Car randomly shuts down
10-25-2020, 10:19 PM
#61
Rennlist Member
Thread Starter
That you for that. I did inspect and clean the valley grounds when I replaced the CPS, but it makes sense to give it another look.
Another thing I think I'm going to do is package up the LH, EZF and MAF and send them all to Rich to be tested. Randy and some others have had similar issues that were fixed this way, and Rich mentioned that he is seeing issues with these boxes more and more frequently as they age. If he doesn't find anything I may still have him refresh some of the common failure points he's seeing.
Another thing I think I'm going to do is package up the LH, EZF and MAF and send them all to Rich to be tested. Randy and some others have had similar issues that were fixed this way, and Rich mentioned that he is seeing issues with these boxes more and more frequently as they age. If he doesn't find anything I may still have him refresh some of the common failure points he's seeing.
10-31-2020, 01:38 PM
#62
Former Sponsor
Any closer to figuring this out or are the computers out being checked over?
10-31-2020, 04:33 PM
#63
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As Greg asks, save yourself some trouble and send both the LH and EZK computers to Louis Ott to have them tested.
Odds are very high this is your trouble source.
Odds are very high this is your trouble source.
10-31-2020, 06:51 PM
#64
Former Sponsor
Having "chased" this exact problem a bunch of times....I now "go" to where 90% of the time, this particular problem originates from.
I'm crazy busy and have not had the time to tell you where to look, plus it's a good thing if someone else can come up with a solution. However, although I'm at work on Saturday, I've got 30 minutes or so to tell you where to look:
90% of the time, this complete shut down, with instant restart, will be caused by the secondary coil voltage (coil wire to distributor cap) flashing over to the primary side (signal wire from the computer.) This will instantly shut the car off.....and the car will restart. Doesn't ever seem to "kill" the computer.....just really difficult to find, the first few times yo "see" this.
Because of the plastic "water" coil covers, this "flash over" can be difficult to observe, even in the dark. However, if you listen carefully (and you can get the intermittent part to occur) you will be able to hear the "snap" of the high voltage flashing over. A way to get this to occur quicker is to increase the humidity around the coils wires(and distributor caps)....by "misting" water from a spray bottle in the area.
What causes this to occur is high resistance...somewhere in the spark plug wires or coil wires.
Here's the four obvious sources of this resistance:
1. Incorrect coil wires. Some of the coils have "posts" for the coil wires and some are just open holes. Two different coil designs and two different coil wire designs. You must have the appropriate coil wire for either coil. Amazingly common.
2. Corrosion inside the coil/on the coil wire. Caused by moisture, by #1 above, or by not having the coil wire completely inserted into the coil. Look for "green" or white oxidation inside the coil or on the coil wire. Very common. I've "fixed" multiple cars with this problem, over the phone, from across the country.
3. Improper (cheap aftermarket) coil wires with the incorrect boot. The factory coil wire boot is big enough to "go over" the plastic "water" cap. I've seen many coil wires that have a smaller boot, which will butt up to the plastic cover, but will not go over the cap. This keeps the coil wire from completely plugging in and making good contact causing the spark to "jump". Most all of the original coils have a white line on the secondary post, which tells you how far the stock boot must travel. If there is any doubt, remove the plastic "water" covers and push in the coil wire all the way. Then see if the problem goes away. Very common.
Note: Coil wires are another one of the parts that I exclusively use from Porsche. I throw all of the coil wires that come in spark plug wire sets into the trash and substitute original factory coil wires (yeah, they are ~ $40 each....but "problems" from poor pieces cost more than that!)
4. There are some amazingly bad ignition wire sets. Even Beru sets!!!! The original plug wires threaded into the distributor cap end and the spark plug wire end. Beru (and others) are sometimes supplying wire sets that no longer thread together, but have a wire that "pushes" over the distributor connector. Super easy to pull this wire off of the connector and still have the end of the plug wire captive inside the boot.....so things appear to be normal. This makes the "spark" have to "jump" from the connector to the wire....and once this resistance is higher than the resistance for the coil wire to jump to the primary post, it will. (I've seen this problem, multiple times.) A quick way to check this (other than giving each wire a little tug at the cap) is to measure the resistance of each wire....end to end. (Which you should also do, if you are unsure of the existing spark plug wires/don't know the history.)
I think you will find that one of these individual problems (all resulting in spark jumping to the primary side) are your problem.
Last edited by GregBBRD; 10-31-2020 at 06:53 PM.
10-31-2020, 11:07 PM
#65
Rennlist Member
Thread Starter
Interesting! Thanks for that info. I have the computers out and on the way to be checked. Unfortunately, I don't know anyone here with the same year of car to swap with. I'm not sure how long this will take, so it will be a while before I can run tests, but I will definitely check this out. For what it's worth, I did pull the coil wires off of the coils to look for corrosion, and they looked OK. Mine came with a Beru set that I got 4-5 years ago, for what its worth. I'm going to pull them off again and take a closer look in this area. The fact that you've seen this cause the problem I'm having certainly makes me suspicious that I might also be seeing this.
Intermittent issues are always difficult to find, in the computers....also rare. If I'm in doubt, I find it better to swap in a different set of computers and a different MAF.
Having "chased" this exact problem a bunch of times....I now "go" to where 90% of the time, this particular problem originates from.
I'm crazy busy and have not had the time to tell you where to look, plus it's a good thing if someone else can come up with a solution. However, although I'm at work on Saturday, I've got 30 minutes or so to tell you where to look:
90% of the time, this complete shut down, with instant restart, will be caused by the secondary coil voltage (coil wire to distributor cap) flashing over to the primary side (signal wire from the computer.) This will instantly shut the car off.....and the car will restart. Doesn't ever seem to "kill" the computer.....just really difficult to find, the first few times yo "see" this.
Because of the plastic "water" coil covers, this "flash over" can be difficult to observe, even in the dark. However, if you listen carefully (and you can get the intermittent part to occur) you will be able to hear the "snap" of the high voltage flashing over. A way to get this to occur quicker is to increase the humidity around the coils wires(and distributor caps)....by "misting" water from a spray bottle in the area.
What causes this to occur is high resistance...somewhere in the spark plug wires or coil wires.
Here's the four obvious sources of this resistance:
1. Incorrect coil wires. Some of the coils have "posts" for the coil wires and some are just open holes. Two different coil designs and two different coil wire designs. You must have the appropriate coil wire for either coil. Amazingly common.
2. Corrosion inside the coil/on the coil wire. Caused by moisture, by #1 above, or by not having the coil wire completely inserted into the coil. Look for "green" or white oxidation inside the coil or on the coil wire. Very common. I've "fixed" multiple cars with this problem, over the phone, from across the country.
3. Improper (cheap aftermarket) coil wires with the incorrect boot. The factory coil wire boot is big enough to "go over" the plastic "water" cap. I've seen many coil wires that have a smaller boot, which will butt up to the plastic cover, but will not go over the cap. This keeps the coil wire from completely plugging in and making good contact causing the spark to "jump". Most all of the original coils have a white line on the secondary post, which tells you how far the stock boot must travel. If there is any doubt, remove the plastic "water" covers and push in the coil wire all the way. Then see if the problem goes away. Very common.
Note: Coil wires are another one of the parts that I exclusively use from Porsche. I throw all of the coil wires that come in spark plug wire sets into the trash and substitute original factory coil wires (yeah, they are ~ $40 each....but "problems" from poor pieces cost more than that!)
4. There are some amazingly bad ignition wire sets. Even Beru sets!!!! The original plug wires threaded into the distributor cap end and the spark plug wire end. Beru (and others) are sometimes supplying wire sets that no longer thread together, but have a wire that "pushes" over the distributor connector. Super easy to pull this wire off of the connector and still have the end of the plug wire captive inside the boot.....so things appear to be normal. This makes the "spark" have to "jump" from the connector to the wire....and once this resistance is higher than the resistance for the coil wire to jump to the primary post, it will. (I've seen this problem, multiple times.) A quick way to check this (other than giving each wire a little tug at the cap) is to measure the resistance of each wire....end to end. (Which you should also do, if you are unsure of the existing spark plug wires/don't know the history.)
I think you will find that one of these individual problems (all resulting in spark jumping to the primary side) are your problem.
Having "chased" this exact problem a bunch of times....I now "go" to where 90% of the time, this particular problem originates from.
I'm crazy busy and have not had the time to tell you where to look, plus it's a good thing if someone else can come up with a solution. However, although I'm at work on Saturday, I've got 30 minutes or so to tell you where to look:
90% of the time, this complete shut down, with instant restart, will be caused by the secondary coil voltage (coil wire to distributor cap) flashing over to the primary side (signal wire from the computer.) This will instantly shut the car off.....and the car will restart. Doesn't ever seem to "kill" the computer.....just really difficult to find, the first few times yo "see" this.
Because of the plastic "water" coil covers, this "flash over" can be difficult to observe, even in the dark. However, if you listen carefully (and you can get the intermittent part to occur) you will be able to hear the "snap" of the high voltage flashing over. A way to get this to occur quicker is to increase the humidity around the coils wires(and distributor caps)....by "misting" water from a spray bottle in the area.
What causes this to occur is high resistance...somewhere in the spark plug wires or coil wires.
Here's the four obvious sources of this resistance:
1. Incorrect coil wires. Some of the coils have "posts" for the coil wires and some are just open holes. Two different coil designs and two different coil wire designs. You must have the appropriate coil wire for either coil. Amazingly common.
2. Corrosion inside the coil/on the coil wire. Caused by moisture, by #1 above, or by not having the coil wire completely inserted into the coil. Look for "green" or white oxidation inside the coil or on the coil wire. Very common. I've "fixed" multiple cars with this problem, over the phone, from across the country.
3. Improper (cheap aftermarket) coil wires with the incorrect boot. The factory coil wire boot is big enough to "go over" the plastic "water" cap. I've seen many coil wires that have a smaller boot, which will butt up to the plastic cover, but will not go over the cap. This keeps the coil wire from completely plugging in and making good contact causing the spark to "jump". Most all of the original coils have a white line on the secondary post, which tells you how far the stock boot must travel. If there is any doubt, remove the plastic "water" covers and push in the coil wire all the way. Then see if the problem goes away. Very common.
Note: Coil wires are another one of the parts that I exclusively use from Porsche. I throw all of the coil wires that come in spark plug wire sets into the trash and substitute original factory coil wires (yeah, they are ~ $40 each....but "problems" from poor pieces cost more than that!)
4. There are some amazingly bad ignition wire sets. Even Beru sets!!!! The original plug wires threaded into the distributor cap end and the spark plug wire end. Beru (and others) are sometimes supplying wire sets that no longer thread together, but have a wire that "pushes" over the distributor connector. Super easy to pull this wire off of the connector and still have the end of the plug wire captive inside the boot.....so things appear to be normal. This makes the "spark" have to "jump" from the connector to the wire....and once this resistance is higher than the resistance for the coil wire to jump to the primary post, it will. (I've seen this problem, multiple times.) A quick way to check this (other than giving each wire a little tug at the cap) is to measure the resistance of each wire....end to end. (Which you should also do, if you are unsure of the existing spark plug wires/don't know the history.)
I think you will find that one of these individual problems (all resulting in spark jumping to the primary side) are your problem.
10-31-2020, 11:58 PM
#66
Chronic Tool Dropper
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'87 thru '95 controllers will work as test mules in your car. More important and way safer is that your contollers should run fine in those same year cars.
11-01-2020, 01:39 AM
#67
Rennlist Member
Thread Starter
11-10-2020, 04:03 PM
#68
Rennlist Member
Thread Starter
For what it's worth, the LH and EZF did not fail during testing. I'm having some preventative work done while it's there. The MAF was 25 mV out of spec. Rich said that he usually recommends refurbishing at 30 mV but believes with the Porken chips its more sensitive. I'm going to do it. It doesn't seem like any of these issues are likely responsible for the shut downs, although possibly some poor running issues that continue to crop up may be fixed.
In the mean time, while waiting for the computers and MAF to come back, I pulled the coil wires and took a closer look. They do not look bad to me, but measuring resistance tip to tip (connectors included) I get a little over 1K on one and around 730 ohms or so on the other. I believe they're supposed to be +/- 10% of 1K? Someone correct me if I'm wrong, but that sounds like one is maybe out of spec on the low end. It was acting a bit finnicky as well but I think that's my meter. I'm going to remeasure with another one just to be sure. I'm not sure lower resistance on this wire would be expected to cause the event that Greg described? But it does seem a little suspicious perhaps?
In the mean time, while waiting for the computers and MAF to come back, I pulled the coil wires and took a closer look. They do not look bad to me, but measuring resistance tip to tip (connectors included) I get a little over 1K on one and around 730 ohms or so on the other. I believe they're supposed to be +/- 10% of 1K? Someone correct me if I'm wrong, but that sounds like one is maybe out of spec on the low end. It was acting a bit finnicky as well but I think that's my meter. I'm going to remeasure with another one just to be sure. I'm not sure lower resistance on this wire would be expected to cause the event that Greg described? But it does seem a little suspicious perhaps?
11-10-2020, 05:34 PM
#69
Team Owner
best bet buy 2 new coil wires and replace one side at a time ,
then the one that fails goes into the trash,
the other is a spare.
NOTE dont let the coil wires rub on any part of their run they will begin to short out where they are touching
then the one that fails goes into the trash,
the other is a spare.
NOTE dont let the coil wires rub on any part of their run they will begin to short out where they are touching
11-10-2020, 05:37 PM
#70
Rennlist Member
Thread Starter
That seems like a reasonable thing to do...I'll order them now.
11-16-2020, 11:23 PM
#71
Rennlist Member
Thread Starter
So I have some news. I got my LH, EZF and MAF back, and I also got new coil wires. Because I am interested to see what ends up fixing the problem (if anything does, don't want to jinx myself!) I managed to NOT install the coil wires yet, just the other stuff.
Keep in mind this is LIMITED testing. I basically started it up, ran it for a while, then shut it off. It never shut itself off, and the car ran significantly smoother. None of those little RPM drops, it didn't sound like it was misfiring, none of that. Purred like a kitten. Now, I will need to do more testing, and some actual driving, to be sure. I have a bunch of stuff apart from when I was searching so I have to get it all back together properly. But so far so good!
One funny thing, my headlights only came up part way, I nudged them and they came up all the way, but they don't go down now. Whoopsie. I'll have to see what's going on there, but I DON'T CARE! The car (may) actually be running properly again, which is a huge relief!
Keep in mind this is LIMITED testing. I basically started it up, ran it for a while, then shut it off. It never shut itself off, and the car ran significantly smoother. None of those little RPM drops, it didn't sound like it was misfiring, none of that. Purred like a kitten. Now, I will need to do more testing, and some actual driving, to be sure. I have a bunch of stuff apart from when I was searching so I have to get it all back together properly. But so far so good!
One funny thing, my headlights only came up part way, I nudged them and they came up all the way, but they don't go down now. Whoopsie. I'll have to see what's going on there, but I DON'T CARE! The car (may) actually be running properly again, which is a huge relief!
11-17-2020, 10:45 AM
#72
Rennlist Member
While trouble shooting head light movement, check that the arms that transfer motion to the head lights have circlips on them. The OEM clips can mysteriously dislodge and when the pin works out of its home, the loose arm can puncture your radiator. Search here for other's experience with this.
11-17-2020, 12:32 PM
#73
Team Owner
its also possible the connectors to the computers were dirty use deoxit on them
11-17-2020, 01:10 PM
#74
Chronic Tool Dropper
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^^^ This handy Mrmerlin guidance should be on the Annual Electrical Maintenance schedule even just as PM. OK, maybe every several years. These connectors plus the MAF, CPS, and maybe the hall sensor connector on S4+ cars. There are so many high-impedance circuits in there, all of them way sensitive to even the tiniest bit of corrosion and contact resistance. A few years ago I had a very interesting running problem while out doing errands a few miles from home. My limping-home diagnosis said MAF, so once we were home and the engine cooled some, out came the MAF for a look. Turned out some of the terminals had what looked like a little wax on them. ??? Cleaned it all up, and back to good running again. A few minutes with contact cleaner and an old toothbrush will go a long way to keeping the car reliable enough to actually drive.
11-17-2020, 01:39 PM
#75
Rennlist Member
Thread Starter
I really should have done the DeOxit bit as a matter of course. I know better :-( Also, I do have the replacement circlip part that stays in place.
In any case, the headlights magically go up and down today as planned. I've seen before that when the car sits for a few weeks, not everything works immediately. My passenger window no longer goes up or down, I'm sure I need to take the switch out and clean it.
However, I have a real problem it seems, unrelated to anything electrical. So, my car was sitting for a bit on my somewhat inclined driveway. I had it in 2nd as a precaution if the e-brake cable should break or something. I remember last night it took some effort to get it out of gear. Anyway, with the engine off, I can switch gears just fine. But with it running...I can't get into any gear. This was all working well before I parked the car for the last 3 or 4 weeks.
I replaced the clutch a few months ago, and like Iike I said, it was working well. I really had no trouble with the adjusters on the intermediate plate at the time, I followed the FSM procedure to push them to the rear and that seemed to work fine. Do you think sitting in gear on an incline somehow caused them to move out of adjustment? Can then be so out of adjustment that you can't get the car in gear? This is disconcerting :-(
In any case, the headlights magically go up and down today as planned. I've seen before that when the car sits for a few weeks, not everything works immediately. My passenger window no longer goes up or down, I'm sure I need to take the switch out and clean it.
However, I have a real problem it seems, unrelated to anything electrical. So, my car was sitting for a bit on my somewhat inclined driveway. I had it in 2nd as a precaution if the e-brake cable should break or something. I remember last night it took some effort to get it out of gear. Anyway, with the engine off, I can switch gears just fine. But with it running...I can't get into any gear. This was all working well before I parked the car for the last 3 or 4 weeks.
I replaced the clutch a few months ago, and like Iike I said, it was working well. I really had no trouble with the adjusters on the intermediate plate at the time, I followed the FSM procedure to push them to the rear and that seemed to work fine. Do you think sitting in gear on an incline somehow caused them to move out of adjustment? Can then be so out of adjustment that you can't get the car in gear? This is disconcerting :-(