‘74 1.8L L-Jetronic Cold Start Low Idle, Mystery solved! Options

[Van B]

Maybe a little high, but also, running 20W-50 requires a little more effort to get it warmed up and flowing well.

[emerygt350]

Maybe a little high, but also, running 20W-50 requires a little more effort to get it warmed up and flowing well.

Yeah, I use 5w40 synth. I want my oil to reach the bearings as fast as possible on cold start up. I have plenty of oil pressure so it works fine on my engine.

[wonkipop]

Just thought I would post my warm up.
Starting (40F) (no touching the gas pedal)
https://youtu.be/5Nm7N8xJ4P8

2 minutes later
https://youtu.be/IzlGgfP5KEA

After 15 minutes driving around.
https://youtu.be/6q2CMoWxn1c

It took a good 15 minutes for it to finally go off the AAR.

My idle afr looks a little lean but it smells good so I think I might leave it there.

yeah, i'd like to get the L-jet to do that idle straight up off cold.

my renault, only 20 years old still does 1200 straight off, takes up to 5 mins to settle to warm idle depending on ambient temp. big citroen v6 much the same.
if i can get the L jet to do similar number i'd be happy.
not fighting real cold here. it never really gets below 45F.
today it was 90.

[wonkipop]

to clarify the distributor thing.

if the retard side of the vac can was no good, i don't believe it would have any effect on idle. where you would notice it is opening the throttle. the car would not pick up revs as brightly. might stumble slightly. it would be harder starting. thats with the timing done to spec at 7.5 btdc at idle.

the way that side of can works is in unison with the distributor at idle with the weights at rest. as soon as the vacuum comes off, the spring in that part of the can set up shifts advance forward (probably something like 3-4 deg). its a little tricky thinking through how that works exactly as the description in the manual seems at slightly at odds with way you go about setting the timing initially with the hoses off).

the AAV def gets you the higher warm up revs with extra O2 for the richer start up mixture - and without upsetting the vacuum can and its draw from the port near the throttle plate.

the other side of the can is going to do nothing in relation to the problem discussed here.

what am i saying?
if the cans are shot. (but i don't think Vans are).
one way around it is to work out what the ideal timing is without provision for emissions?
because i think that 7.5 btdc is the emissions setting. this is the bit i am still trying to figure out. does it stay at 7.5 and get snapped forward by the can coming off, or does the can hold it retarded further back than 7.5 and let it come back to that when it comes off.

what you are getting at @Van B ?, if replacing the distributor with a purely mechanical one. finding out that ideal idle timing setting?

@emerygt350 - you just manually turn that tap in the hose while you are warming the car up. get out and close it up a bit more as you are driving around for the first 10 minutes? or do you warm up the car standing still and just gradually close it? i'm going to get one of those taps for my experiments.

[wonkipop]

i pulled my old haynes manual down off the shelf.
i remembered its real light on L jet stuff but has the material covering the twin carb 1.8 for europe with no emissions gear.
the timing is 7.5 btdc for the carb engine. it does not even use a retard can distributor.

i sorted out the description that was confusing me a little bit in factory manual this morning. i was right with my much earlier views. you set it up ideal at 7.5 and the can does the rest by retarding it further by slipping the plate forward and losing whatever it is - 3 to 4 degrees of advance. and it comes off instantly once vacuum is lost when throttle opens. to my way of thinking if the vac can is shot that means nothing detrimental is happening anyway in terms of a strong idle. maybe if the pull rod was locked up it might cause problems, but they would be a lot bigger than a weak idle, it would be retarding you by 3-4 deg permanently as the weights tried to do their job. bog everything down all the way. and it would have to be locked up in the full vacuum position. the springs inside the can naturally rest it in the neutral position if diaphrams fail.

they also list 4 different types of distributor for 1.8s in the factory manual, but only two in the parts manual. as far @StarBear and I can work out its only the two. (but they do list two different rotors!).


---

the californian version of the 74 dist. was perverse. they left the advance hose dangling in space to ensure the distributor always worked in retard action in engine vacuum conditions. even at cruise. I'm trying to work out from the parts manual another piece of business which is the use of a speed limited rotor with some distributors and not others.
there could have been two scenarios. trying to get to the bottom of that. either 74 for one rotor and 75 for the other. or california 74/75 for one and 49 states for the other.
they don't make it easy to work out in the manual because it seems to contradict the parts catalogue. but i guess its to do with having vac advance or not?

[emerygt350]

The valve I put on the AAR is only there to tame the AAR itself. So I just close it a tad (to taste) and don't touch it again. It really has no effect except limiting the max rpms during warm up. It is great for troubleshooting though.

Retard doesn't have a performance effect, although I have noticed all kinds of goodness when I switched my 123ignition distributor to advance rather than retard. It is one or the other on those.

Careful using terms like "adding more O2 leading to a richer mixture". Normal people will look at you strangely.

If van b's car runs perfectly warm, and idles perfectly warm, I would add the valve and take the AAR out of the equation while manually adjusting the air with the valve, if everything is perfect than maybe a new one is all that you need. That would also tell you if the new one was doing what you need it too. If you put some Nissan AAR on there and it doesn't work, it may just not be doing what you want, not that there is some other issue and it wasn't the AARs fault. Those valves are 3 dollars at garden supply stores.

[wonkipop]

Careful using terms like "adding more O2 leading to a richer mixture". Normal people will look at you strangely.

i know.

but i did say for the richer start up mixture.
it is enriched by the ECU.
its the thing sending more fuel.
with an AAV you are adding the O2 that amount of ECU commanded fuel wants.

so i think i have that right.
its not causing the richer mixture.

not like a choke. which causes the richer mixture in a carb sucking more fuel out of the jet by increasing the velocity of air flow past the jet.

-----

yes i am thinking what i could do is just use your hose and tap for some troubleshooting experimentation by doing a manual version of the AAV with the AAV right out of the equation. run an alternative from the plenum with your hardware store tap on it from plenum to intake boot. just to work out if i can make a difference. run it over an approx 8 minute period. i can do that before i get hold of another AAV - which will have to come from the states and go through all the usual freight chaos we seem to still be having.

[wonkipop]

i can do one other trick manually too.
all the cooling flap gear still works on mine.
i just have the cable disconnected.
i can hold all that shut manually easily from on top of the engine for a test warm up and see if it makes any difference to the wobbly stage it goes through from minute 2 to 4.
won't make it idle higher from the initial start, but be interested to see if anything happens a little further on in things.


last time i looked the thermo still looked fully compressed but i haven't operated it in years. could pull it off and test it in the sauce pan. i think i want a new one at this point if i hook it all up again more permanently.

[emerygt350]

I was reading the old Volkswagen bible the other day and the author made a good argument for keeping the bellows and flaps working even in warm places. Less time with oil not at running temperature the better.

I just think the flap design is so cool I just need to have it working.

[wonkipop]

I was reading the old Volkswagen bible the other day and the author made a good argument for keeping the bellows and flaps working even in warm places. Less time with oil not at running temperature the better.

I just think the flap design is so cool I just need to have it working.

yeah, i'm coming back around to it.
it is cool.

[StarBear]

I was reading the old Volkswagen bible the other day and the author made a good argument for keeping the bellows and flaps working even in warm places. Less time with oil not at running temperature the better.

I just think the flap design is so cool I just need to have it working.

yeah, i'm coming back around to it.
it is cool.

Yep; I’ve always kept the flaps and bellows operational. Who am I to dispute 1960s German engineers? (IMG:style_emoticons/default/biggrin.gif)

[Van B]

Checked vacuum hold on the distributor today, it holds 25” on both sides no problem. I also pulled the cap and everything is as it should be. Points are Bosch type and Judging by the zinc coating, pretty new.

[emerygt350]

Did the plate move freely and return home nicely when you took the vacuum on and off? Twisting the rotor by hand and seeing if it returns home is also a good test to see if the weights are gummed up. George H. has a nice video where he goes over that as well.

[Van B]

I know it all works. idle climbs and descends as it's supposed to when I remove or connect the lines.
honestly, I just do these things so the few of you who are helping me figure out why the cold idle feature isn't working will be satisfied.

a distributor problem is a red herring IMO. The attributes of a distributor problem would affect all ranges of operation not just idle at cold start. I've verified retard at idle, and full advance at 3k RPM.

the most interesting clue to date was when I bypassed the AAV and connected straight from the intake boot to the manifold. That resulted in a massively high idle during cold start... nearly 3.5K!

[emerygt350]

Just trying to make sure all the easy stuff is covered... The reason why it matters is you can't time it correctly if the plate is not moving freely. Timing affects idle.

[wonkipop]

I know it all works. idle climbs and descends as it's supposed to when I remove or connect the lines.
honestly, I just do these things so the few of you who are helping me figure out why the cold idle feature isn't working will be satisfied.

a distributor problem is a red herring IMO. The attributes of a distributor problem would affect all ranges of operation not just idle at cold start. I've verified retard at idle, and full advance at 3k RPM.

the most interesting clue to date was when I bypassed the AAV and connected straight from the intake boot to the manifold. That resulted in a massively high idle during cold start... nearly 3.5K!

there is a checklist procedure for the distributor vac cans in the shop manual you downloaded van. at different rev ranges. if you really wanted to be sure the cans were working properly. Group 1 engine, section 2.3 - 2/4 for a couple of pages after that. =
....if you got an hour to waste. (IMG:style_emoticons/default/smile.gif) sounds like it works though.

anyways merry xmas gentleman. been fun going over this stuff. got myself a checklist thanks to all this and i can go down the rabbit hole and disappear for a day or two in the shop.

thanks to emery i'll muck around with a tap for fun. (IMG:style_emoticons/default/beerchug.gif)

i've been getting my 94 falcon ute (aussie ranchero?) ready to paint lately so i've been neglecting the 914. time to get back into it. see if my rebuilt orig fuel pump can really last more than 5 minutes after i put it back in the car. (IMG:style_emoticons/default/beer3.gif)

[emerygt350]

I am to the point now where I am running out of stuff to fix. My damn mustang needs the transmission rebuilt but that is beyond anything I would attempt. Oh well. My sister in law from Bavaria will be here tomorrow so I can have fun with her and the Porsche. When her father found out I had a Porsche he said "I have never heard of a 914" (IMG:style_emoticons/default/sad.gif)

[Van B]

been on a little bit of a tangent the last couple days in my google searching. I started thinking about the fact that the thermo time switch aka temp sensor is NLA... and I realized it might be good to find a comparable replacement that is readily available. I've been pulling on the 912E part number thread to see where the supersession goes and it looks like there may be some options out there.
Unfortunately, info is hard to come by and silly things like thread pitch can be a problem. I think I'll head down this rabbit hole for a while and see what comes of it. If I can come up with a readily available $20 replacement part that works, then I think it will be worth it.

Merry Christmas!

Van

[StarBear]

been on a little bit of a tangent the last couple days in my google searching. I started thinking about the fact that the thermo time switch aka temp sensor is NLA... and I realized it might be good to find a comparable replacement that is readily available. I've been pulling on the 912E part number thread to see where the supersession goes and it looks like there may be some options out there.
Unfortunately, info is hard to come by and silly things like thread pitch can be a problem. I think I'll head down this rabbit hole for a while and see what comes of it. If I can come up with a readily available $20 replacement part that works, then I think it will be worth it.

Merry Christmas!

Van

(IMG:style_emoticons/default/popcorn[1].gif) would like to see this happen! Onward!

[StarBear]

Saw this in the current Pano magazine (Tech Q&A) - the 1999 version of the AAV for a 911! Same principle and purpose, but a "more reliable" approach.