SwayBar

Does that mean that Steve doesn't put it on an engine/chassis dyno after he builds it?

JPS

I'm in NYC. Steve advised but didn't build.

nine9six

Oh contraire!

JPS, do you happen to have a photo of the valve seat?

JPS

I do not. I went by what a reputable race shop filled with cars made of unobtanium told me. I could have done springs, rods, and bore out 3.8, but drew the line somewhere for my DE level performance.

That said, I will be adding an aux oil cooler as soon as they are back in stock with Gert.

JPS

So, first off, as you can see by the first date of this thread and this date of this post, this has been a long saga. Just sharing as I learned a few things along the way. Some of the things maybe slightly out of order as I frankly don't recall in all the back and forth.

Recap:
Busted valve, planned on rebuild 3.6, took it down to the crank and came back up a tame 3.8. I still want(ed) it streetable, so just cams and slip in 3.8.
Picked it up. Seemed ok. Then oil seepage.
Took it back, seems the RMS didn't get seated properly. Shop fixed.
Brought it home, then oil puddle under the car and passenger rear wheel well coated with oil.
Fixed the oil line as per above.
Winter. Long winter.
Took it to the Glen. Slower than before the build. A) I expected even a 3.6 build would be faster considering that I was down so much on 2 cylinders, let alone then the 3.8.
Brought it back. New saga began.

Shop unplugged one coil, car died. They replaced the coils (one broke in their hand), still would sometimes happen (die). Ignition module bad. Ok, replace ignition module. Running on just one channel, so running on 6 plugs vs. 12 would certainly make the back straight at the Glen slower. Back to the Glen.

Now, after about 20-25 min of hard flogging (running in Red, trying desperately to keep up with those pesky GT3s (and failing miserably)), the car would hesitate on hard throttle over 4k RPM, and sometimes even almost stop revving higher past 5k. Cool off, wouldn't do it again until late in next session. Consistently did each session though. Didn't replicate on the street.

Back to the shop.

Looks like maybe ignition module again. Replaced. I tried to get a loaner ECU, but somewhat understandably no takers. I considered just rebuilding it but hesitant until I knew that was the problem. Replaced fuel pump (it was making noise anyway) and perhaps the issue was fuel related. Took the mechanic with the Hammer hooked up live, timing retarded severely on hard throttle after hot. Consistently.

They hunted forever, put it on the dyno, replicated, then did some of the above fixes, then couldn't replicate on the dyno. Super frustrating in retrospect they didn't street test (once I realized it was 20min+ over 4k, I just drove in a lower gear and then punched it to replicate). When it was doing it, if I pulled over immediately and unplugged one coil, it would die immediately (same coil). So clearly still a channel issue.

Pick the car up. I could replicate it nearly immediately. Took it back to the shop. Now they felt it had to be the ECU. I sent my ECU to Loren at Systems Consulting. While I couldn't convince him to take a deposit and loan me his known good one so I could compare back to back, I did send mine in with the igniter module. He tested and found one channel on the ECU was sending a lower signal for spark to the igniter module. Ok, so that would explain it. He sourced the chip on it, but in the meantime boosted the signal so I could continue to test. Seemed better. But then...

Took it out and flogged it a bit longer. Issue came back. Keep in mind this is with an entirely different ECU. Oh, and I tested with 3 different chips: stock, the 3.6 enhanced one I had from before, plus the new 3.8 one. Testing before I sent my ECU in, then with the known good. Oh, and while I pulled over and was unplugging the coil to test, dropped a socket down under the alternator pulley in 90 degree heat with a blazing hot engine midday in the suburbs. Took me 45 min to find someone home to get a hanger so I could fish out the socket, plus three burned knuckles. And a thumb.

Back to the shop, I think? At some point the shop stopped calling me back. That's all I'll say publicly on that. Steve W and Loren were helping me go through various things at this point too.

I was recommended 2 other shops, one who said, "I'm certain I can fix, but I can't take it until November" and one that said, "Damn, I hate those intermittent things, but bring it up." But it was 2.5 hours away and an Amtrak trip to return. So I did. I made him ride with me for the 30 minutes (it was taking a bit longer now with the improvement from Loren), until it replicated it. "Yeah, that's ****ed up" was his response. Later, as he fixed and tested, he said he was glad I made him ride that long. He thought I was nuts at the time, but then really understood what I was talking about.

They swapped the MAF, made it worse, tested through the O2 sensor spot, drove a bunch, decided to send the injectors out for testing. 2 came back with slightly lower flow (like 68 instead of 72), but also poor patterns. Spark plugs blacker than they liked, as well as inside distributor cap. Cleaned injectors, replaced distributor/rotors/etc (Steve W was worried it might be the Hale sensor, but that was fixed by replacing the distributor), and spark plugs. Drive drive drive. Couldn't replicate.

I flogged it for 2 hours all the way home. I thought perhaps it did a very minor version once or twice, but hard to say on public roads with the imperfections and all that. Time to track it.

By now, no more opps at the Glen, only NJMP. Fine. Rain. But afternoon clears. I do double sessions red/black all weekend to ensure it gets hot and ensure I'm flogging the hell out of it. Runs great all weekend. But I changed computers somewhere over the last few years and can't find the track data on NJMP Thunderbolt (lots on Lightning) so can't compare lap time and segment time/speed. Grr.

This was all with the Loren ECU, so now I have to swap back to my fixed one, and wait until spring to get back to the Glen to test.

Hating life on this one, I have to say.

Sucks that it seems it was perhaps a perfect storm of an unrelated spark issue, but a combo of perhaps poor fuel pumping to poor injectors, with perhaps then a suboptimal spark plug. Very dissatisfying. And I won't know for certain until I see track times at the Glen in the spring. It's specific to that track as that's the only track I went to in the last 2 years, essentially. In 2017 discovered the engine issue in May, took most of the summer to get it built and sorted with the oil issues. 2018 May to discover cutting out, and until October to get it (hopefully) sorted.

I could have just bought a GT3 at this point...

AOW162435

JPS

Yes. Yes it is.

TheOtherEric

Man, so sorry to read about all that. And to not even know what the problem part was, well that's just awful. (At least in my ill-fated turbo adventures, I found my misfire culprit was the spark plugs...). I hope you finally solved it!

Churchill

Sorry JPS, what a nightmare. Few things worse on cars than chasing computer mysteries. Hope it's all sorted out now.

Quadcammer

I would have switched to motec about halfway through. saw you out there at njmp, car seemed like ran good. i had my own ecu issues and it was a frustrating experience.

Good luck

KNS

uniquenamehere

If you had to do it all over again, what direction would you take?

PS - sorry that this happened, but hopefully you're happy with it now.

NC TRACKRAT

"Hindsight is always clearer than foresight".

uniquenamehere

Absolutely... but I'm curious how much better the 3.8 is over the 3.6.

JPS

Thanks man. Indeed. It has soured the whole 993 exuberance, I have to say. Sometimes I'm now like, "F-it. Get me a 991 GT3 and let's just go like stink."

Wouldn't have solved the issue.

Well, I didn't plan on the rebuild. Knowing what I know now I would never make a 3.8 out an otherwise healthy 3.6, unless going way big.
There's sometimes a difference between a great builder and a great investigator/detective in terms of mechanic expertise.
I might have just gone Protomotive Turbo if I was going to go all the way down to the crank anyway. Would have been more $$ for sure, but then I'd have 500 HP.

I am too. I was driving it in May 2017 with 2 down cylinders, and that was after a winter of storage. So it was sometime in 2016 that the engine was fully healthy, or perhaps earlier. So it's sort of hard to compare to "before" with the 3.8 now. It does seem torquier and seems to pull stronger, but it isn't huge. Would never be worth doing a tame 3.8 on a healthy 3.6. Since I needed P&C anyway, the increment was small. When I get to the Glen, I can look at RPM/speed/times by sector and ensure I'm getting something better than I had. Until then, or until I find some Thunderbolt data files, I'm sort of just hopeful it's better.