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FASTdan · Joined: 30 Jan 2006 Posts: 81

Hi, its been a while since I've been on here as I sold my last 924 a couple of years back.

However recently I've been hankering after a turbo and have come across one locally that may be a good buy. Its been stood for a couple of years and has 134k on the clock.

From cold it will start but needs a bit of encouragement from the accelerator to maintain idle for about 30 secs. After that there is a definite misfire at idle and through the revs (including some popping/backfire). The response is slow due to the misfire and it feels hesitant to rev. Once warmed up this misfire is nearly gone but not quite, still definitely evident. Unfortunately the car has no brake callipers so is not driveable to check how it pulls.

No smoke from the exhaust, heater gets warm, oil seems clean, oil pressure once hot is 1 bar (is that ok? I recall it perhaps should be more?). Bit rattly on the top end - again I cant remember if they are adjustable valve clearances or hydraulic?

Just after some ideas on what it could be? cold start valve? though the mis is still slightly evident when warm. Im not familiar with the engine management on these - whats a worst case?

Its a series 1 1978 turbo.
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1980 924LUX

fiat22turbo · Joined: 18 Jan 2006 Posts: 4040 Location: Portland, OR

Well, first:

How's the timing belt? If it snaps, you're borked.

Second:

Vacuum leaks, check for them and correct them. (Note: there are some noted for leaking that run behind the timing belt)

Third:

Engine is essentially the same as your old 924. Same cam and lifters, different head and pistons.

Fourth:

Buy/borrow a proper CIS pressure test set.

Fifth:

Replace the plugs, wires, cap and rotor, then go through the electrical connectors to make sure you've got good, clean connections.

If the problem still isn't cleared up, then you have a stable spot to work from as it could be the WUR or some component in the CIS fuel system.

Good luck!
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Stefan
1979 924 Carrera GTS (clone-ish)
1988 944 Turbo S (Silver Rose)

SlayerSST · Joined: 21 Sep 2010 Posts: 212

emoore924 · Joined: 13 Apr 2004 Posts: 2822

there is no 1978 turbo.

FASTdan · Joined: 30 Jan 2006 Posts: 81

924RACR · Posted: Fri May 11, 2012 9:53 pm Post subject:

Likely the warm-up regulator not working well... though perhaps not completely dead, and may be just in need of some adjustment.

Compression and leakdown tests would help isolate any cylinder problems...
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Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

knobby · Joined: 23 May 2011 Posts: 43 Location: Cincinnati,Ohio

It sounds like a problem I had with my 81 931 which I eventually found to be that cylinder 3 was getting flooded out by its fuel distributor supply segment.
It was pouring fuel in even on idle(a lot)and this was also accompanied by a very rich raw fuel smell from the exhaust and of course the obvious misfire which amazingly enough went away on WOT.
I confirmed it by removing the injectors and jumpering the fuel relay whilst measuring the fuel delivery to each by placing them all in bottles.
Fortunately for me I had a spare FD which came with the car which I swapped out and it fixed the problem.
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81 RED 931 S2(daily driver),81 WHITE 931 S2(not currently drivable).
Cincinnati,Ohio