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Crossing my fingers for you. If it's working now, it means apparently you had a faulty coil, and your shop either replaced the wrong coil (thus leaving the faulty one there), or else replaced the faulty coil with another faulty coil. Both of those seem a bit unlikely, no?
If the problem remains, I'd suggest again that you get an o-scope & volt meter, and like MarinS4 says, take ownership of the problem yourself. The Repair Manual walks you through much of this stuff.
Just a thought from left field. Since the problem seems to be when the engine is hot could it be vaper-lock where the fuel is getting too hot in the fuel system before it gets to the fuel injectors?
Has the fuel path or any of the sheet metal been changed in such a way that the fuel line is seeing greater amounts of heat?
Is there some fuel line heat shielding that was not replaced when the engine was put back in?
Was an alternate fuel line other than stock used that is less resistant to heat soaking?
Andy
All possible. I'm hoping at this point it was either that both coils should have been replaced (I thought they were) or that since it wasn't OEM it failed at higher temps. It it started a heat related issue it's possible that the current draw increased at that time, causing a cascade that resulted in the computer pulling the timing back.
That would be hard to measure outside of a dyno.
In any case, it hasn't replicated in any of the street tests I did before. What remains is a track test. If I didn't track it, it never would have shown up on the street. Even if I were some sort of fast and furious racer, it wouldn't be the same conditions to replicate it.
Hopefully now I have 3.8 with new cams and cleaned fuel injectors. Hopefully a noticeable difference.
Replaced ignition unit and replaced what I found out was the 1, not 2, coils replaced with an aftermarket coil (grrr.) Replaced with 2 OEM units.
Originally Posted by JPS
All possible. I'm hoping at this point it was either that both coils should have been replaced (I thought they were) or that since it wasn't OEM it failed at higher temps. It it started a heat related issue it's possible that the current draw increased at that time, causing a cascade that resulted in the computer pulling the timing back.
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I'm not sure I'm understanding what was done here. I'm assuming your car has the standard 993 dual coil unit with a dual plug distributor. Are you saying your shop only used ONE of the two factory coils going to one distributor cap and then jury-rigging in some kind of aftermarket coil going to the other distributor cap ? Was this for testing? Even then, with your Ignition unit(s) failing, I can't even imagine doing that, but I ain't no pro mechanic either.
A new Bosch OEM dual coil unit is what, under $200 ? What am I not understanding here?
Andy may be on to something with the hot fuel but, rather than fuel cavitation, you may have fuel starvation due to insufficient fuel delivery or inadequate fuel pick-up. I had a very similar situation with a '95 Mustang Cobra R a few years back. From the get-go, I would go out on track and, for the first 2-3 laps, the car ran strong all the way up to redline. As it got hotter, the car would bog down at around 4000-4500 rpm. This same scenario happened for the next 3-4 events until a great friend, fellow instructor and senior mechanic, Mike Hinkley, solved it. We disconnected the fuel line and ran the pump to measure output. It was 1/3 the rating of the pump. Either the pump was faulty or something was blocking the output. When I got the car home, I emptied the fuel cell by disconnecting the line into a fuel jug and simply running 12v to the pump until the fuel cell was empty. Pulled the pick-up/gauge sender and sock. No debris but decided to measure the height of the assembly vs. the depth of the fuel cell....The pick-up was smack-dab on the bottom of the cell! Fuel starvation was my problem. To solve it, I cut a section of thick wall AL tubing to raise the assembly 1/4 inch thereby giving the pick-up and sock clearance. Upon investigating with FUELSAFE, I found out, that to save money, the Ford engineers made them use the stock pick-up assembly, even the stock filler neck.
I'm not sure I'm understanding what was done here. I'm assuming your car has the standard 993 dual coil unit with a dual plug distributor. Are you saying your shop only used ONE of the two factory coils going to one distributor cap and then jury-rigging in some kind of aftermarket coil going to the other distributor cap ? Was this for testing? Even then, with your Ignition unit(s) failing, I can't even imagine doing that, but I ain't no pro mechanic either.
A new Bosch OEM dual coil unit is what, under $200 ? What am I not understanding here?
G
Can't say for certain. When I looked closer at the invoice, it said 1, which admittedly doesn't make a ton of sense, as I thought they came as a pair, but non-OEM. We replaced both with OEM at significantly more than $200. Like I say, fingers crossed.
Can't say for certain. When I looked closer at the invoice, it said 1, which admittedly doesn't make a ton of sense, as I thought they came as a pair, but non-OEM. We replaced both with OEM at significantly more than $200. Like I say, fingers crossed.
Ah ok, you were mistaken. Our coils come as a pair mounted to a bracket, so your shop indeed replaced both coils, they just used non-OEM apparently. Bosch OEM coil pair runs $200. Seems unlikely they replaced failed coils with another defective pair, so I doubt this solved your problem.
Originally Posted by JPS
Forgot to mention the fuel pump was also changed along the way.
You absolutely need to do a fuel pressure and flow test. IIRC, the Repair Manual walks you thru both. I think Autozone will even rent you a gauge for free.
In my experience, when there's a problem, it's almost certainly caused by something you messed with, not some coincidental failure of something you didn't touch. So if you reinstall an engine and it runs poorly, it's almost certainly not the ignition module or coils or ECU or etc.
A new Bosch OEM dual coil unit is what, under $200 ? What am I not understanding here?
Does anyone other than Bosch even make these? In a Bosch box or in a Porsche Box it is the same source of manufacturing. It is important to know that a Service New part either from the dealer or a warehouse distributor is not in all cases tested to the same extent as an OE installed part as new on the vehicle at the vehicle's manufacturer. Typically once a part becomes a low volume part not installed on any current production vehicles its manufacturing is moved to a different plant a contract manufacturer or the tooling is sold to a third party. For our cars, this becomes apparent where the original part is marked as manufactured in Germany or France and the service replacement part is marked from an Eastern European or Asian country.
EDIT: Looks like they are also or were sold under the BERU brand, not sure if they come from the same plant.
In any case, it hasn't replicated in any of the street tests I did before. What remains is a track test. If I didn't track it, it never would have shown up on the street. Even if I were some sort of fast and furious racer, it wouldn't be the same conditions to replicate it.
Hopefully now I have 3.8 with new cams and cleaned fuel injectors. Hopefully a noticeable difference.
09-08-2019, 12:12 AM
