924Board.org

[max924]

Got a '77 924 NA and I am having trouble getting it to run right. When I start it cold it starts and idles but if I give it gas it wants to die out as if it is suddenly to lean (and you can hear the sensor plate bouncing around maybe even a bit if backfire?). It also misfires occassionally. It is driveable after 10 mintutes of idling but still misses with poor accelleration and surging while cruising along. The car does progressively drive better after an hour or two of constant driving but never perfect, it will fully rev out but between 4grand and 5 it is more hesitant than the rest. Things I have done: I have done the entire ignistion system check(as per Haynes) and even exchanged the dist., coil, and ignition unit with others with no difference. I set timing but if I go off the flywheel it is way off (no real markings may be aftermarket flywheel) so I can only set it by going with the best position it runs at. I have two new filters on order, the one before and after the pump, and I installed a new Pierburg pump which made no difference ( don't worry the pump came with another car). I can not seem to find any definitive air/vacuum leaks although the rubber ducting is showing its age and I have attempted to repair some cracks around the sealing edges. When I do a fuel delivery test I get 650 cc (not good) when lifting the sensor plate and 750cc (good) when running the starter for 30sec. It performed like this before and after I did a total rebuild of the head. The way it was missing all the time I thought fior sure ignition but all components are good. I don't see the filters being the complete problem as they are not that old. A long while ago I tested the injectors and they were all OK along with cold valve. The sensor plate is properly centered and moves smoothly. It is very frustratingjavascript:emoticon('')
javascript:emoticon(''), I am considering megasquirt and EDIS. I have also determined that it is not the AAR(auxiliary air regulator) or the cold start valve becuase unplugging the cold valve makes no diff and removing the AAR makes no diff.
Any ideas or previous experiences are GREATLY APPRECIATED!

certainly my longest post yetjavascript:emoticon('')
javascript:emoticon('')

MAX

[Paul]

Time to borrow or buy a CIS tester to verify the system is working correctly.
_________________
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.

[Chrenan]

How old is the fuel pump?

When you said you "exchanged the dist., coil, and ignition unit with others with no difference", were the "others" used as well or new?
_________________
1987 951 - M193 Version for Japan

[Lizard]

have a shop check the air fuel mix and try to have them tune it.
_________________
3 928s,

[Stampedetrail]

Seeing how you did a total head rebuild it should be some minor point you're overlooking. Or major, I dont know, but in any case you could check your spark plugs. Are they super black? If so your mixture is probably too rich, if they're blue & burnt looking its probably too lean, although you dont want to touch it until you're sure you checked & plugged all the vacuum leaks. There's also a possiblity that some componant of the fuel delivery system has failed-- there are quite a lot of failure points in the system. The accumulator usually goes out after 30 years. Also, what about fuel filters? If one is clogged the whole system gets out of whack.
_________________
1977.5 924 "Martini" head / New Old Stock rebuild
1985.5 944 Why? Because I can.

[max924]

Fuel pump is brand new never used. All ignition components I used were either new ones or worked on other cars fine.
I rebuilt the head because it was cracked, and the sparkplugs do look fairly black. Will be replacing fuel filters soon.
Isn't there a way of adjusting air fuel mixture with shims in the fuel distributor?

[Ozzie]

This may be a silly question but what firing order do you have the leads in?
_________________
Porsche 924 1984 (UK import) NA
Its AUTO and its BLACK
Montego Black on black/red
Engineer of Electro/Mechanical Systems Maintenance

[max924]

not at the car right now but I believe it was 1342? can't remember

[924RACR]

You adjust the mixture with a long-handled (T-handle) 3mm allen wrench between the fuel distributor head and the air intake boot. And yes, it definitely sounds like your mixture is out. At worst case, it could be a warm-up regulator, but you have to try the mixture first.

Where in Ontario do you live?
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

[max924]

Maybe tonight I'll fool with the mixture. I am under the understanding that a fuel filter for a '82 jetta will work on my car, is this true ($30 compared to $70).

I live between Port Elgin and Kincardine on Lake Huron, an hour north of grand Bend

[max924]

Awesome!! I adjusted the mixture and it runs pretty damn good. I never realized this car could be peppy. I adjusted the timing also by going 10 degrees off the mark on the crank pulley which worked fine. Really appreciate the help, this forum is great! When I got it going good and took it for a test drive had a huge grin on my face, greatest feeling ever, well almost! Once again thanks, I should have known it would have been this simple, I even have the damn BOSCH book for tuning these things and never bothered to look there. at least I didn't spend big cash trying to figure it out.

Thanks,

Max

[Porscheaddiction]

Max just curious where in Ont are you ?
Chris.
_________________
1981 924 NA (Restoring mode)
1984 928S (Enjoying the driving season)

[924-76]

Max924 wrote

I adjusted the timing also by going 10 degrees off the mark on the crank pulley which worked fine.

I'm not a pro in mecanic, what's that mean? How can I do it?