924Board.org

[Riggard]

That seems to point to the WUR or the cold start valve. Given that you already had issues with the WUR, I'd start with that.

I assume you did test the war with power on the heating element?

[coup85]

I found some small dirt over the diaphragm, cleaned it, and now all measures are spot on. I haven't tried the start yet, but I don't expect a clean start, as the mixture was manually adjusted by me to compensate for the faulty WUR. I need to find a shop to help me adjust it back again now that everything seems on track.


@Riggard, I tested the CSV some time ago, as it was kind of simple to do, the AAV too, and both worked fine. In any case, if the cold start is still bad, I'll check again. Thank you for your help!!!
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924 - 79'

[Riggard]

Sounds like you're getting somewhere the basic mixture can also be tuned by sound. Turn the screw lean (i think ccw) until the idle becomes erratic, then twist until it becomes smooth again and try to set it just where the smooth idle starts.

[coup85]

Well…funny enough…since I still had the CIS rig hooked up, I ran one last check on the WUR… and it’s leaking again. Not dramatic, but it won’t seal. The cleaning seemed to help for a bit, but after a few cycles it came back. I disconnected the WUR return to watch it directly and there’s a tiny seep when it should be closed. Cold control pressure is still on the high side (about 2.0–2.2 bar). Feels like WUR rebuild time!

PS: Does anyone have a good source for the inlet micro-screens?
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924 - 79'

[coup85]

Because of the type of problem I'm dealing with, do you think the basic www.missingparts.de WUR-repair kit would be enough, or am I dealing with something else?
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924 - 79'

[coup85]

As a side note: the people from missingparts.de are the best, amazing client service!
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924 - 79'

[Riggard]

looks like a very complete kit. It doesn't contain the intake mesh, but idk about that; never had to remove it.

[Raize]

Make sure all the mating surfaces on the fuel cell are clean and flat too without any scratches. I remember having to sand at least one of mine.

[coup85]

I’m going a bit crazy with this. I finally got the WUR working properly and pressures are now where they should be, but after still having problems with the start and idle, I’ve noticed something odd around the mixture adjustment screw area on the air sensor housing.

When I spray carb cleaner there, the revs go up, and when I did a vacuum test I could actually see a little vapor coming out of that spot. Looking at the PET and Rose Passion diagrams, there seems to be a small plug (“stopper blue” / “plug for air sensor housing”) listed for the 924 NA, but on my car, that place looks open.

Has anyone else run into this? Should that opening really be sealed from factory? Could I be missing that plug?

I'm not sure if it's messing with the mixture…
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924 - 79'

[morghen]

k-jet is sometimes stubborn and difficult to get running properly, even if you bring it in the specs. Been there, done that.

Let me know when i should prepare that EFI kit
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Supercharger and EFI kits
https://www.the924.com

[coup85]

Unless you are giving them away for free I’m afraid it's not an option right now

Jokes aside, my idea has always been to keep it original.
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924 - 79'

[coup85]

Update: after a little research, it appears that the plug was for protection, as the air coming from that hole passes through the plate, missing the filter, but not causing a leak by itself, as is metered by the sensor plate. So, time to check somewhere else!
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924 - 79'

[Raize]

[coup85]

I have these issues right now:

-Cold start: it takes 2-3 long attempts to start without using the throttle. Once it does start, the idle is low, approximately 500 RPM.

2. When the engine heats up, the idle increases slightly to around 700 RPM. However, if I give it throttle, the RPM rises to 1000-1100 and remains there.

3. Hot start: the engine starts reasonably well but has a low idle of 700-800 RPM. Again, if I apply some gas, the IDLs increase to 1000-1100. This is kind of annoying as I don't know how or when to set the idle.

Extra: Power Loss, there is a noticeable lack of power in the RPM range of 1000-2000.

Regarding the wideband sensor, my main concern is not wanting to drill a hole in the exhaust for installation. I'm not sure if there is an alternative method to use it. I did try to find a garage with an analyzer to help me check the mixture, but it's kind of impossible nowadays; no one uses them anymore! However, I found a shop that I believe can assist me, and I plan to call them on Monday.

PS: I forgot to say that despite the WUR being inside the margins, it is on the top one (control pressure 1.8 bar at 24ºC/75,2º F), also, the AAV it's working fine too.
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924 - 79'

[Raize]

Needing to rev it to reset the idle is normal - there's no idle control on these.

Try adjusting the mixture control screw on the fuel distributor. The position which gives the fastest RPM is around 12.5 AFR.

So if you turn the screw clockwise and the revs drop (after removing the allen key and giving it a quick rev to reset the idle) it's definitely too rich.

I would definitely focus on easy starting over getting perfect idle speeds though, a slightly fast idle is not harmful but hard starts are very harmful. My 924 idles a bit too fast (900 cold 1100 hot) but it literally fires on the first revolution with no throttle needed.