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

[Van B]

Oh man this is gold! Thank you good Sir!

[wonkipop]

Oh man this is gold! Thank you good Sir!

(IMG:style_emoticons/default/smile.gif)


the fuel injection section of the manual is a bit scrambled between D Jet and L Jet stuff.
you have to pick through it carefully to make sure you are reading the right bits.

[wonkipop]

Wonki, I will pay you money for that manual! Give me that manual lol!

Also, thanks by the way. I’ll chop up a socket and see if I can make that tool.

IMO all these basic sensor are eligible for the modern day remove/replace strategy. They’ve served their time and have earned a retirement. I’ll test it after I take it out and if it’s still good, it earns a place in the spares box!

yeah, somehow, as a result of misfortune more than anything else i have ended up still having a car that is very intact.

a pathetic 76 hp L jet 1.8 with star steelies and original paint (with wrinkles and scars like me). my program at this point is to preserve it on as a running artefact and only get rid of any bits i find that are clinically dead. the rest of it can use a walking stick or painkillers to keep going like the owner. the nice thing about the 1.8 though is most or nearly all of them came with the sway bars so are pretty sweet in the suspension/chassis department.

i'll definitely be paying attention to what you discover digging around in yours and any good substitute items.


don't know if you have had prior experience with type 4 engines @Van B, but there are a few dumb little traps in there for the unwary.
check the torque settings for the oil drain screen plug when you do an oil change.
that one caught a few folks out back in the day who were used to type 1 or type3 engines. you don't want to over tighten that one.

another handy little book that fits in your pocket is called technical specifications.
you probably know about it?
its easier sometimes to get torque settings for bolts etc in that than digging through the hundreds of pages in the manual.

[Van B]

Mine came with a lifetime of records, even the original invoice! The owners manual, just like a proper manual, has all the torque specs for every bolt you’ll touch during routine service.

But now that you’ve given me a real service manual, it’s game on!
This is basically a new experience for me. I can remember my dad and grandfather building a 914 engine for my dad’s car when I was young, but I was too young to do much more than hold the wrneches.

Speaking of that screen, the owners manual gives a range of 7.4 to 9.4 ft lbs. I saw Ian said he goes to 9, but I’ll shoot for the low end if the treads are still good enough to stay tight at 8… maybe even some safety wire just for peace of mind.

This car will never hold a candle to my 996 in handling or speed, but it doesn’t have to. The experience of driving this 914 is so simple and pure I’ve started to use the term “motoring” again.

I drive the 996, but I go motoring in the 914 (IMG:style_emoticons/default/driving.gif)

[wonkipop]

thats great. sounds like you picked up a real nice car.

the factory manual gives the upper value on that strainer plug. 1.3 mgk. (9.4 ftibs).
i am used to using metric settings here.
i usually set it to a bit under too.


996, very good.

i run around most of the time in renault RS 172 i have had for nearly 20 years.
a bit more frenzied and raw than a 996.
can get on your nerves a bit on a long trip.
i keep a citroen xm for long trips that i don't want to get out of the car staggering around afterwards.

the 914 is a perfect antidote to them both.
as you say - (IMG:style_emoticons/default/driving.gif) (IMG:style_emoticons/default/w00t.gif)

the 914 is the easiest to work on in many ways.
and parts are getting harder but not impossible yet.
the citroen is a real headache. its only a 99 and parts are getting real thin already.

[StratPlayer]

I just had a microsquirt sys. installed on my 2.0. Still working out some bugs but very happy with this system.

[wonkipop]

@Van B

i just realised you are in maryland?
where my 914 originally came from.
Capitol Porsche+Audi. hyattsville. 1974

owners worked in DC then moved to madison wisconsin.
which is where i found the car when i lived in chicago. 1989.

been with me ever since in melb/perth/melb aus.

[Van B]

I’m an Air Force transplant here since 2019. My actual citizenship belongs to the Republic of Texas. (IMG:style_emoticons/default/shades.gif)
Not much of a car culture around here… mostly a demolition derby.
There is a silver lining though, people who do love cars appreciate seeing cool cars much more because they are so far and few between.

It’s interesting about the old Porsche Audi dealer combo that existed back when these cars were new. There are only 2 Porsche dealers and 2 Audi dealers around DC these days, and I bet they don’t go back far enough to be the same dealership.

It would be cool to know where the old dealer was. I could do a recon for you one day and see what the place looks like now!

On our actual topic, I’ve got a URO replacement temp sensor II en route. I’ll plug it in and see what happens!

[wonkipop]

keep us posted on the sensor.

yes texas, went there often for trips when i lived in chicago.
best little country in the whole USA.
it felt like australia and cured my homesickness.

the address for the dealer stamped in the service manual is
3110 Hamilton Street, Hyattsville Maryland.

[Van B]

So, I just googled that address. Kinda sad to see that it’s nothing but a strip mall now. But when you look at it on google maps, and see the strange layout of the parking lot, you can definitely tell that it was a car dealer on a corner.

[Van B]

Ok folks, I’m trying to be cool here, but I can’t f**king believe what I just found!
My car has Bosch WR7DC plugs in it, which have a 13/16” body, which doesn’t fit in the cylinder! The body bottoms out against the head when the thread is only about 2/3rds of the way in! WTF?!?
It really makes me wonder about these so called “Independent Porsche Mechanics”! I won’t name the REPUTABLE shop in Atlanta that did my PPI, whic included a compression test, but holy shit what a hack!!!!! Man I’m pissed!!!!!

Alright, let me take a breath here and ask what plug is preferred that has a M14 thread and 5/8 body?

[StarBear]

On my 74 1.8L, I use NGK BP6ES. The BP6S are a bit shorter but work fine too. I don’t drive it hard; just local touring mostly. (IMG:style_emoticons/default/driving.gif)

[Van B]

Well, now that I have four plugs that fit, the car definitely runs better. I’m still so pissed that a guy who sells himself on being a classic Porsche specialist could miss something so damn basic.

I also replaced the temp II sensor. No change on cold start, but it was pretty warm here today so I didn’t expect the computer to go into cold start mode based on readings from the temp switch anyway.
It does make me think about finding a temp switch that has a much higher temp window. I think modern knowledge of engine wear has taught us that getting the oil pressure up as quickly as you can provides a huge benefit to engine longevity. The reasoning of the 914 era was to overcome cold engine/oil friction so the car would stay running. Thus, it makes sense they would choose a 15C/55F temp switch.

[Van B]

On my 74 1.8L, I use NGK BP6ES. The BP6S are a bit shorter but work fine too. I don’t drive it hard; just local touring mostly. (IMG:style_emoticons/default/driving.gif)

BP6ES was all that I could find locally today. I might try the projected tip BP plugs in the future. But for now, I’m just glad I caught this and I have a sealed combustion chamber (IMG:style_emoticons/default/dry.gif)

[emerygt350]

getting the oil pressure up as quickly as you can provides a huge benefit to engine longevity. The reasoning of the 914 era was to overcome cold engine/oil friction so the car would stay running. Thus, it makes sense they would choose a 15C/55F temp switch.

Oil pressure while cold should peg to 60 at idle almost immediately.

You are still having low cold idle? Did you pull the aar hose off the plenum yet while it is running low and cold?

[wonkipop]

So, I just googled that address. Kinda sad to see that it’s nothing but a strip mall now. But when you look at it on google maps, and see the strange layout of the parking lot, you can definitely tell that it was a car dealer on a corner.

i was expecting it find out it was a mcdonalds. (IMG:style_emoticons/default/smile.gif)

interesting about the spark plugs.

[wonkipop]

So, I just googled that address. Kinda sad to see that it’s nothing but a strip mall now. But when you look at it on google maps, and see the strange layout of the parking lot, you can definitely tell that it was a car dealer on a corner.

i was expecting it find out it was a mcdonalds. (IMG:style_emoticons/default/smile.gif)

interesting about the spark plugs.

[wonkipop]

getting the oil pressure up as quickly as you can provides a huge benefit to engine longevity. The reasoning of the 914 era was to overcome cold engine/oil friction so the car would stay running. Thus, it makes sense they would choose a 15C/55F temp switch.

Oil pressure while cold should peg to 60 at idle almost immediately.

You are still having low cold idle? Did you pull the aar hose off the plenum yet while it is running low and cold?

theoretically a good tip for Van B and me.
but its a bastard of a hose to get off easily that one.
its very short and curved.
to get that off i have to unbolt the AAV and manouvre it to pull the hose.
its because its so short its virtually impossible to push it back far enough off the plenum or AAV connections.

but i tend to think it probably is the AAV.
looks like Van B's CHT test and replacement knocked that sensor out of the equation.
i tested mine in situ 2 years back and it was working so i never bothered to remove and change it.

i'm going to try and take a real close look again at my AAV at christmas and see if i can find out anything concrete about just what rate it should close at.

my mechanic thinks its highly likely it is the AAV as he thinks as they get old they get weaker and close faster as a possibility as well as the other type of failure which is they just don't work at all and are jammed either closed or open.

there is another sensor in the AFM unit. called sensor 1.
it measures the incoming air temp.
i have not gone into it apart from reading that it appears to be non replaceable.
guys who have mucked around with L jet for years would know more about it and what it might do.

[wonkipop]

i've just remembered something too about the hose from the plenum to the AAV.

i redid all my vacuum hoses at recommission time.

except for the crankcase vent hose (could not get one) - but it was still ok and doesn't leak.

what i found was that the short hose connecting the AAV that i put on was collapsing because it was such a tight bend. certainly when i had everything hooked up and i revved the engine it sucked in and collapsed completely.

so i took the replacement hose off and put the original back on which was still in good condition. tested for leaks and it didn't leak anyway. the original hose was preformed to the tight curve and does not collapse either from curvature or engine vacuum.

again though, despite the hose not collapsing - i do not have fast idle so the hose is not playing a role in the case of my car.

but if that hose has been replaced and it is constricting then that would inhibit the AAV valve in some cases.

[emerygt350]

You can also do the reverse. You can pull the clean air in hose off the air filter and plug it with your thumb. If the aar is functioning at all your idle should drop even more.

To replicate the aar controlled vacuum leak you can pull any old hose of the plenum (of sufficient size, the decel valve hose would work) and see if your idle increases. That just won't be as definitive as pulling the aar hose from the plenum (or off the aar itself).