFingers I started in 1987 for 6 weeks helping in parts in 6 months was in control over the guy there we moved to a purpose built centre on a business estate in 1990 and I left in 2017 30years of my life .... management made me change direction,was all about profit not the person or all my experience, it was a Porsche centre in Newcastle upon Tyne UK
It’s a shame when money is all that counts.
Looking forward to your comments on my stuff …
@@GreasyFingers haha
Regards Colin
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
Yeah, servicing was not their main concern back in the days.
I’m really happy I found this aftermarket thingy, otherwise the issue might have grounded Walter for the summer. 😱
@@GreasyFingers I had to make do with a non OEM fuel pump as the Bosch could not be disassembled without specialized equipment. Alfa, 911 and BMW 2002tii with mechanical fuel injections used the same fuel pump and consequently NOS pumps are running over $1000
Gute Arbeit!
Danke, mein Freund.
Nice getting to know some more "down to earth" solution finders! This is how god's mechanic works! 😄👍
Thanks, mate!
Thanks for the tip on the ECU settings. I will try to "play" with mine.
Welcome.
Avoid 3 and 7, for they make the mixture more lean.
@@GreasyFingers Thank you!
@Jay Mac Exactly, Jay! The lean settings I’m trying to avoid. I have it running on 6.
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? ;-)
Thanks, mate.
No secret, the pre-owner replaced them at some point, I guess.
The lip does great. If it ever touched the curbs I wouldn’t notice.
Good job!
I think i have the same part in my E30 325i.
My 318is(M42) have different part
I’m not quite sure, because through the eighties there were updates of the system in a short sequence. BMW was known for quickly lifting their engines to the latest technology.
this was sehr gute! I wish you owned an SC like me and then I would be even more informed.
Thanks, Johnny.
You know what? It happens I have a K-Jetronic car too and in fact I contemplated about making a similar film about it like the one you just watched.
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.🤷🏻🇬🇧
Cheers for your Cayman. I had the 718 for a day last year and I also know the 991 pretty well. Conclusion: the Cayman/718 is the real successor of the 911.
I enjoy troubleshooting the L and K Jet fuel systems. Most issues are usually air leaks or bad grounds.
Hi Jay, yeah, that’s exactly true.
Very satisfying to repair.
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.
Thanks for commenting, mate.
I tried that too, but it didn’t solve the problem. Actually, the flap moved freely in the first place, so my problem must have been of some kind of electrical nature.
The sound of a flat six with no sport exhaust is beautiful .
That is definitely true. I much prefer it over the noisy aftermarket products.
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 commenting!
Yes, it’s a great system. And how innovative it was! When I started studying automotive engineering, we were so intrigued by the electronics that we thought it does everything, really EVERYTHING. Does it even need an ignition distributor? 😆
@@GreasyFingers I installed a Pertronix brand Hall effect sensor as a replacement for the old points and condenser setup and I think it’s a perfect compliment to the L-Jet FI. Throttle is crisp and smooth at every RPM!
@@Van-tastic Awesome! And the flame thrower coil too? Do I have to do that as well?
@@GreasyFingers I kept the Bosch blue coil. The Pertronix Ignitor II needs a coil with close to 3 ohms so, the Bosch was still the right choice. I don’t know if they have one for your ‘87 911, but I bet one would work great in the Alfa!
@@GreasyFingers Does the ‘87 still use a distributor or does it have a more modern ignition?
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…
Thanks for the feedback, mate.
That’s really catching my interest now … what injection system is installed in your TVR? Some Lucas product?
@@GreasyFingers it’s an MBE ECU with Lucas injectors and Lucas lambda’s. I think it is characterized as alpha-N (alpha for the angle of throttle plates and N for the engine RPM) - there is no air flow sensor. The ECU uses the alpha N data to reference a look-up table (the map) and provides ignition and injector opening outputs. The ECU also monitors the lambda’s to provide short term fuel trim (+\- 30%) to account for variation in running, relative to the factory map. The short term fuel trim outputs are also used by the ECU to build up a table of long term fuel trim that acts to supplement the factory map for an eventual stable overall engine map. It’s a relatively simple system, but works quite effectively.
Set-up is a bit of pain, but not too complicated.
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.
Thanks, Isai. I wasn’t aware!!
Great video, sir. You'll notice that my little VW got a big brother...
I did! It’s a 3.2 Targa, right?
@@GreasyFingers 2.7, but I'm going to shop for a 3.0 or a 3.2 to make it more fun.
@@garagechronicles9008 Hmmm. I personally prefer the 2.7 over the 3.x engines.
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? 👍
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.
No, I didn’t.
I’m pretty much the “keep it original” guy.
I’m also not on good terms with electronics.
Air cool life 😎
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.
You hit the nail to the head!
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?
Thanks for pointing that out, man. It’s amazing how people see this.
Please note my comment that I pinned to the top of the comments.
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
Yes, I’ve commented to that right after the release of the film.
Is your lambda connector non standard? I was expecting a round plug with three internal pins.
Hi Rob, you have the eye of an eagle, you’re right! I had replaced it at some point and couldn’t get hold of an original one.
What is the name of that aftermarket idle valve?
Give me your name, mate, and a friendly word and I shall answer your question.
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.
Thanks for that comment, Paul. There’s a German guy who dealt with exactly this and described the solution of the problem including an how-to about replacing the affected transistors.
It’s a murderous effort to solve it and I’m glad yours is back on the road.
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
Thanks, mate.
I hope you could enjoy it rather than using it as instructions to get yours „unsurged“.
Followed your steps and then changed the air control unit with a spare used one. After a week and 100km of driving in various traffic, Ludwig has so far never surged at anytime. Long may it continue. Dankeschön
Makes me really happy. Very reassuring.
Anyone know the name of the aftermarket shop the air valve came from?
The manufacturer‘s name is Autosensor Berlin, www.autosensorberlin.com
what does the arrow on the unit mean?
It indicates the air flow direction.
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?"
Wow 😎
😊
I noticed that the direction of the flow arrow on the ICV was different on the later aftermarket unit...
Thanks, Michael.
Here’s the story: when I create my films, I basically have the camera running all the time. 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.
And that’s what you’ve uncovered!
When the car was back on the road already with the new valve, I had to build the old Bosch in one more time to create some more footage and doing this I accidentally flipped the valve.
Did it run with the valve in reverse?
@@911engineguy Yes it did. 🤪
@@GreasyFingers Interesting! I actually bought one of the aftermarket ones and it hunted just like your car in the video.. so the shop sent me another and it worked perfectly.... Did you try cleaning the valve portion of your original Bosch unit, with brake/parts cleaner to get all the old oil out?
@@911engineguy Yes, I did. Already last year with the camera off. Zero effect.
I guess the aftermarket valves will have some quality fluctuation, but if you can get five new ones for the price of one used original …
I much prefer the smooth jazz to the guitar and the blues.
Either is classy. ✌
Is that a new engine in the car?
No, it’s just the one that belongs there.
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.
Man, you really have the eagle‘s eye. It’s incredible you’ve spottet the arrow thing!
Here’s the story: when I create my films, I basically have the camera running all the time. 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.
And that’s what you’ve uncovered!
When the car was back on the road already with the new valve, I had to build the old Bosch in one more time to create some more footage and doing this I accidentally flipped the valve.
@@GreasyFingers oh haha the cinematography is great, I just know how detailed you have to be working on those things. I still love them none the less probably only reason I still mess with them, love hate working on them I guess. :D Keep the great videos coming! Secretly I was hoping you would come up with some trick or something I didn't know. In this case the rabbit hole is deep with the surging and still some where you get it adjusted just right for wide open throttle but doesn't idle or other crazyness haha
👍👍👍👍👍👍👍👍👍👍👍👍👍👍👍👍👍👍👍👍👍👍👍👍👍
Danke, Ernst. 😊
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 !
Thanks, Mark. 😆
Annoying music but good content.
🎸
L jet is almost easy... k jet thats something...
Piece of cake.
These things always crap out on the Mercedes. I always bought a new one.
Thanks for commenting, Corey. Did you buy an aftermarket one too?
@@GreasyFingers yes. And honestly when I measured it, it was a little off from the Bosch. But car operated fine. 560sel 1988 Mercedes. Similar system.
Great video, but could you NOT use that horrible music?!?!?!?
Generally people like my music selection, but fact is, you can’t please anyone.
@@GreasyFingers Sorry - it was the "rock" music that made me angry :-). You are right otherwise your selection is great! Thanks btw for a great inspiration on roads, went with my 911 to Forst today - a little hidden gem!
Thanks, mate.
The rock music was intended to be annoying to underline how annoying this problem was to solve. 😊