Hi guys ,
I just hope that someone could help us with the idle of my '75 2.0. I have the car for almost 7 years now and idle was always a little bit too high. We have been trying to correct this but it got worse instead of better. We changed the distributor to a 123 ignition, we changed all the vacuumlines, the AAR has been cleaned out and the idle screw is completely closed.
The car starts at 1600rpm when cold and once it is warm it goes to 3000rpm and the idle stays there. The car pulls very well , a lot better better than when I just had it. (IMG:style_emoticons/default/confused24.gif) (IMG:style_emoticons/default/confused24.gif) (IMG:style_emoticons/default/confused24.gif)

I'm going to say you have:

a. a vacuum line disconnected or routed incorrectly, and/or

b. the wrong curve picked for the 123 dizzy -- when I installed mine I had to use one with vacuum retard, not advance, option off the throttle body -- otherwise I ended up with a situation like yours, and/or

c. your timing is just too far advanced

Sounds like a vacuum leak. If the vacuum lines have been replaced, then possibly the PCV valve if so equipped is stuck open, or the AAR is open. Or a manifold leak.

test the AAR after the car has completely warmed (and is hitting 3000 rpm) by squeezing the hose tight to close the hose. revs will drop if its a stuck open AAR.

you say you cleaned it. does not mean its working.

a little bit of difference between AAR on a D Jet and an L. i have an L so someone else who knows would tell you how to properly test a D Jet AAR.

does sound a little bit like the AAR is stuck open and is not closing.
trouble shoot it to tick it off.

good luck.

other thing might be decel valve needing adjustment.
idle vacuum is able to pull it open if its spring pressure has become weak.
this is something that has come up on L jets - not sure about D Jets.
adjust it via the nut on one of the hose nipples.

Broken intake gasket. Paid big dollars in the early 80s to not have this diagnosed. That when I decided to fix my own cars.

Carlos

3k? Definitely a huge vacuum leak. Timing can't be advanced enough to do that without some serious issues. Follow the air path...
Head, phenolic blocks, injector seals, plenum.... You get the idea, any potential place for air to get in BELOW the butterfly. But 3k is like a major hose disconnected.

Yeah, 3k is way too high for AAR as well. Get yourself a can of carb cleaner and start spraying. When the idle drops, you found your leak. Take some pics of your engine bay and we can take a look at that routing. That year should have passive pcv if I remember correctly.

(IMG:style_emoticons/default/agree.gif) but the idle screw hard and fast also (IMG:style_emoticons/default/sad.gif) another red flag with a false air idle like that it has to be one of the larger hoses ..thinking AAR also.

Thank you guys for all the suggestions. I'm gonna call my mechanic today and we're gonna check it all out. Closing the AAR tube was already something I wanted to do.
If we can't solve it , I'm gonna send some pics of the vacuum lines.
To be continued...

Robin

My mechanic picked up the car this morning and this afternoon I picked up a backup switch at the Porsche Centre in Antwerp. I had an aftermarket switch before but it was crap. Tomorrow I'm gonna have a look in the shop to see if we have any progress.

Does your shop know much about d-jet injection specific to the 914 and its changes across years? It's the kind of thing that one of us that have done it could probably fix/diagnose in minutes but would cost 1000s for a shop to learn/throw parts at etc.

Go find my thread on making a home-built smoke machine and smoke testing your entire intake tract. You WILL find the source of your intake leaks that are giving you a high idle. You will need to put some cellophane (kitchen plastic wrap is what I used) between the throttle body and the boot for the air intake box or all your smoke will just go out that way. With that huge hole covered, there is nowhere for the smoke to go but out the leaks you have. With the boot covered, ANY smoke in your engine bay indicates a leak. You may need to dig to find where it is, but you have one - and it may not be something obvious like a vacuum hose.

For me it wasn't at all obvious before the test, and clear as day after. I had a worn out throttle body. I would never had found that without smoke testing. I've also seen rust holes and cracks in the plenum. Bad gaskets. All sorts of issues.

I built the smoke tester for under $40.

Here I made it easy. This is the link to the thread:
http://www.914world.com/bbs2/index.php?act...=2&t=353039

Zach

if the thottle is completely closed then you have a vacuum leak, a line is off the runners are not sealed to the heads or plenum and or the decel valve aux air valves are sticking

(IMG:style_emoticons/default/popcorn[1].gif)

George chimed in with nothing that wasn't already said. George, pay attention.
Slotty, read the posts and share what you do along the way so we can keep helping you. Job #1, find and fix the vacuum leaks.

Update,
This afternoon I got a call from my mechanic. We have some progress, thanks to all your comments.The AAR is not working properly.When he shuts off the AAR line , the idle drops to 1200rpm when cold and 1600rpm when warm. That's already better but still way too high.He thinks there's a leak in the throttle valve or maybe the axle is worn. I don't know if these are the appropriate terms since I'm not English speaking, but I hope you understand what I mean.
He already tried to repair the AAR but it still doesn't work . He proposes to eliminate the AAR and fit an electric valve that I can shut down when the engine is warm. Is this a good idea? Hope to hear the comments from the experts.
To be continued.
Robin

AARs are available. One sold here just a few days ago. Big thread on testing and maintaining the a few weeks ago. If can find, also indicates comparable Nissan part #.

(IMG:style_emoticons/default/agree.gif) best to replace the AAR. It progressively closes as an internal heating element warms up, versus an electric valve would be open or closed. You can also take an AAR apart and may be able to free up the mechanism. There's a you tube video on that.

Sounds like he suspects the bushings holding the butterfly/shaft in your throttle body are worn.

Easy enough to check

And most of the throttle bodies are worn out on these djet cars by now

you are thinking of our L jet AAV @StarBear . different beast.

@slotty008 has a D Jet. i've read those AAVs are next to impossible to find/buy.
i think its a kind of rotary style design. don't know much about them.

sounds like your mechanic is on the ball @slotty008 .
throttles wear out on L jets. don't think the D jet version is any different.
they get wear where the throttle plate rests against the interior bore of the throttle body and the axle shaft and bushings wear.