Need help!! please
 

Hello porsche fan,here my problem, i have a 1977 3.0 turbo, i found motor not run correct, i check exhaust emperature at the cylinder output and see, all cylinder about 230f at idle minus the cylinder 2 (driver side) about 70f.....so i know i have a problem!!!

I have 6 news bosch 002 injectors, first i change the spark plug..just in case..but no!

i test compression between a good one and this cylinder...egal.
i made leak down test 7%
i remove injector to test the patern.... patern ok
spark plug firing..

does the 7% leak down enough to do this? Someone have an idea? i,m not completly stupid (only on week end)...but this one made a headhach for me

(sorry for poor englisch)

thanks for your help

Your English is fine. 7% shouldn't cause a dead cylinder.

Sounds CIS to me since you confirmed spark and have new injectors. There's lots of experts here to help. Good luck. :)

Did you confirm spark on cylinder 2 or just change the spark plug? If not, make sure it isn't as simple as bad wires, distributor, etc before getting into more complicated things.

yes spark! i,m a mechanics for 33 years...but this trouble..i dont know???

Was it running properly before you installed the new injectors?

Since all of the basics seem to be OK, I would start with a basic tune-up especially timing.

I don't know much about cylinder head temps but two cylinders on either side of the middle cylinder are at 230F and the middle cylinder is at 70F. 70 F sounds extremely cold to me. Can you confirm that your CHT gage on cylinder 2 is working properly?

Rahl

I'm guessing an IR gun for header temp.
My guess would be an air leak on #2. You could try spraying some hydrocarbon stuff around #2 intake /plumbing and see if the engine picks up. Does the plug on #2 look different?
Regards
Alan

Yes, check the injector ring, intake gasket in that area

Not familiar with 002 injectors, is that a typo?

At 70*f the cylinder is not firing (assuming your temp testing is accurate).

When you say you checked the pattern on the injector, did you do that on the engine connected to the fuel system, or on a bench tester?

I would get a set of graduated baby bottles pull the injectors from the blocks, leaving them connected to the fuel lines, and stick all the injectors in them on the engine. Then with the ignition in "run" pull the safety switch connector off the back of the airflow sensor for 30 seconds. Make sure #2 is getting the same fuel as the others. There should not be any noticeable difference between cylinders.

You had reasonable compression and leakdown so it seems like a good chance the valves, seats, piston, rings are in reasonable shape. You could stick a borescope camera in the spark plug hole and have a look just to make sure. You could also pull the valve keepers and springs and make sure the valves move smoothly and aren't sticking. Sometimes a stuck exhaust valve will show this behavior, although on our motors lacking a pushrod or hydraulic lifter I doubt that's possible. Someone more knowledgeable can address that.

My bet is on spark though. How did you test spark? Just because you see a spark doesn't mean its at the right time, or strong enough.

An intake leak would have the cylinder running lean, raising the EGT and CHT, unless it was leaking enough to prevent a burnable charge in the cylinder. That would be a hole big enough to stick your finger in.

hello, thanks all for help. i check the injector connect to the fuel rail..since it is new, want to check if fuel distributor missing...but delivery ans patern ok For the spark, i check with a spark tester,also i put the spark plug on another motor..and ok. As for the temperature,i check directly at the output of the head. I,ll check with the boroscope...maybe i,ll see someting...but i,m very confused.

Crazy idea, but is it possible that the valves are adjusted too tightly on that cylinder?

When the engine is cold you get OK compression, when it gets hot you lose compression.

Another thought is that you have a broken rocker arm. I thought I had a dead cylinder once and it turned out to be exactly that.

I wondered about something like that too. But then you would get hot gas going out the exhaust?
Alan