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Ozzie · Posted: Thu Aug 01, 2013 11:19 am Post subject: For the unwary

I have been plagued with bad running ever since I replaced the head gasket in April.
I replaced most ignition bits, double checked valve and ign timing, adjusted the A/F mix using a gas tester, checked for ign leaks and basically went over all the obvious stuff. Check fuel flow etc.

Had some improvement after replacing the coil and dissy cap.
Still had a miss at idle, bad misfire under medium and hard acceleration and stalling.

While checking the TIU as part of the Haynes manual checks, for some reason I checked the earth from the TIU to the battery. High resistance. This should be zero.

Cleaned up where the TIU mounts on the body and now purrs like a kitten.

SORTED!!
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Porsche 924 1984 (UK import) NA
Its AUTO and its BLACK
Montego Black on black/red
Engineer of Electro/Mechanical Systems Maintenance

Rasta Monsta · Joined: 12 Jul 2006 Posts: 11733 Location: PacNW

OK, IB. WTF is TIU?
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Toofah King Bad

WeiBe (1987 924S 2.5t) - 931 S3

ideola · Joined: 01 Oct 2004 Posts: 15550 Location: Spring Lake MI

Transistorized Ignition Unit.
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erstwhile owner of just about every 924 variant ever made

DOCO · Posted: Thu Aug 01, 2013 10:54 pm Post subject:

Grounds grounds grounds so important. They are even more important now with all computerised fuel injection and computerised transmissions.This is one of the biggest issues with diagnostics in the late cars. Everyone forgets the grounds!!!
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Doco "where am i going and why am i in this handbasket"author unknown
79 924 N/A "Webster"
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[+]___[+]
\0 924 0/
[__]..[__]
"WEBB STR"

Ozzie · Posted: Fri Aug 02, 2013 7:15 am Post subject:

By habit I check my multimeter every time I turn it on.

I had one lead on the -ve and touched what should have been a good ground. (body of TIU). When I got nothing I had a WTF followed by an AHA! moment.
_________________
Porsche 924 1984 (UK import) NA
Its AUTO and its BLACK
Montego Black on black/red
Engineer of Electro/Mechanical Systems Maintenance

Ozzie · Posted: Thu Aug 15, 2013 8:16 pm Post subject:

Didn't last long.
Bad running returned.
Think I found the culprit this time. The new rotor button has zero resistance.
the book of lies says it should be about 5k so tested the old one and refitted it. at 4.8k it seemed good enough.
runs a lot better so now looking for another new rotor.
will test run again tomorrow.
_________________
Porsche 924 1984 (UK import) NA
Its AUTO and its BLACK
Montego Black on black/red
Engineer of Electro/Mechanical Systems Maintenance

Joes924Racer · Posted: Fri Aug 16, 2013 12:25 am Post subject:

No pics
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1979 porsche 924 Na
1980 porsche Turbo 931GT Replica
Have u ever driven a turbo.

Ozzie · Posted: Sat Aug 17, 2013 7:55 am Post subject:

Two days now, no misfires, runs and pulls well.

do you want pics of a rotor?
_________________
Porsche 924 1984 (UK import) NA
Its AUTO and its BLACK
Montego Black on black/red
Engineer of Electro/Mechanical Systems Maintenance

sbarc · Posted: Sun Aug 18, 2013 5:22 am Post subject:

I would love to see a photo showing the location of the "Transistorized Ignition Unit"....so I can check my own car.

Anyone have any idea where this unit is?
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1981 931 (Canadian car)
1981 931 (US car)
1990 928GT (ROW car)
1991 Toyota MR2
1989 Toyota MR2 Super Charged
1985 Toyota Supra
1973 Triumph GT6
1971 Opel GT

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

Behind the driver's headlight on the front of the inner fender. Small silver box about the size of a pack of cigarettes.
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Stefan
1979 924 Carrera GTS (clone-ish)
1988 944 Turbo S (Silver Rose)

Paul · Posted: Sun Aug 18, 2013 10:58 am Post subject:

Yep check those grounds, this is a 924S main engine ground point:

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White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.