Two Pistons Good, Two Pistons Bad

[Porsche37]

I related a post before, forgive me if you read before, but I think it was deleted...

So I have a 944/2 N/A, 1985.5... Recently she just started running bad, out of the blue. Recent repair was fuel pump replacement, but I see no connection. Yes, fuel pressure is good. Some remedies I made was flush the fuel tank completely... fuel did smell bad btw... I reside in Belgium and the new biofuel mix has a limited shelf life. New plugs, distr cap, rotor and wires. Injectors are very new, vacuum lines all replaced and checked. Compression check is good, nr. 4 is a little low at 163 all the rest are above 168. Did this today.
Now for some reason nr. 1 and 3 cylinders are firing and nr. 2 and 4 are not.
I am almost positive I have fuel in each cylinder, but I will verify again. Does anyone know why only two pistons would be firing and two not? Two mechanics and one garage helper have no idea... Any thoughts on this???

[v2rocket_aka944]

are you sure the distributor wires are plugged in correctly?

4-1
2-3

[ckelly78z]

Make sure you gapped the plugs correctly, and that the firing order is correct, after that, I could be a dist cap that is bad. Beyond that, it sounds like something serious.

[Lapkritis]

Originally Posted by v2rocket_aka944

are you sure the distributor wires are plugged in correctly?

4-1
2-3

x2, sounds like firing order.

[Porsche37]

Thanks for all those who jumped in. I pulled the injectors and found some of the worst gas I have ever seen. Flushed the fuel into a clothe to keep it off the engine. Real nice bronze rusty color came out... Just some of the nastiest looking stuff I have seen...

[ckelly78z]

Has the car sat for a few months to allow the fuel to go bad ? Maybe this new Belgium biofuel mix goes bad quicker than you thought.

[TibetanT]

Porsche37:

How long have you been using the "new biofuel" in this car?

I might suggest draining the gas tank completely and putting in high octane gasoline to see if the car runs. This will give you an idea whether or not all fuel related and ignition related components are functioning properly. Flushing all remaining "bad" fuel out of the system.

Since you live in Europe, would also like to suggest getting a hold of Porsche factory to find out if our older 944 cars are compatible with this newer biofuels and what they might offer in regard to the newer fuel.

Not an expert, but that is what I would do before adding/switching to the bio stuff.

Hope this helps.

[Porsche37]

Switched to the older injectors and the response was slightly better. I plan on cleaning the injectors that were dirty from the bad fuel.
As for the biofuel the problem is this type of fuel is common at the service/gas stations here. I am not the first to experience this problem a few friends I have that restore vehicles started noticing the shelf life of biofuel was much shorter than expected. A very common problem now. I am just going to have to run gas additive in the tank and clear up what has gone wrong.

[Nolan197]

It seems you've already found the root of the problem but another suggestion would be to make sure the distributor cap is on securely. PO for my car said it was fireing on 2 cylinders problem was the bottom spring latch for the cap had popped off. Tightened it up and she ran like a champ.