More test results, getting scared now!

[lendaddy]

Thanks for the offer Tom. After I do the leak down and see no problems there I will try the propane torch.

[Superman]

Lendaddy, I'm still suggesting you relax. In another thread, we're discussing rev limiters and maximum permisible engine speed. I exercise my rev limiter frequently. If a piston files out the side of the engine leaving a gaping hole where it and a cylinder head used to be, I'll probably go visit JW (he's got piles of used engine parts). I figure hey, it's a machine. Made of parts. Used parts. Replaceable parts. I think it's fun looking at bent parts. I think it's fun pooping around my garage repairing Porsche stuff. And almost anything can be done fairly economically. We're here when you need us, lendaddy. You don't have a cracked engine case. Relax.

[5axis]

It appears you are working through the mechanical possibilities. Have you considered the fuel quality? Every summer one of the boats on my lake goes through some "water in the gas" problem and runs like S*#@. until the tank is drained and fuel replaced.
david 89 turbo cab

[WERK I]

Originally posted by lendaddy
With the idle off slightly I get just less than my 7 degrees required retard at 950 rpms but I figure that could be a funtion of the poor running. I would say its's at 4-5 degrees. I let it warm up more the other day and it idled better but still missed under load. (the timing got closer to 7 degrees retard when warm as well). I would like to believe it is a vacuum leak but I cannot find anything!

lendaddy,
You're setting your ignition at 7 degrees ATDC(retarded) @950RPM? I don't see that spec anywhere in the Porsche tech manual. Looking at the manual, and using the Euro specs, I see;
idle speed: 1000 +or- 50 RPM
0 degrees +or- 2 degrees(range 2degrees ATDC - 2degrees BTDC)
this is with the vacuum hose connected to dizzy.

At 4000 RPM(with the vacuum hose disconnected) you should have 26 degrees +or-4 tolerance BTDC

[lendaddy]

The US version is a little different

[pbs911]

I think it is something simple. When you say the spark plugs are new, how new? Sounds like the exact thing that happened to my 3.6. I couldn't find a thing wrong. I had an extra set of plugs lying around and they solved the problem. You said the wires are conducting a spark, but is the spark making it into the cylinder? I don't know if it is proper, but maybe try pulling a wire at a time with the motor running. If there is a change in dle at least you know that cylinder is probably OK. Just use a wire puller so you don't get shocked.

[Superman]

I have a feeling Paul is right. Hard for me to imagine this is a mechanical problem. I think you're going to find it is something embarrasingly simple.

[lendaddy]

As you might imagine I will gladly play the fool in this broadway show for a simple fix!

[Alan Cottrill]

have you checked your control pressure?

when I had a problem with my WUR I checked my injectors the same way you did...great flow. but with low control pressure it was too easy for the sensor plate to lift and when I got up to about 3k rpms the sensor plate was opening too far and causing the engine to go too rich.

I dissassembled my WUR cleaned the screen up and while I had it apart made it adjustable.

when I put it back together I set the cold control pressure and monitored the pressure as it warmed up and It functioned within accepatble parameters.

long story short...low control pressure can cause the engine to stumble at about 3k rpm and down right cut out at 4k.

[RoninLB]

[911pcars]

I don't think a burnt valve will cause a stumble; bad idle maybe.

A compression test should be the first diag. item to perform, then a leak down test. It's easier and faster and should rule out any mechanical problems. Perform a leak down test if any cylinder(s) are down on pressure.

Have you tested your plug wires (and secondary circuit from dist. to plugs) with an ohmmeter? Brand new things don't always work 100% of the time.

Fuel pump pressure seems okay. How about fuel pump volume (not injector volume)?

Try opening up the plug gap to .040"-.045". You fouled last year with the stock system, yes? You don't have stock system now, yes? Try it and see if it makes a difference. Also conduct a cylinder balance test as suggested.

Sherwood Lee
http://members.rennlist.org/911pcars

[Vintage911Racer]

Len, are you still running points? It is possible that your dizzy needs to be rebuilt. Mine would dosomething similar. Would Idle pretty good but when I got on it it would start to miss. The Cause: distributo shaft bushing had worn out and I had some free play in the shaft. So at high RPMs I would get movement in the shaft thus throwing the timing and points gap off almost acting like a rev limiter. Had the Unit rebuilt and now have no problems. Just my 2 cents. Good luck.

[rfng]

Do you get full boost?