Stumbles Intermittently

[Jhalsey]

Could you post a picture of your custom spark plug tool, words are not doing it for me. I used the Porsche spark plug tool. When you say “they don’t look flash”, not sure what you mean. Also, I wouldn’t describe my problem as a “miss”, its more of a hesitation and reluctance to take throttle, comes and goes. Otherwise it pulls hard, no missing. I will ask Permatune about plug gap when I talk to them hopefully today. The gap on this plug measured .023”.

[Alan L]

The length is important. Shorter and it will slip down any plug hole easy. But then it is inside the head and you can't get it out (easily). Too long and it is easy to extract but won't slip down the hardest holes.
This thing drops in to #1 cylinder easy, which is probably the trickiest. It is a magnetic plug socket so it pulls the plug with it.
Works real well with a 3/8 drive small socket wrench.
Alan

[Jhalsey]

Thank you for the pic, I can see how this would be helpful.

I think I found the root cause of my symptom, or at least one of them, time will tell. I applied vacuum to the distributor ports. I expected to see the rotor move, but there was zero movement. I can move the reluctor (not sure of the name) wheel by hand but not with vacuum. The advance port holds vacuum but the retard port slowly leaks down. There is at least 3/16’ axial play which probably explains the somewhat raggedy appearance of the contacts inside the cap.

So it would seem the distributor needs work. I will remove the rest of the plugs, find TDC on cyl 1, note where the rotor is pointing and remove the distributor. Is this the type of job I can do myself? I have a friend that has a distributor machine.

I think I saw a rebuild kit from Parts Klassik for over $200 but including a cap and rotor. The side play is near zero so I don’t think the bushings need replacement. Can anyone recommend a shop to rebuild my distributor in the event I decide to go that route? I just don’t want to wait for weeks to have it done.

I spoke to Permatune (Lonnie) and reviewed my measurements of the coil and CDI unit. He didn’t think there was anything to indicate the coil or ignition unit had failed but offered to put them on his test rig to verify. I may do that but at this point I am inclined to forge ahead and get the car back together once the distributor has been addressed. It’s been apart on my lift for over a month as I’ve been digging deeper and deeper with all your help. I have a new Permatune coil and a new Yellow relay. Rotor and cap on the way.

The blue vacuum hose is connected to an electronic valve located about 18” above and to the left. There are two valves there side by side. The one on the right does not hold vacuum when unpowered, not sure if it should. I think I read something about the function of this valve being at start up only but could use a tutorial on its function and how to test it, thanks.

[krasuskyp]

for plug removal, if you haven't yet - remove rear wheels and do a 'partial drop' of the motor from the rear mounts, gives you substantially greater plug removal access. Driver's side still a bit of a hooor regardless fersuredly.

I once had the tiny plug 'tip' fall off (on the hardest to get #1 butofcourse) and wedge itself between the head and the plug's hex, unbeknownst to me - THAT was a "good time"... lol - just an fyi/beware 8)

I'm no rocket scientist but I don't think 3/16" dizzy shaft axial play is a concern, radial is more the issue. Your rotor was def cooked, and where there's smoke there's fire - I'd swap the cap too if you're not (tho I assume you can 'read' yours well enough to tell).

The rear cap clip def sucks colossal baulz to do / undo - worse than pubescent us fumbling with a bra strap certainly. If you've got ginormous meathooks for mits, consider enlisting a household resident midget with smaller hands to assist. Me, I went crankfire and rid'd alllll of alllll of allll that

That one plug you posted looks super sooty. Def pull the rest & compare / clean / determine why.

You're on the right track and your car will be grateful for it and you'll appreciate the toils of your efforts - don't rush getting it off the lift, do what it takes / needs. You got this



ps. it's conventional (required / demanded?) here to post pics of one's car when seeking advice Chop chop...

[Jhalsey]

Here’s a couple. Will post more later. 1989 930 w sport seats, white Fuchs from factory. 50k miles, 37k when i got it in 2015.

[krasuskyp]

WOW! Superazz COOL... and great ownership / usage. Way to go.

Where in NY are you? We often gather together a buncha area turbonutz for driving outings, etc. if you're ever interested...

[Alan L]

Thats a cool looking car.
You are on the right track.
There is a vac line to the dizzy that only works when the car has warmed a bit. It keeps the timing retarded early on - so that may be the one you are talking about. It is plumbed thru a thermo switch.
By all means check the dizzy - your vac adv/retard may not be working - they do fail. When you get the dizzy out you could check it if you have a Mighty vac - that will give you pressure and vac. There is an arm that runs from the vac can to the mechanism below. You may be able to see it by pulling the rotor and the plate that sits below it. It should move with Vac/pressure.
As for pulling the dizzy, yes - helpful to get to Z1 (#1 firing). There is a notch on the body of the dizzy for the rotor to line up on (so you dont confuse with #4). It should be pointing at about 2 o'clock. It may be hidden by the plastic cover plate on the dizzy base. When you have Z1, pull the dizzy - just that 13mm nut at the adjuster base.
Hint - I use white marker pen and mark where the timing is set now - on that adjuster base. If the timing was right, saves a job later.
The dizzy drive gear is helical. So the dizzy rotates when you pull it out. So you need to compensate for that when you put it back. Trial and error will tell you when you have counter- rotated just enough to engage the right tooth for the dizzy. It will land back at your 2 O'clock.
Alan
PS - if you make a plug tool like mine, you can get all the plugs with everything intact, incl the intercooler. I could give you the length of my unit but that will likely mislead. Unless you have exactly the same plug socket, the internals will be different. But you want the head of the bolt to sit near flush with the cyl head - just enough poking out so you can grab it with your fingers.

[Jhalsey]

I'm in Orient, the very eastern end of the north fork of Long Island. Always interested in hooking up with like minded car people.

[Jhalsey]

Well, got all three plugs out on the passenger side. They all looked sooty but cleaned up easily. I’m not optimistic about the drivers side. I cannot even see them from above, even after removing the large rubber elbow going into the intake manifold. This car has all the original smog equipment still intact.

So I’m moving on to pulling the distributor. I don’t see a way to turn over the engine by hand, tried the alternator bolt, pulley just slips so I will just keep trying the starter and hope I get lucky.

Here is a picture of the valve attached to the blue (retard) hose. If anyone can tell me how to test it I would be grateful. It does not hold vacuum when unpowered, haven’t tried w 12v there. As you can see, there are two similar valves adjacent to one another.

[Gunzel]

20 or 30 years ago I had problems with 2 911 cars, not turbos. I had a high speed miss that I could not eliminate. I finally noticed the tack seemed to be acting a little strangely.
I unplugged the Purple / Black wire from the dizzy to the Tack and the miss went away. If you look at the parts book for the 1973/75 RSR you will find a optional Mech Tack. Apparently the factory knew the Tacks could effect the way the engine ran. Almost no one I have talked to ever heard of this possibility.

Mike Curnow

[Jhalsey]

My symptom is not a miss at high speed or any speed, its a stumble or hesitation that persists and prevents much throttle input until about 4000 rpm. You have to nurse it along. Not consistently, comes and goes. Once it clears, pulls hard with no missing evident. I’m thinking it may be that the vacuum advance is not working. The vacuum advance port holds vacuum but fails to move the rotor. I will look at this more closely when the distributor is out. Also the green wire that carries the trigger signal from the distributor to the CDI unit. My tach is behaving normally.

[Alan L]

You won't get lucky trying to land on Z1 by luck with the starter. Not gonna happen.
You can use the pulley tool, or I use a socket on the pulley nut. It helps if you have the plugs out. You got 3 so thats a start. But you put a bit of pressure on the slack side of the fan belt at the same time you turn the pulley.
Alan
PS - you are rotating clockwise.

[Bucketlist]

Originally Posted by Jhalsey

My symptom is not a miss at high speed or any speed, its a stumble or hesitation that persists and prevents much throttle input until about 4000 rpm. You have to nurse it along. Not consistently, comes and goes. Once it clears, pulls hard with no missing evident.

Been keeping an eye on your thread and you may be on the right track butt.....from day one your symptoms told me that you are lean when under load. Do you have a wide-band air fuel gauge you can see under load or better yet a fuel pressure gauge in the cabin showing control pressure under load?
If your distributor repairs don't fix this problem I would look for ways to check control pressure under load and if you haven't looked for air leaks at the turbo up pipe and all the way to the throttle body you may need to check this with a smoke test.
Good Luck!

[908/930]

Regarding your distributor, 3/16 "axial movement" sounds excessive, don't think that is your problem though. One of those pots is intended to see pressure to remove dist advance, so applying Vac will likely have no effect. Search this forum for 'Ultimate 930 distributor, advance, retard, timing. On the last page 29 there is a cutaway pic for the pot. Does your rotor rotate freely by hand counterclockwise? Should feel some spring tension that is your mechanical advance.

Those Vac valves are just solenoid air valves, so 12v power on will allow air to flow through power off will close one port but leave one port open to atmosphere. The lower one in the pic the dist pot still is allowed to vent through the valve, but closes the port to the throttle body.

[908/930]

Something to consider, I'm not sure if a failing O2 sensor heater can cause lean fuel issue on the 930, it is something that will operate properly once warmed up. Try unplugging it and see what it drives like.

[flightlead404]

Originally Posted by Jhalsey

My symptom is not a miss at high speed or any speed, its a stumble or hesitation that persists and prevents much throttle input until about 4000 rpm. You have to nurse it along. Not consistently, comes and goes. Once it clears, pulls hard with no missing evident. I’m thinking it may be that the vacuum advance is not working. The vacuum advance port holds vacuum but fails to move the rotor. I will look at this more closely when the distributor is out. Also the green wire that carries the trigger signal from the distributor to the CDI unit. My tach is behaving normally.

I'm no Tadek Marek, but in my experience stumbling or hesitation at tip in is more likely mixture related than ignition related.

[Jhalsey]

Just running down the things I find, whether mixture or ignition related. Dead yellow relay, though oddly the new one does not click either w 12 applied across 86/85. Does anyone know the test procedure for this relay? I have applied +12v to 86, neg at 85. With all other relays in my experience, this produces an audible click when the relay contacts close. I know there is a diode wired in somewhere which would make it polarity sensitive.

Plugs sooty but not horrible and clean up easily, gaps all the same, haven't been able to pull the drivers side plugs. They are OE spec W3DP0 Bosch. I have checked the continuity of the green wire between the 6 pin plug and the distributor per the WSM and it tests ok. The internal coil in the distributor has a resistance of 596 Ohms. Spec is 490 to 700 Ohms. I have applied vacuum to the forward facing (away from the Dist) port and pressure to the rearward facing (towards the distributor) and have seen zero movement.

Update midpost! I just removed the vaccum canister and it is now obvious why there is no movement when vacuum/pressure is applied, the arm is rusted solid to the canister housing. Anyone know where I can find a working vacuum canister for an 045 distributor??

Thanks for all the input.I would be nowhere without it. As far as a fuel pressure or wide band oxygen/AFR gauge in the cockpit, no. Its stock and I don't wish to modify it, it's too nice. Perhaps there is something i could hookup temporarily without modifying anything, open to suggestions on that.

I am tempted to perform the "clean and lube distributor service" as detailed in a long post by Gunter.

I have removed the distributor and have a rebuild kit from ************ here. I am hesitant to send my distributor away for 5-7 weeks to have it professionally done. I now know I need a vacuum canister, will probably remove the pulse generator and examine the mechanical advance bits, given the condition of the canister, I'm expecting rust there as well.

[krasuskyp]

again, pull wheels and lowering motor 3-4" via the two x-member bolts up in each top engine bay rear corner will provide greater access to driver's side plugs

fitting a WB02 afr gauge doesn't have to be invasive - weld a bung to your exhaust just after turbo, then run wire (via the grommet in driver/rear floor outer corner) to gauge in... say... glovebox. Not ideal but you can have passenger read it. Pretty critical datapoint to have on one of these

[flightlead404]

Originally Posted by Jhalsey

Just running down the things I find, whether mixture or ignition related. Dead yellow relay, though oddly the new one does not click either w 12 applied across 86/85. Does anyone know the test procedure for this relay? I have applied +12v to 86, neg at 85. With all other relays in my experience, this produces an audible click when the relay contacts close. I know there is a diode wired in somewhere which would make it polarity sensitive.

Plugs sooty but not horrible and clean up easily, gaps all the same, haven't been able to pull the drivers side plugs. They are OE spec W3DP0 Bosch. I have checked the continuity of the green wire between the 6 pin plug and the distributor per the WSM and it tests ok. The internal coil in the distributor has a resistance of 596 Ohms. Spec is 490 to 700 Ohms. I have applied vacuum to the forward facing (away from the Dist) port and pressure to the rearward facing (towards the distributor) and have seen zero movement.

Update midpost! I just removed the vaccum canister and it is now obvious why there is no movement when vacuum/pressure is applied, the arm is rusted solid to the canister housing. Anyone know where I can find a working vacuum canister for an 045 distributor??

Thanks for all the input.I would be nowhere without it. As far as a fuel pressure or wide band oxygen/AFR gauge in the cockpit, no. Its stock and I don't wish to modify it, it's too nice. Perhaps there is something i could hookup temporarily without modifying anything, open to suggestions on that.

I am tempted to perform the "clean and lube distributor service" as detailed in a long post by Gunter.

I have removed the distributor and have a rebuild kit from ************ here. I am hesitant to send my distributor away for 5-7 weeks to have it professionally done. I now know I need a vacuum canister, will probably remove the pulse generator and examine the mechanical advance bits, given the condition of the canister, I'm expecting rust there as well.

any relay will work in place of the yellow one, I ran a regular relay there for years. So, you can swap out a known good relay if needed for testing if you like.

sooty plugs sound like an overly rich mixture to me.

[Jhalsey]

Well, have the distributor apart, thanks to the lengthy 2007 thread started by Gunter, I used a battery terminal puller rather than 2 screw drivers to get the reluctor wheel off without loosing (yet) the little dowel pin. The good news is the mechanical advance mechanism is in good shape, the bad news is the vacuum advance/retard mechanism is rusted solid. I sprayed some penetrant in there but there is little hope it will be healed with no way to open and reseal the canister. Removed the drive gear and installed an additional shim to reduce the axial play.

So I am hunting for a used vacuum canister for an 045 distributor, see pictures below. I have learned of an aftermarket replacement coming to market that resembles the OEM Bosch unit and has a billet housing and some sort of electrical mechanism to operate since it requires 12V, however it is quite expensive even for a Porsche part, last resort for me. So if anyone has a useable canister or any leads please send my way.