1974 1.8L engine fast idle then stalls, Fuel injection issues Options

[wonkipop]

yours might be alright? if you got 1.7 k ohm.
i guess it depends on how cold it is there currently where you live.
at 68 F it says you should get 2.5 K ohm.
and progressively less for colder temps.

Think you have it backwards...
With NTC thermistors resistance decreases as temperature increases.

I will slope a NTC sensor. Put it in freezer, record resistance, refrigerator, record, room temp, record, hot tap water, record, boiling water, record.

I want the slope between each point to be similar for all...

Sometimes you will find a sensor drops out at a certain temperature.

yeah you are right.
i'm backwards on that.
another naturally dyslexic moment. (IMG:style_emoticons/default/biggrin.gif)

[tshih914]

yours might be alright? if you got 1.7 k ohm.
i guess it depends on how cold it is there currently where you live.
at 68 F it says you should get 2.5 K ohm.
and progressively less for colder temps.

Think you have it backwards...
With NTC thermistors resistance decreases as temperature increases.

I will slope a NTC sensor. Put it in freezer, record resistance, refrigerator, record, room temp, record, hot tap water, record, boiling water, record.

I want the slope between each point to be similar for all...

Sometimes you will find a sensor drops out at a certain temperature.

I posted a bunch of videos and shorts on my YouTube channel @Pfan12000 .
link here: https://studio.youtube.com/channel/UCmLvtTxokU7diByRQaSm46Q

[Van B]

I’m sorry, but it seems like everyone is forgetting this car was unceremoniously parked for years. I know without a doubt the injectors are in bad shape.

Remember, I bought 7 NOS Bosch injectors and had them all dynamically tested, 2 failed for spray bad spray pattern and 1 for low flow in part throttle conditions. So, if a new injector in a box can go bad, why not one that was just parked full of fuel?

This racing idle is a red herring IMO.

[Van B]

After watching the video of the car running, it’s entirely possible that the AFM is incorrectly calibrated. Spring could have too little tension and is allowing the flapper to open too much at idle. But also, the injectors could be dumping fuel and you’re just choking it down by clamping the AAV.

Regardless, you have yet to confirm the timing, or assess the plugs after running the engine.

[wonkipop]

I’m sorry, but it seems like everyone is forgetting this car was unceremoniously parked for years. I know without a doubt the injectors are in bad shape.

Remember, I bought 7 NOS Bosch injectors and had them all dynamically tested, 2 failed for spray bad spray pattern and 1 for low flow in part throttle conditions. So, if a new injector in a box can go bad, why not one that was just parked full of fuel?

This racing idle is a red herring IMO.

well, it is and it isnt. a herring of the red variety.

its certainly one of his problems.
and should be eliminated.
unless he likes just sitting around in it with it yelling at 3000 rpms stationary! (IMG:style_emoticons/default/smile.gif)

eliminated - before he gets to the real one.
which is why won't it take throttle.

which may well be what you suggest.
likely either fuel. or ignition.
and i'd start with fuel.
if it isn't then.........

been my experience that injectors are cactus completely after a long layoff.
and if not spraying properly would still accept some application of power?
not just die totally. but fuel pressure on throttle demand is in the same league.
i can see how that might happen if there is a troublesome kink in the fuel lines somewhere. recent work involved renewing them all? potential there?
that will drop your injectors out - no problem.
his fp is fine at idle but it has not been examined in other states.
was going to get to that.

---

what will become evident is once these large metered (at present uncontrolled) air routes are tamed any unmetered air leaks will make their presence felt as he tries to lower the idle. they will cause it to lean out. and if they are there they will need to be eliminated.
helps to be able to get the idle down to do the timing!!!!. kind of a catch 22.

then its the throttle problem. which you can start to trouble shoot properly.

just the way i do things.

might be worth investment in new injectors. (IMG:style_emoticons/default/smile.gif)
at least you can rustle some up for a reasonable price in the USA.
be good if thats all it was. but i am not sure i would jump to that just yet.
but i agree its probably on the cards.

so far it looks like most of his stuff works aside from AAV and decel.
maybe a question mark on CHT but its kind of OK.
enough for this exercise.


------

i can't seem to get his youtube link to work to listen to the engine.

interesting observation you make @Van B

i think that is what i was beginning to think about before in prior post.
about seeing if it would carefully take throttle if idle revs could be brought down.
was it something to do with where the potentiometer was at on the AFM driven by the flapper and was this in the right place?

[technicalninja]

just quickly looked through this thread.
I have UBER experience with the version of this fuel injection that Nissan used in the 75 and up Datsun Z cars.

I traded my first rat box 914 for my first Z car and its been nearly 40 years between 914s but I've ALWAYS had a 1st gen Z car. I have 10K lbs of stripped Z car parts...

Datsuns did not have decel valves. They used dash pots on the throttle linkage for the same reason.

Everyone has given good advice but it looks like there are "too many cooks" in the kitchen for me...

It also looks like the original poster is not experienced in fuel injection diagnosis and trying to help across keyboards can be difficult.

I'd base line the car first.
Pull plugs, inspect and do compression test. record numbers.
Check ignition stuff over; cap, rotor, wires, points if still in use.
I'd test both the vacuum advance/retard and the mechanical advance in the distributor.

what is the age of the fuel in the tank?
If it's over 1 year old completely drain tank and replace with fresh.
A new fuel filter should always be installed if a fuel poisoning has occurred.

Any gas with ethanol in it is complete trash after 1 year and suspect bad after 6 months.

Test fuel pressure with a gauge and a vacuum tester hook to regulator. Appling vacuum should decrease fuel pressure. Z numbers were 36 no vacuum and when vacuum is applied the regulator keeps a 36 psi difference between manifold vacuum level and the injector.
15" of vacuum equals a drop of 7.5 psi,
20" of vacuum equals a 10 psi drop and so on.
When an engine is running properly and has good manifold vacuum at idle you can see 24-26 psi on the gauge idling shoot up to 34-35 psi when you snap the throttle open suddenly.
I doubt the OP has a good stable vacuum signal to work with right now...
Make sure you can see 36 psi when running the pump without the engine running.

Compression, fuel quality and pressure, ignition all check out...

I do what R-Towle suggested and get rid of all of the vacuum except the main boot between AFM and T-body, the vacuum line to the fuel pressure regulator, and the vacuum line to the distributor advance side.

I'd test and adjust the TPS. I just tested the one off my 75 914. There are 3 pins on the TPS unit itself. The outer pins never have continuity and when the throttle is shut you will see continuity between the center pin and one of the outers. Open throttle it goes to infinity on the meter (no continuity) and above 80% travel (wide open) you will get continuity between the center pin and the other side. You adjust the closed throttle side only. You adjust it to just gain continuity when closed.
The Datsun TPS works exactly like the Porsche except the Datsun is adjustable via slotted mounting holes and the Porsche is not. You could slot the mounting holes if yours needed adjustment.

Biggest thing with the TPS... you should be able to disconnect it and the car should run ok without it in the system. The idle will be affected but it will not be high, it will hunt and tend to be lower.

Oh, continuity is tested on a meter. You can have a beep that will often happen when you reach 0 ohms but trusting the beep is shooting yourself in the foot.
Set your DVOM to resistance (ohms) and look at what it reads with the leads disconnected. This is infinity and often will read O.L (over limits).
Touch the leads together and you will get a very low numerical reading like 0.02 this is continuity. Most DVOMs have a zero button that will take that continuity reading to absolute zero for extremely low resistance checks (which you don't care about right now)
Now hold a lead in each hand, you will get a different reading usually in mega ohms "M". You just checked resistance across a piece of meat. Across a human you will never see infinity and you will never see continuity.

FI diagnosis is a step by step process and if you miss something early in the process you will drive yourself crazy.

I self-taught myself in 1982 with a basic theory book much like the one Woki posted.
It took a while before it all made sense and I can learn faster than anyone I know.

I'm in agreement with Van B who is spot on. I would want to be able to hold the throttle slightly open and acheive running at 1500+ rpm with proper responce to throttle inputs before I ever started working on an idle problem.

Even if the car will not idle. I would expect to be able to drive it around in a fairly normal manner before I started nit-picking anything.

The whole closing the entrance to the airfilter off should have killed the car bigtime.

My money is on big vacuum leak, bad fuel, poor injector patterns (the ethanol jacks with injectors bigtime!).

Hope this helps
I type too much
Rick

[wonkipop]

@tshih914

yeah that link is making me sign into google or something?
really weird. won't just link straight through to you tube.

EDIT

ok i got in to the film. did a search of your channel name and got it.

very interesting.
i am going to send that link to mike, our mechanic.

(IMG:style_emoticons/default/beerchug.gif)

[technicalninja]

And wait, there's more...

I was fighting bad AAVs back when they were 10-15 years old. I can't imagine one making it to 40...

All the AAVs I messed with were Datsun Z stuff but it looks EXACTLY what we have on the 914 and works in the same way.

The bi-metallic strip which makes them close properly get old with age (15 years here) and doesn't work properly.
The Datsun ones could kinda be adjusted by loosening the pivot bolt and jacking with the internal shutter but that never worked very well or very long.
The best solution was to purchase a new one and they were expensive and hard to come by 25 years ago...

You could always just leave it out and plug its connection. Cold idle sucked and you would have to nurse the car to temp but it wasn't a deal killer, just an annoyance.

They DID NOT require engine temperature to close. The heating element (which is what the electronics are for) was powerful enough to close a frozen one in about 5 minutes.

Yep, I use my refrigerator/freezer for many different automotive uses.
I currently store my POR15 in the shop fridge as it extends the shelf life 300%

[Van B]

Regarding the AAV heating element. Based on your experience, I’m betting the rebuilt units don’t have the same elements as the original. Probably cheap Chinese parts…

[wonkipop]

@Van B

i watched that film again a couple of times.
and i'm mindful of your injector views.

only my experience is they just jamb up.

its a long weekend down here (but i'm working regardless, my lot in life due to the stupidity of my choice of profession made at age 17 (IMG:style_emoticons/default/biggrin.gif) )
mike will be sitting back on a lounge chair by a river bank and if he has iphone reception will partake of the video in between catching fishes.

but here is a scenario.
and it involves injectors.

i know my 914 would purely run off the cold start injector.
this was a functioning cold start injector.
it ran for about 10 seconds. quite vigorously. while it ran.
this was our first attempt to start mine officially after 16 years.
after all the gizmos had been checked by me that i have asked our friend to check.

after it died each time after three goes mike pronounced the injectors "farked".
made the sign of the cross and instructed me to secure "new" ones from the promised land. which i duly did.

the original main 4 injectors were not running at all.
we pulled them and tested them. corroded shut.
this was despite 3 weeks earlier having got them cleaned and tested.
in three weeks they reverted to non operational, non recoverable from coma state.

but the cold start injector was working. correctly. and boy it could run the engine on its own. until it switched off. exactly as it was meant to do despite the passage of 50 years since it was born and despite being asleep for 16 years.

do we have a scenario here where this baby is running off a cold start injector that is malfunctioning and not closing off? just keeping on keeping on and squirting a vile unatomised stream into the intake plenum.

then when you gas it and the main injectors really do need to work - narthing.
because they are literally not working? leans out. all over.

then you close the throttle and it comes back to life on its dribbling cold start injector.

i don't know.

------

i'd pull those injectors.
all of them.
cold start too.
and just see what they are doing.
point them at a bucket and crank it.

and i'd check the plugs.
like you have been harping about.

it was pretty informative to watch that film he posted.

[technicalninja]

I didn't know "rebuilt" were even available...
They weren't 25 years ago.

I got my current 914 with a brand new progressive 2 barrel installed by the PO incorrectly. The choke was still tight, and he had no power wire run to it...

I killed the tension and the engine magically ran better.

The entire FI came with the car in boxes. I think I have all of it but I'm hoping you guys can help me identify what's missing.

I'm going to test pulse patterns on the injectors just to make sure they still work at all and then send them off to an injector cleaner as I don't own one to the fancy back-flushing test sets.
I'm not even going to try and run them before a professional cleaning.

I got a NOS fuel pump from 914Sixer and this car has a newer FPR on it now.

I'm going to change the plastic lines BEFORE I'm ever going to push modern gas at pressure through them. They scare the hell out of me...

I held a 914 throttle body for the first time in my life tonight as I was checking how the TPS worked before my first novel above.

I may have a bad throttle body as it does not auto return to the closed position. It doesn't appear to have any spring tension on it at all. It looks like it would cause all kinds of high idle issues the way it is now.

Compared to a Datsun throttle body this thing SUCKS!
It's TINY and it doesn't have a throttle stop screw. The air bypass is crazy. The TPS is non-adjustable, and the mounting flange/gasket/rubber cup looks like a sealing problem in the making.
I am NOT IMPRESSED!
I may need one of the pups anyway and I'm going to start looking for a bus throttle body as I believe I've read that it's a bit bigger.

This thing looks like it should be on a 1000 cc engine, not a 1800...

[wonkipop]

@technicalninja

i'm digesting your comments.
experience on J fuel injection totally relevant.
nippon EFI was faithful J implementation of krautrock systems.

[wonkipop]

@technicalninja - yeah i just read through your big post up above.
i can see why you call yourself a ninja now. (IMG:style_emoticons/default/biggrin.gif)

his big problem is he can't get it down to 1500+ to start playing with the throttle.

thats what i was angling at.

just to somehow get it down to there and then gently play with the throttle.

but it seems like he can't get it down to there.

he has got a massive air leak.
but there are two sorts.
metered.
unmetered.
and you do need to separate them.

most people just think of air leaks as air leaks.
but each of the two types produces the opposite effect.

when i say metered air leak, i mean a part of the system that goes via the same route as the throttle.

its real fun getting your head around L jet.
its actually far more logical than carbies.
and its so vintage german. like listening to kraftwerk play music on home built prototype electronic instruments. whats not to like. (IMG:style_emoticons/default/beerchug.gif)

PS
thanks for the tip on POR15 and the fridge.
i'll pass that on to mike.
he is always whinging about POR 15 going off. lids sealed with tape etc.
not sure i will want to drink the chilled water we also keep in the fridge in the workshop if he does. (IMG:style_emoticons/default/biggrin.gif)

[technicalninja]

But wait, there's more...

I've found huge masses of fuel deposits in gas tanks that have gone bad.
I've got a parts donor 99 Miata right now that you cannot open the fuel cap without vomiting...
I'm not going to clean it, just throw it away with the car.

It's a real good idea to actually look down into a fuel tank that's been poisoned.
I found what looks like an underground cavern with stalactites and stalagmites growing from fuel "fungus" in the tank. this was in a fuel injected Fiat Spider (same L-Jetronic stuff as 914s and Z-cars) that had sat 3.5 years, and this was before ethanol...

A badly poisoned tank must be either cleaned out of replaced.
One of the members on this forum makes new replacements.
I'd contact him for a new tank.
I'd pay 3 times what a cleaning cost to go new over cleaned.
Last tank I had cleaned cost $150.00 years ago.
I wonder if you can still get tanks cleaned?
All the radiator shops have gone out of business...

[wonkipop]

But wait, there's more...

I've found huge masses of fuel deposits in gas tanks that have gone bad.
I've got a parts donor 99 Miata right now that you cannot open the fuel cap without vomiting...
I'm not going to clean it, just throw it away with the car.

It's a real good idea to actually look down into a fuel tank that's been poisoned.
I found what looks like an underground cavern with stalactites and stalagmites growing from fuel "fungus" in the tank. this was in a fuel injected Fiat Spider (same L-Jetronic stuff as 914s and Z-cars) that had sat 3.5 years, and this was before ethanol...

A badly poisoned tank must be either cleaned out of replaced.
One of the members on this forum makes new replacements.
I'd contact him for a new tank.
I'd pay 3 times what a cleaning cost to go new over cleaned.
Last tank I had cleaned cost $150.00 years ago.
I wonder if you can still get tanks cleaned?
All the radiator shops have gone out of business...

sh$t
the horror stories about fuel that you guys have.
whats going on with the petroleum situtation in the USA.
the home of texas tea.
so far here we are not experiencing those problems.
but we did have a right of centre government in coalition with the farmers party.
and those guys are sticklers about fuel quality.
tractors = fuel = food.
i'm not so sure about whats going to happen now.
the opposites are in power.
this is not a poltical statement for the admins.
merely an observation about govt. fuel standards regulation.
and fear of what might be ahead of me.

[technicalninja]

@technicalninja - yeah i just read through your big post up above.
i can see why you call yourself a ninja now. (IMG:style_emoticons/default/biggrin.gif)

Technicalninja is a pretentious name for someone to call himself.

I did not name me...

My shop buddies did in 1991 long before the internet was a thing.
I got my "handle" the old fashion way, voted on by my circle of friends...

WITHOUT MY CONSENT!

Being called "super-tech" or "Mr. Goodwrench" is an insult in the automotive world.

'Hey guys, here comes SuperTech, lets see what he can mess up today" displays the usual use of a pet name in the shop.

The story of my naming will be in another post but when I know something I'm usually pretty good at it...

[wonkipop]

@technicalninja - yeah i just read through your big post up above.
i can see why you call yourself a ninja now. (IMG:style_emoticons/default/biggrin.gif)

Technicalninja is a pretentious name for someone to call himself.

I did not name me...

My shop buddies did in 1991 long before the internet was a thing.
I got my "handle" the old fashion way, voted on by my circle of friends...

WITHOUT MY CONSENT!

Being called "super-tech" or "Mr. Goodwrench" is an insult in the automotive world.

'Hey guys, here comes SuperTech, lets see what he can mess up today" displays the usual use of a pet name in the shop.

The story of my naming will be in another post but when I know something I'm usually pretty good at it...

i'd call ninja a compliment.
down here it would be.

when i was a kid we used to get these J kiddies shows on aus tv.
one of them was about these spooky ninjas who could leap backwards and do stuff.
i spent my whole childhood along with my mates pretending to be one.
trying to walk backwards and chuck ninja spinning star daggers at each other. (IMG:style_emoticons/default/biggrin.gif)
thats one thing about australia where it was in advance of the USA.
we established cordial post war relations with Japan before anyone else in the pacific.
despite WW2 and all its horrors we had iron ore to sell.
and J needed it.
its a curious thing australia's relationship to Japan.
we did an exchange with J TV stations in the 60s.
they got skippy the bush kangaroo.
we got ninjas.
we came out on top in that deal. (IMG:style_emoticons/default/beer.gif)

[wonkipop]

here you go mate. @technicalninja

i found it.
you can find anything on youtube.

phantom agents. aussie kids were obsessed with this circa 1965.
we would wear plastic breakfast bowls on our heads trying to copy this stuff.

https://www.youtube.com/watch?v=t2_tMhgisd8

more conservative kids were into SHINTARO.
he was your typical historical samurai figure.
but no way was he a ninja.

phantom agents were the sh$t.
you need to get into the phantom agent mindset to crack L jet.
no use being an american/aussie trying to tune a carby!

shintaro. (not really my scene when i was 7 years old).

https://www.youtube.com/watch?v=-eVZHgBkMWI

back to krautrock fuel injection.
these diversions are important.
there is lots that can screw up in L Jet of a mechanical nature.
which @Van B reminds us of.

(IMG:style_emoticons/default/beerchug.gif)

[Geezer914]

Not to be redundant, but did you do a smoke test and check the intake runner gaskets???

[tshih914]

My fuel is OK as I have been very mindful as a chemist and have used fuel preservatives like Marine Stabil and I've replaced the plastic lines with stainless steel ones and installed all new fuel hoses. It is very possible my injectors are not working will have to pull them and test.

As far as our future use of fossil fuels and fuel quality concerns, those farking A-holes in power around the world (especially in USA) have been bought and corrupted and compromised by China CCP to force everyone to join the cult of Climate change and Marxism.

The new breed of electric cars are soulless and boring would much rather play with our old toys.

I have posted a short video on my channel showing the current resting state of my AFM showing a slight gap at the door which I was closing using a flat blade screwdriver. Is that gap (2-3mm) supposed to be completely closed in a correctly adjusted AFM?