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foxtg557 · Joined: 05 Aug 2007 Posts: 99 Location: Hamilton On

Hi, I have a 1977 924 and it has some engine issue's.

when I first get it going I can rev the engine, she sounds nice... Within about 30 seconds or so of her running I start loosing a lot of engine power and can no longer rev it high. I'm not sure what the issues are but when I got the car there were vac lines not in the right spots or plugs covering up where vac lines should be... I have put lines back where I believe they should be but am not 100% sure if I got them right I was wondering if a vac issue could be what is causing my engine symptom.

Does anyone have a good vac diagram for a 77 924 ?
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77 924, It Drives !

Smoothie · Posted: Tue Aug 14, 2007 1:37 pm Post subject:

Could be junk in the fuel tank, or a clogged or backwards fuel filter, clogged exhaust, control pressure problem compliments of a bad WUR, possibly even a bad coil..
The Haynes has your vacuum line routing diagram. Looked there?
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"..it's made in Germany. You know the Germans always make good stuff."

'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

dgKnecht · Joined: 17 Nov 2002 Posts: 42 Location: Palatka, FL

iirc there is an air valve that is closed on cold start, and it opens
shortly after engine is warmed up, maybe a hint to something air/fuel
but sort out the vaccuum stuff first, my car was like that when i got it,
many lines disconnected, etc.
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78 924

--all of us have been through some bad times.....i once had a job where i had to drive a Chevette

924guy · Posted: Tue Aug 14, 2007 11:05 pm Post subject:

i had a similar issue in my 78 , a long long tine ago, drove me nuts... i still don't know what the true issue was, i just kept placing things until it stopped, but i always suspected it was electrical related.
after you get your vac hoses sorted, the next thing i would do is clean all electrical connections and grounds, carefully disconnect, clean, and coat them with dielectric gel before plugging each one back in, including those at/behind the fuse box (careful, don't mix them up..) its something that probably needs doing anyhow, and it costs nothing but some time and elbow grease. at the very least check the fuel pump leads for corrosion behind the fuel pump relay.
another place to look is at your positive battery cable, i had one that was corroded and built resistance as it heated up, and the car would actually cut out, felt like a fuel issue, wasn't.. those cables are NLA so you'll have to build one yourself to replace it, worth the effort though..

good luck...
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78 924
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Benino · Posted: Wed Aug 15, 2007 1:32 am Post subject:

My guess is warm up regulator (control pressure regulator). It if were a dirty filter or tank I think the problem would be there the instant you started the car. The warm up regulator changes control pressure as the car warms up, so if it is dirty or just not working correctly it could cause the AFR to be too rich or too lean as the engine warms up. Pick one up at the junk yard or open yours up and clean it. My car had an issue like yours (not as exaggerated) and it cleared up after I took the WUR apart and cleaned it up.

It's not the auxiliary air valve. All that does is bypass the throttle by opening when the engine is cold and closing as it's element heats up. It just mimics having the throttle open a little bit when the engine is cold.
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1980 Porsche 924 N/A USA
1980 Porsche 924 turbo USA
1987 Porsche 944S USA

Smoothie · Posted: Wed Aug 15, 2007 4:25 am Post subject:

Oh yeh - I knew I was missing something - couldn't remember it before.. Some with these symptoms have said that their fuel pump relay was the culprit. It would work at first, then the relay would quickly overheat, causing running problems or shutdown. Easy check - jumper 30-87 on the fuse-relay board with the fp relay removed. -But only for testing (otherwise the fuel pump/s will continue to run even with the ignition shut off if the jumper wire is left in place)(+ the circuit will be un-fused (unless you make a jumper with an in-line fuse)).
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"..it's made in Germany. You know the Germans always make good stuff."

'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

foxtg557 · Joined: 05 Aug 2007 Posts: 99 Location: Hamilton On

Thanks guys for the responses... I guess I should describe a bit more... I don't feel it's something to do with it warming up because after the engine dies and things are warm I can fire the engine right back up again, starts fine but goes through the same pattern, I can get one good rev out of it and then it sputters / idles and all power on the engine is gone... But I can always ( after the engine dies ) I can always fire it right back up to a nice idle...
Also the fuel pump never quits I hear it come on while the car is running... she works but she is a loud pump... when I have 300 bucks to replace it i probably will

There are several large vac lines that I don't know where they go, tomorrow in the light I plan on taking some pictures to post but there is one vac right on the cold start valve on the top of the intake that im not sure where it goes, the line coming from the charcoal canister I don't know where that goes aswell there is a line if you look right straight down to the left of the cold start there is another part ( not sure what it is ) but that has a large vac line on it which I don't know where it goes...
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77 924, It Drives !

foxtg557 · Joined: 05 Aug 2007 Posts: 99 Location: Hamilton On

Okay So I am having issue's figuring out what vac lines go where and I was hoping some pictures would help the situation... There's I believe 4 large vac lines that don't go anywhere at the moment.

1) Line coming from the charcoal canister at the front right of the car...
2) Line coming from the top of the cold start
3) This seems home made but was there when I got the car... A Line coming from the intake boot going to no where :S...
4) this I'm not sure what this line is coming off of, it seems to be a bit bigger in diameter than the line from the cold start ( number 2 ). It is located in between the egr valve and the cold start just a little bit lower...

Side view of number 2 - cold start vac line.

Another view of number three - the homemade looking piece coming from the intake boot. Also you can see number 4 in this picture, it is the piece with black electrical tape on it.

This is number 4, im not sure what it is but it seems to be sucking air and I'm not sure where that line is suppose to go.

Lastly there is another hole that blows air, it seems to be above the oil pan or something ... It blows air, when i plug it - run the engine and once i unplug it oil will shoot out, plugging it seems to be pressurizing it, im not sure if there's suppose to be a line on this hole or not ?

in the dead center of this image in the back you can see the little metal hole.... The next image is a close up of it.

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77 924, It Drives !

Mike924 · Joined: 12 Aug 2004 Posts: 2601 Location: IoW UK

You're missing the AAV (Auxiliary Air Valve), Foxy. It should go between line 2 and line 3 in you photo.

Line 1 :I suspect you could leave the charcoal canister disconnected (or throw it away) unless your emission laws require one.

The mystery hole that blows air/oil out is the crankcase breather. It should have a pipe going either to the air box on early cars, or a branch on the plastic intake pipe (between the two big rubber ones) on later cars (I can't remember when they changed over from one to the other). It kind of looks from the photo that the stub pipe on the breather has been sawn off...?

I think line 4 in your photo could be the breather pipe which should connect to the 'hole'. Trace to see where the other end of it goes. If it's either of the two places mentioned above, that's our baby!

I think it's safe to say your car's last owner was a butcher!

P.S. Sorry for the number of edits

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1985 Porsche 924 'Lux', Kalahari Beige (my ex)
1993 Porsche 968 Coupe, Midnight Blue, 6 spd

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foxtg557 · Joined: 05 Aug 2007 Posts: 99 Location: Hamilton On

Thanks for the reply Mike, and yeah he was a butcher when it came to the electrical, but as for those lines hacked and random... they really weren't there when I got the car, instead they were plugged with cork from wine bottles :S It runs a little better without them and with some guess work on where they might run to but I've had different lines made and cut and taken off etc etc and some that you see in the pics are just there acting as a plug with tape on them. I'll see if I can figure these things out.

I don't think my intake has the AAV on it, I'm assuming that might be of use to me ^^ heh. I bought a newish intake i believe it's from a 79, I bought it havn't put it on yet but I know it has an AAV on it, i'll test it tonight and see if that helps my case.

And it might make sense that the mystery hole goes to number 4

I'll see if i can rig something up to try that...

Thanks much !
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77 924, It Drives !

Mike924 · Joined: 12 Aug 2004 Posts: 2601 Location: IoW UK

The AAV is a separate unit bolted to the inlet manifold, not part of the intake boot. It looks like you'll need to buy/beg/borrow/steal one. Here's a picture of one , so you know what you're looking for:

Also check to see where line 4 goes before connectiong it to the breather stub.
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1985 Porsche 924 'Lux', Kalahari Beige (my ex)
1993 Porsche 968 Coupe, Midnight Blue, 6 spd

'There is no substitute for a little grease under your fingernails.' - Chrenan, 924board.org