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Misfire


SteveT

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Hi all, after filling up the '76 2.7 with 98 octane the other night I seem to have developed a misfire once I get to around 3,500 revs. It idles perfectly and runs fine at lower revs, seems to be a bit more prevalent when warmed up.

Is it fuel related? If not, where to start? Could be coincidental with filling the tank and not related?

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one of your injectors will probably be clogged. I've been told hitting them clears them up then change your filter

 

or maybe one of your plugs is fouled up

 

might be worth doing leads/plugs at the same time too

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Oh it could also be your fuel distributor, but I'd check the rest first

 

I'd totally forgotten I'd gone through all this myself lol, so now I've added it to my list of work I've done. The injectors are big brass b*stards - might be worth getting them cleaned ultrasonically.

 

lol but the time I had a misfire like that I changed my coil/leads/plugs and it cured it

 

I've got a coil you can test out if you want - what are your leads like?

 

also, the spark plug tool is the best thing ever.

 

feel free to bring it round sometime if you want, i'm in clayfield (with a flat tyre :()

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They are all what came with the car so history not known, will start with plugs, leads, points, condensor and see what happens.

As I'm just around the corner (ish) just holler if you need a manual,tools etc. plenty of advise on tap also not sure if its any good though :blink:

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Fixed it. Well temporarily at least. I cleaned the points and voila. I have a new set on order from James along with a couple of relays to keep,as spares. When the parcel arrives I will see how large my hands really are. Not much room to work and the points are towards the back of the distributor. The crowded bit not the uncrowded bit of course.

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Ok I'm over the romance of points ignition. Car was running fine, then started misfiring again. Cleaned the points. Wouldn't even start. Cleaned again, starts and runs perfectly. Next day has misfire at low revs and fine at higher revs.

 

James is currently researching breakerless ignition for me. I have my fingers crossed that I can do something at a reasonable price and be free of ignition points for ever.

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Ok I'm over the romance of points ignition. Car was running fine, then started misfiring again. Cleaned the points. Wouldn't even start. Cleaned again, starts and runs perfectly. Next day has misfire at low revs and fine at higher revs.

James is currently researching breakerless ignition for me. I have my fingers crossed that I can do something at a reasonable price and be free of ignition points for ever.

Totally agree, had motorbike years ago with 2 sets of points! and the same problems. Bought bolt on kit to replace them for around $200, which was a lot of dosh at the time but it was worth every cent.

I would have a look at Russ's suggestion as I'm sure he would have researched it extensively, I don't google stuff on Porsches any more I just ask Russ:)

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I agree with Russ, go with Petronix.

They pretty much are the aftermarket yardstick.

I'm sure there are other brands out there that are made from billet something or other especially for Porshes with the appropriate price tag but why quack in to their little game.

I have no need on my 3.2 but I have used on various others and it is set and forget stuff.

Still have Petronix on my old Thunderbird though and it is the beez kneez. 

Easy to fit too.

When you open the packet for the first time though you wounder why they  are so expensive, there is nothing to the kit.

You can't make them at home though.

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Remember folks, 9 out of 10 fuel problems causing misfires are due to the ignition system :)

 

Not sure on best options for the 911 but I'd have thought the SC 3.0 distributor with a bosch igniter (valiant/sigma/magna) would be an easy and cost effective swap.

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James suggested Pertronix. All up and with a new hi voltage coil and freight it's around $350. But I still have an old distributor with old shaft and bushes. I did get on to a local guy with great references that will build a full electronic, refurbished, dissy for $800 - $900 using easy to get VW electronic internals and new bushes etc.

 

The current plan is that now the old fart has a new set of points (and battery, the old one died yesterday) is to just drive and enjoy for a while.

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