johntorg

Sorry about the image size. If you read carefully, I have already replaced the cap and all the plug wires. You can't swap the fuel injector leads because they don't reach. i guess I could make an extension to the leads so that I could, but I don't have any male connectors int the shop. Number 4 injector sprays under cranking and clicks the same as all the others when running, so I'm pretty sure its OK. Compression is there under cranking, but one of the valves may be sticking open when running. I am about to go to the shop and continue the investigation.

87 944 C

Sound like a spring

johntorg

That's what I suspect. I will pull the valve cover this morning to see.

peanut

you trying to tell me that the adjacent electrical connector from injector #3 won't reach #4 injector ?? just how tight is your harness ??

Like I said if its got sufficient fuel and a spark then it must be missing compression .
Thats about as basic as car mechanics gets mate ,its not rocket science.

Sorry I wasted my time trying to help. Looks like you already knew all the answers to this problem before you asked right . Another person who already knows the answer when you tell them !....

F18Rep

Good plan, I bet you find a layer of silt in the injector screen...btdt...Bruce

Funn944

bad injector or bad spark plug

johntorg

You are correct the wires on a stock 944 S2 Harness won't reach from 3 to 4 and vice versa, without cutting open the harness

johntorg

Problem Found It was a broken outer exhaust valve spring on the #4 cylinder (forward spring).

Thanks for all the help and suggestions.

333pg333

err...that's a bit over the top. Note that the cause was mechanical.

johntorg

Problem was found by checking each valve spring with my finger, when the valve was closed. You really can't see much on a 16V. Now to see if I can change the valve spring without pulling the head. I can use compressed air to hold the valve closed, but I don't have the proper valve spring compressor. Does anyone have experience doing this?

If that fails, I have a spare head that I can install, that is actually fresher than the one on the engine.

carlege

JoshB and i replaced one on a 968. It can be done.

Air pressure to hold the valve closed while you replace the spring. also having some one with vice grips holding the valve as insurance is good too

johntorg

What kind of spring compressor did you use? I think that if you put the piston at TDC, the valve can't fall too far.

KuHL 951

Porsche makes a special compressor tool (looks like a bottle capper) that bolts to the existing head but the rental ones that adjust for mounting centers are great. The rental tool can compress well past even a slightly dropped valve so it should be an easy fix if you can find one. Beats swapping a head for sure.

peanut

yes but because of your limited mechanical understanding you have completely missed the point.

I said that the reason #4 cylinder wasn't working was due to lack of compression in the cylinder ......I was right .

I cannot be expected to diagnose why there is a lack of compression in the cylinder from 2000 miles away can I ?

I gave a range of suggestions which didn't include broken springs but it doesn't take too much intelligence to check the valve clearance as I suggested and realise that a spring must be broken.

Any competent spanner monkey would recognise the symptoms of a burnt or broken exhaust valve by putting their hand over the exhaust tail pipe and feeling and hearing the compressive gases in the exhaust system.

Incidentally 333pg333 seeing as you're being so critical ,your contribution to diagnosing the OP's fault was what exactly ?

johntorg

Here is the culprit. I managed to create a "McGiver-like" spring compressor and install another valve spring pair. The replacement spring, from another S2 head has smaller windings, but is the same height. The inner spring appeared identical. The broken spring also has 2 red stripes on the upper couple of windings. Has anyone seen this before?