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Alex that exactly what we needed here .
OP in the picture Alex posted you will see that orange dust on the fingers of his distributor,
what has been happening is the fingers are slightly bent and will rub on each other,
this could be from worn bushing in the dizzy body or from someone bending the fingers ,
the Roll pin is in the shaft cutout and its only visible when the C clip is removed ,
but you will be able to tell if its missing if you can spin the fingers on the shaft .
... this could be from worn bushing in the dizzy body ...
Worn bushings in the dizzy will let the shaft move eccentrically and make the timing wander. BTDT, not on a Porsche but on the road. From the first noticeable miss at 70 on a freeway to total failure was about 30 miles in the middle of nowhere. I can't remember how much the top of the shaft was moving, but it wasn't much, just noticeable.
Perhaps you might check the shaft wobble you mentioned with a dial gauge. A tiny bit may be acceptable, a little bit is something I'd worry about. Increasing is a reason to replace the bushings or dizzy.
Alex that exactly what we needed here .
OP in the picture Alex posted you will see that orange dust on the fingers of his distributor,
what has been happening is the fingers are slightly bent and will rub on each other,
this could be from worn bushing in the dizzy body or from someone bending the fingers ,
the Roll pin is in the shaft cutout and its only visible when the C clip is removed ,
but you will be able to tell if its missing if you can spin the fingers on the shaft .
Stan do you have any comment on the EGR valve issue I mentioned earlier ?
I will double check but Im pretty sure I cannot move the fingers on the shaft.
Something else I noticed was the contact point in the cap seems to be right at the end of the brass. Is this normal.
Well Im still trying to track this down. I have taken the distributor apart and cleaned and lubed everything. I think that the very small amount of play is probably just fine. This past weekend I did some further testing, including using my new Gunsone Color tune to check my A/F mixture. This worked very nicely and was very simple to use. The mixture was defiantly out of spec. The other items I checked were the coil and the 2 resistors, both of which also seemed to be out of spec. Here are a few photos. As you can see the 4ohm resistor is reading 0.8 and it should be between 0.35 & 0.45. Also the Ignition Coil primary reading between term. 1 & 15 is reading 0.7 and it should be between 0.33 & 0.46. Both these items seem to be out of spec and I should replace them, but are they the culprit ? One other thing I noticed with the color tune plug in place, was that every once in a while there was what appeared to be a missed spark - it was very random though.
Check that you have the correct coil in there. That pretty new blue one may be a "hi perf" replacement on a different car.
When testing the resistors, you'll want to remove one connection from each. Then start by touching the two test leads together to verify the resistance in them before testing the resistor. The test leads on my Fluke might give me a 0.2 Ohm reading when shorted together. If I test the resistor and see 0.7 Ohms, I subtract the 0.2 probe resistance number from the measured number to determine the value of the resistor alone. I don't know if you have the option of forcing the range a little lower, so it offers more decimals. At these extremely low resistance numbers, rounding by the meter becomes significant.
Check that you have the correct coil in there. That pretty new blue one may be a "hi perf" replacement on a different car.
When testing the resistors, you'll want to remove one connection from each. Then start by touching the two test leads together to verify the resistance in them before testing the resistor. The test leads on my Fluke might give me a 0.2 Ohm reading when shorted together. If I test the resistor and see 0.7 Ohms, I subtract the 0.2 probe resistance number from the measured number to determine the value of the resistor alone. I don't know if you have the option of forcing the range a little lower, so it offers more decimals. At these extremely low resistance numbers, rounding by the meter becomes significant.
Dr. Bob - (thanks as always for you help and advice) although the coil may look "new" in the photo, I'm pretty sure its original. Definitely does not look anything like new in real life. I will verify resistance on the tester and then re check the resistors removing one wire first.
I guess my main questions is, even though both these items tested out of spec, do you think either of them being off - is enough to cause the miss fire ?.
Check that you have the correct coil in there. That pretty new blue one may be a "hi perf" replacement on a different car.
When testing the resistors, you'll want to remove one connection from each. Then start by touching the two test leads together to verify the resistance in them before testing the resistor. The test leads on my Fluke might give me a 0.2 Ohm reading when shorted together. If I test the resistor and see 0.7 Ohms, I subtract the 0.2 probe resistance number from the measured number to determine the value of the resistor alone. I don't know if you have the option of forcing the range a little lower, so it offers more decimals. At these extremely low resistance numbers, rounding by the meter becomes significant.
Thanks for putting me straight on this. I checked my tester and it too measured a resistance of between .2 & .3 when shorted together, so after removing the coil and resistors from the car and re testing, I think they are actually all within spec.
So now what ?. Not really sure what is left to test. Could it be the computer ? Maybe the Green wire is bad ? Am I missing anything here ?
Check that spark box on the passenger side under the 14 pin connector.
BradW's car ran fine until about 3000 rpm then misfired like crazy.
The O scope showed a great wave pattern until 3000 rpm then it just fell apart.
Changed the spark box and the problem went away.
It's the first one I ever heard of going bad.
Check that spark box on the passenger side under the 14 pin connector.
BradW's car ran fine until about 3000 rpm then misfired like crazy.
The O scope showed a great wave pattern until 3000 rpm then it just fell apart.
Changed the spark box and the problem went away.
It's the first one I ever heard of going bad.
Ive been wondering about that box - Im Gonna see if I can find someone local who has one and see if I can talk them into letting me switch them out. At this point there really isn't much else left to check.
best bet is to plug your box into a known good running car but if thats not an option put deoxit 100 on the pins of the box,
many have corroded pins
Mark at 928intl was kind enough to send me a used TSZ and a distributor for testing purposes. I installed them one at a time and unfortunately saw no change at all. Seems all thats left is the Coil and or the green wire. As mentioned the green wire appears to be in very good shape and I have checked the resistance on the coil without power and it too seemed ok. Im wondering if its an issue once its under power. Can this be tested ? Could a failing ignition coil cause a misfire issue, only after approx. 2000rpm ?
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