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

[emerygt350]

In this case it's probably an emissions measure. You pump extra air into the exhaust (often right near the exhaust port during warm up) to help burn off any extra unburnt fuel. After warm up (in some cars) the air then moves down to the cat. Modern cats mostly don't need this.

[Van B]

I have a ‘99 996 and this pump feeds directly into the manifold. It works like champ. Runs during cold start to achieve the required high idle, which is around 1200RPM, and also kicks on anytime idle needs to be bumped up. So for example if the A/C kicks on, then the secondary air injection pump will kick on to boost idle.
There is also a bypass valve at the throttle body but it’s operation is harder to detect since there’s no noise that makes it obvious.

[emerygt350]

That is so strange. Why would you pump air into a vacuum?

[Van B]

Same as cracking the throttle open. The more you open the throttle, the closer your MAP gets to atmospheric on a naturally aspirated engine. Obviously forced induction engines spend most of the time above atmosphere. But Lambda/oxygen sensors were game changers in that fuel ratios were no longer dependent on measuring intake air in order to adjust fuel mixture. Now cars measure air coming in and exhaust burn coming out and can adjust based on one or both.

[emerygt350]

I suspect it is going into the exhaust manifold unless you are talking about something other than the secondary air pump. I googled it.

[Van B]

I think we’re talking about the same thing but from two different perspectives. The secondary air injection pump is plumbed straight to the manifold on the 996, which means it bypasses the MAF. But since the car has oxygen sensors, it’s still able to adjust the fuel mixture, unlike the 914.
So, if a secondary air injection pump were to be used on a 914, it would have to be piped into the airbox so that the air could be measured by the AFM.

[emerygt350]

I think we’re talking about the same thing but from two different perspectives. The secondary air injection pump is plumbed straight to the manifold on the 996, which means it bypasses the MAF. But since the car has oxygen sensors, it’s still able to adjust the fuel mixture, unlike the 914.
So, if a secondary air injection pump were to be used on a 914, it would have to be piped into the airbox so that the air could be measured by the AFM.

They are entirely different devices. Secondary air pumps into the exhaust manifold. On the 996 it is that way as well. It isn't for idle it is for emissions.
It adds the air after the exhaust leaves the combustion chamber as it is heading out to the cat. That is the upstream circuit. Downstream kicks in after warm up and sends it to the cats on many older cars.


The are also called smog pumps. This is also during open loop so the O2 sensors have nothing to say about it.

https://p-car.com/996/diy/sai/mainpage.html

[wonkipop]

I think we’re talking about the same thing but from two different perspectives. The secondary air injection pump is plumbed straight to the manifold on the 996, which means it bypasses the MAF. But since the car has oxygen sensors, it’s still able to adjust the fuel mixture, unlike the 914.
So, if a secondary air injection pump were to be used on a 914, it would have to be piped into the airbox so that the air could be measured by the AFM.

sounds correct if you were pumping..........
except it might want to leak out the other direction through the intake snorkel rather than push through the flap.

i found an AAV yesterday on a 88 saab in a mates garden graveyard.
i won't be taking it off his car for now - we cut it out of undergrowth to see if we can get it mobile to move it around. if it won't start and move it goes to the wreckers so i'll pull it then.
but..... i know where to look now. fuel injection cars were rarer on the ground in aus in the 80s. the datsuns didn't run L jet of that vintage. there were stacks of these saabs around back in the 80s.




as to emery's observation re air (smog) pumps.
yes the 75 914 2.0s had those.
different kettle of fish than what van is talking about.

on the topic of emissions what i have discovered in old epa material is that the warm up equipment on cars of that era is "emissions equipment".
known as Auxiliary Emission Control Devices. AECD. these were the devices the EPA allowed on cars to let engines warm up or to switch on to prevent engine damage.
the devices could over-ride or turn off emissions equipment (ie an EGR etc).

thats why the nut on the AAV is sealed with a little bit of goop and its hard to take one apart. its an emission device. dictated as tamper proof.

the warm up sequence of these cars post 72 is an EPA dictated time period or distance travelled measure when the car is excempt during the prototype and production line tests from meeting emission levels. after the time/distance period (and the engine is warm) the measuring starts. the EPA did not allow for the engine to come to temp according to a temp gauge, it dictated it ocurred within a certain time and distance travelled after the car was switched on cold. if your car could get to operate temp before the measuring started, bonus, but if it did not then whatever it was spewing out the tailpipe got measured as part of the test,.....bummer.

the EPA certification testing by manufacturers was done on a rolling road.
by the manufacturer at their factory.

[wonkipop]

by the way, if you read the factory manual and find yourself puzzled by the way 68F keeps coming up for testing various little items, thats where it comes from.

its the EPA test min temp. so you measure electrical resistance etc or whether something opens or shuts at 68F. instruction is typically to discard the part and fit a new one. its all emissions.

i was thinking about the emission warranty that was offered on these cars back then.
50,000 mile or 5 years. a smart cookie owner could have really had fun with that one.
you could just about call everything supplying fuel/air into the engine an emissions device and get them replaced under warranty. most folks would not have realised.
(IMG:style_emoticons/default/beer.gif)

anyway. the epa test dictated to manufacturers in 73/74 has the time period imbedded in it for the warm up sequence to run. if we can find that. - thats about how long the AAV opens for and the ECU runs its enrichment.

in my view, if you have a healthy sensor 1 and 2 (intake sensor, cht sensor) and a functioning ECU (those things are military grade spec and could survive on mars) then i believe that side of things is covered. the only thing that can upset what the sensors and the ecu is commanding is the AAV when it comes to warm up. (remembering this car of Vans and mine run just fine and dandy once warm).

[Van B]

I think we’re talking about the same thing but from two different perspectives. The secondary air injection pump is plumbed straight to the manifold on the 996, which means it bypasses the MAF. But since the car has oxygen sensors, it’s still able to adjust the fuel mixture, unlike the 914.
So, if a secondary air injection pump were to be used on a 914, it would have to be piped into the airbox so that the air could be measured by the AFM.

They are entirely different devices. Secondary air pumps into the exhaust manifold. On the 996 it is that way as well. It isn't for idle it is for emissions.
It adds the air after the exhaust leaves the combustion chamber as it is heading out to the cat. That is the upstream circuit. Downstream kicks in after warm up and sends it to the cats on many older cars.


The are also called smog pumps. This is also during open loop so the O2 sensors have nothing to say about it.

https://p-car.com/996/diy/sai/mainpage.html

Ok so we’re not talking about the same thing.

[emerygt350]

by the way, if you read the factory manual and find yourself puzzled by the way 68F keeps coming up for testing various little items, thats where it comes from.

its the EPA test min temp. so you measure electrical resistance etc or whether something opens or shuts at 68F. instruction is typically to discard the part and fit a new one. its all emissions.

i was thinking about the emission warranty that was offered on these cars back then.
50,000 mile or 5 years. a smart cookie owner could have really had fun with that one.
you could just about call everything supplying fuel/air into the engine an emissions device and get them replaced under warranty. most folks would not have realised.
(IMG:style_emoticons/default/beer.gif)

anyway. the epa test dictated to manufacturers in 73/74 has the time period imbedded in it for the warm up sequence to run. if we can find that. - thats about how long the AAV opens for and the ECU runs its enrichment.

in my view, if you have a healthy sensor 1 and 2 (intake sensor, cht sensor) and a functioning ECU (those things are military grade spec and could survive on mars) then i believe that side of things is covered. the only thing that can upset what the sensors and the ecu is commanding is the AAV when it comes to warm up. (remembering this car of Vans and mine run just fine and dandy once warm).

Yeah, exactly. I have learned through my time fixing what others had done to early injection systems that you can often tune a car to be fine at warm up by bypassing/twiddling with something and until all of it is correct the car isn't actually doing what it is supposed to. On my Ford CFI motor I spent years figuring out all the little things previous owners had done to get it to run well at normal operating temps (and fixing them). On my 914 I have found many ways to hide problems. CHT mods and leaks to hide rich conditions, retarding or advancing timing to address the idle issue your vacuum leak is causing, rerouted vacuum lines to address broken components, etc. Hell the car ran fine warm when I got it and it had three different injectors in it. That said, I am sure this is the AAR but it is good to know all of it is actually doing what it should be. As everyone has said, there is no feedback so it has to work like clockwork.

[wonkipop]

by the way, if you read the factory manual and find yourself puzzled by the way 68F keeps coming up for testing various little items, thats where it comes from.

its the EPA test min temp. so you measure electrical resistance etc or whether something opens or shuts at 68F. instruction is typically to discard the part and fit a new one. its all emissions.

i was thinking about the emission warranty that was offered on these cars back then.
50,000 mile or 5 years. a smart cookie owner could have really had fun with that one.
you could just about call everything supplying fuel/air into the engine an emissions device and get them replaced under warranty. most folks would not have realised.
(IMG:style_emoticons/default/beer.gif)

anyway. the epa test dictated to manufacturers in 73/74 has the time period imbedded in it for the warm up sequence to run. if we can find that. - thats about how long the AAV opens for and the ECU runs its enrichment.

in my view, if you have a healthy sensor 1 and 2 (intake sensor, cht sensor) and a functioning ECU (those things are military grade spec and could survive on mars) then i believe that side of things is covered. the only thing that can upset what the sensors and the ecu is commanding is the AAV when it comes to warm up. (remembering this car of Vans and mine run just fine and dandy once warm).

Yeah, exactly. I have learned through my time fixing what others had done to early injection systems that you can often tune a car to be fine at warm up by bypassing/twiddling with something and until all of it is correct the car isn't actually doing what it is supposed to. On my Ford CFI motor I spent years figuring out all the little things previous owners had done to get it to run well at normal operating temps (and fixing them). On my 914 I have found many ways to hide problems. CHT mods and leaks to hide rich conditions, retarding or advancing timing to address the idle issue your vacuum leak is causing, rerouted vacuum lines to address broken components, etc. Hell the car ran fine warm when I got it and it had three different injectors in it. That said, I am sure this is the AAR but it is good to know all of it is actually doing what it should be. As everyone has said, there is no feedback so it has to work like clockwork.

all true.
but i don't have one of those cars thats been worked over and fooled with.
its purty much all ridgy didgy.
and mechanic and i confirmed all the sensors were fine 18 months ago.
its running absolutely original injectors (a full matching set of NOS off a guy in arizona 18 months ago, all bagged sealed from factory. its the same exact injectors that go in a beetle convertible). everything is schmick on that side of things.

what i do not have is a set of operating cooling flaps. admittedly.
and what i do reckon i have might be an AAV that there is no real test for, other than, is it open and does it close. which i did check. but thats pretty crude as a check.
what i have been searching for hard is finding out anything with a bit more detail on that AAV. there is nothing.

but what i do know now is it is officially an "emissions device".
admittedly an AECD, but one nonetheless.
which might explain why you just cannot get info on it.
its not meant to be adjusted or fooled with under the terms of the original emissions warranties (and as dictated by the EPA).
rather its meant to be thrown away and replaced at 50,000m or 5 years.

but of course we idiots are trying to keep these things going after half a century.

(IMG:style_emoticons/default/smile.gif) (IMG:style_emoticons/default/beerchug.gif)

at least i know where i think i can find some of these AAVs easily in those SAABs.
it looks right. but i have to get one off and must make sure. elec connections etc.
i don't want to tear the one apart on my 914.
but i am happy to rip into some sacrificial ones if i can get hold of a few and experiment - assuming they will hook up ok. sometimes you get tripped up on the electrical connection or the hose size......but it sure looked like i was staring at a AAV that looked the same on the outside.

i did the same thing about 12 months ago when i bought a couple of old roller cell bosch fuel pumps from a VW guy in texas. i didn't care if they went. paid $20.00 for each of them. i wanted the parts and i wanted one as a tear down exercise before i ripped into two "good" pumps i had here (mine ran but leaked fuel). i managed to rebuild two original roller cell pumps that way. (motors were not worn out in them, all the seals were leaking). to fix the seals in a otherwise perfectly good old fuel pump you have to go all the way in and take them all apart.
its supposed to be impossible. it can be done. those old pumps are great because they deal with the hot location under the engine better than modern (in line or linear turbine) pumps. and i want to keep the pump where it was. call me a geek for doing that when everyone shifts them up front. but mine worked fine. i had no vaporization problems years ago. it was shifted just far enough in 74 to not get into too much trouble in original location. i also hate the idea of running high pressure fuel line through the cockpit (inside the car) which is what the 75 and later cars do! ?

as a result of that crazy exercise i managed to fix up two of the same type old pumps for my mates mercedes benzs. they were just leaking fuel, but fine otherwise.

[emerygt350]

My pump is still down there as well, not sure what I will do when I get steel lines. Probably go up front but I don't want to run the wires.

You may have better luck going to Saab for your AAR
I find the stock one in my car really annoying. You need it for the first couple minutes definitely but I wish it would just cut out after that even if it doesn't run perfectly for a little while yet. Instead it just keeps on going till everything is perfectly warm. I bet my heating element is weak and it needs the engine warmth to finish the job.

[Van B]

Here’s an update on what I’ve got cooking:
I cleaned out eBay for original Bosch injectors. I’ve bought seven NOS 0280150112 injectors. I’ll send all of them out to get dynamic flow testing and see if I have four that can make a matched set. The other three I will sell on here. @StarBear I see that you bought a couple recently so, if you want to complete a set let me know.
Also, I bought a new thermo time switch for a 924/944. The research I’ve done confirms that this part number also traces to the 912E. Not sure why nothing connects back to our 914, but I will compare them with a multimeter at various temps and see what we get.

Reasons for these endeavors are that I noticed a miss for a couple minutes after start on one of my recent attempts. My hypothesis is that if an injector is firing all Wonkipop (lol) then fuel could just be jetting onto the cylinder and not firing until temps get high enough to vaporize the fuel.

Further, I only get a couple of seconds of high idle when the engine starts which is almost certainly thanks to the CSV. So, maybe the thermo switch is not behaving correctly and telling the CSV to run for it’s max time of 20sec.

The test procedure for the 914 is closed below 68F or open above. However, the 912E manual gives varying levels of resistance at progressively warmer temps.

We’ll see if any of this bears fruit, but like I said before, I have no clear direction so it’s all trial and error from here.

Van

[StarBear]

Here’s an update on what I’ve got cooking:
I cleaned out eBay for original Bosch injectors. I’ve bought seven NOS 0280150112 injectors. I’ll send all of them out to get dynamic flow testing and see if I have four that can make a matched set. The other three I will sell on here. @StarBear I see that you bought a couple recently so, if you want to compete a set let me know.
Also, I bought a new thermo time switch for a 924/944. The research I’ve done confirms that this part number also traces to the 912E. Not sure why nothing connects back to our 914, but I will compare them with a multimeter at various temps and see what we get.

Reasons for these endeavors are that I noticed a miss for a couple minutes after start on one of my recent attempts. My hypothesis is that if an injector is firing all Wonkipop (lol) then fuel could just be jetting onto the cylinder and not firing until temps get high enough to vaporize the fuel.

Further, I only get a couple of seconds of high idle when the engine starts which is almost certainly thanks to the CSV. So, maybe the thermo switch is not behaving correctly and telling the CSV to run for it’s max time of 20sec.

The test procedure for the 914 is closed below 68F or open above. However, the 912E manual gives varying levels of resistance at progressively warmer temps.

We’ll see if any of this bears fruit, but like I said before, I have no clear direction so it’s all trial and error from here.

Van

@Van B Terrific; I have two pairs that seem the same but are different colors (maybe VW vs Bosch?). Will check and get back to you.

[Van B]

@StarBear look at the number on the side of the injector. It will be molded into the top half 90deg offset from the connector. As is so often the case, we can thank @JeffBowlsby for cataloging this info:
http://www.914world.com/bbs2/index.php?sho...&hl=neihoff

0280150112 is the factory injector. But there are three other injectors that are the same injector but with different hose options. Of those three, you would want to have 0280150116, the long hose you can trim to fit. The other two are short hoses.

[StarBear]

@StarBear look at the number on the side of the injector. It will be molded into the top half 90deg offset from the connector. As is so often the case, we can thank @JeffBowlsby for cataloging this info:
http://www.914world.com/bbs2/index.php?sho...&hl=neihoff

0280150112 is the factory injector. But there are three other injectors that are the same injector but with different hose options. Of those three, you would want to have 0280150116, the long hose you can trim to fit. The other two are short hoses.

@Van B Here are the ones I have. The original in the car are 112 units, with a gray/beige connector. The two spares are also 112 units, but with a blueish connector. See photos.
Yes, would love another pair of tested, proven injectors as SOME time in the future my originals WILL fail. Awesome!
Current:
Spares:

[Van B]

Yeah, connectors are beige but the injectors are blue-green. I noticed that on my car too.

[wonkipop]

Here’s an update on what I’ve got cooking:
I cleaned out eBay for original Bosch injectors. I’ve bought seven NOS 0280150112 injectors. I’ll send all of them out to get dynamic flow testing and see if I have four that can make a matched set. The other three I will sell on here. @StarBear I see that you bought a couple recently so, if you want to compete a set let me know.
Also, I bought a new thermo time switch for a 924/944. The research I’ve done confirms that this part number also traces to the 912E. Not sure why nothing connects back to our 914, but I will compare them with a multimeter at various temps and see what we get.

Reasons for these endeavors are that I noticed a miss for a couple minutes after start on one of my recent attempts. My hypothesis is that if an injector is firing all Wonkipop (lol) then fuel could just be jetting onto the cylinder and not firing until temps get high enough to vaporize the fuel.

Further, I only get a couple of seconds of high idle when the engine starts which is almost certainly thanks to the CSV. So, maybe the thermo switch is not behaving correctly and telling the CSV to run for it’s max time of 20sec.

The test procedure for the 914 is closed below 68F or open above. However, the 912E manual gives varying levels of resistance at progressively warmer temps.

We’ll see if any of this bears fruit, but like I said before, I have no clear direction so it’s all trial and error from here.

Van

the old 68F, wonder where thats coming from hey?

@ Van - you can go for any one of the injector options on mr. b's website chart.
similar chart from a bus expert mr. r atwell. there are three counting the real ones.
think the other two are short and long hose. for bus and for 412/411 from memory.
we run the same ones as beetles from 79 or something like that. thats how i got a set, bought them off a guy in arizona who had them in his cupboard for years for his beetle.

then remove the incorrect hoses if you get the non exact injectors and buy a set of correct hoses from 914 rubber.
the hoses need to curve just right as they support the fuel rail. suspend it in mid air more or less.

[Van B]

Where can I get a proper fuel filter for my car? I ordered the round Mahle filter from FCP Euro, but it looks pretty small. I haven’t pulled the tank yet so, I’m only guessing right now. But I figured I’d trust my instinct and ask you guys.