Engine Rebuild Part 3 (the finale)
02-27-2012, 12:19 PM
#152
Three Wheelin'
Thread Starter
Thanks guys again.
I've removed and cleaned and dismantled the IACV since the rebuild. For anyone who hasn't done this it's surprisingly easy to remove the pin, then twist the magnetic part from the control half and get the insides very clean. Anyhow, yes is very clean and I don't think it is causing this problem. The IACV makes the big adjustments, and the computer makes the smaller ones with timing. The ones that are happening here are problems with the smaller adjustments.
When it goes through one if it's hot idle fits, the ignition timing is fluctuating a little more than normal at idle, and when it stumbles the engine just ramps up the RPM a little, the idle smooths out, and the transition is very smooth, so if it is using the IACV for a larger adjustment it is doing it's job correctly (or the DME is just using timing advance to compensate).
After even more driving (I think I have like 800 miles on the car now since rebuild) the long term fuel adaption has gone to 1.00 for both banks. The power is just phenomenal, I wish I would have done the injectors and new MAF from the get go. It really feels like it's supposed to now. Magic happens above 5k RPM.
Interestingly, the idle fuel trims remain slightly negative, -0.05, but this time when it's stumbling at idle it doesn't seem that it's because of a lack of fuel sensing rich running (with negative short term trims down below set points at -0.1, nearing -0.2). And of course these readings will adjust based on driving conditions. I'm very confident the fuel trim problem is resolved. I'm thinking the problems apparent might have been compounding, the DME perhaps retarding timing because of the idle ignition timing issue, MAF issue, weak injector issue all the while pulling back even more fuel until near CEL status, which I'm sure would have happened if I didn't address the fuel trim issue.
If you see the other thread I've started I'm starting to lean on an issue with cam or crank position sender or flywheel.
What is interesting, something I've noticed since owning the car for 5 years is after a DME reset the cam deviation values take a while to adapt. Bank 1 deviation doesn't move at all and seems to "learn" more quickly than bank 2. Here's what I've observed paying closer attention to the detail. From the other thread I started.
I'm starting to think it could be a cam sensor issue. The cam deviation values for bank 2 are being misreported each time I reset the DME it takes many drive cycles before it "stabilizes". When I first fired the car it read 0 as it always does and then moved to 3 for bank 2. Bank 1 seems to learn more quickly and settles on 3 degrees (hasn't moved yet). Bank 2 initially after DME reset reads 0 degrees and takes while to register but then moves to 1 or 2 or even 3. Still, until enough drive cycles are complete it even will go back to 0 degrees and sometimes even blip to 1 degree at idle, but when in gear the value doesn't change. I'm wondering if this is because of an issue reading reference marks from the flywheel or crank sender. I might just bite the bullet and order up a new cam sensor. I could swap senders between banks, but that is a major pain in the *** since I have to remove the AOS. I would much rather just remove the air con compressor since that is a whole lot easier, and fortunately the sensor (or bank) that is having the issue reading timing.
If I still had my PST2 I would disconnect the bank 2 cam sensor and reprogram to ROW and see if that solves it. Darn. Shouldn't have sold that thing so soon. And on this subject my spare DME exhibits the same issue as well, so I've ruled that out (and also ohmed out the wiring and read 5 volts going to the cam sensors, and ohmed out the crank sender, although that is still suspect).
The actuators and solenoids are brand new, the cam sprockets are one piece, torqued to factory spec using blue loctite, the timing was set using the factory timing tool, the IMS tube received a new LNE ceramic bearing, the teeth on the IMS tube were fine, the chains are all new. I'm confident it is mechanically sound, unless the issue with the CPS is co-related to a problem on the camshaft, perhaps the reference piece has a problem (although I doubt it).
Here's that thread regarding troubleshooting the flywheel:
https://rennlist.com/forums/996-foru...ired-easy.html
I've removed and cleaned and dismantled the IACV since the rebuild. For anyone who hasn't done this it's surprisingly easy to remove the pin, then twist the magnetic part from the control half and get the insides very clean. Anyhow, yes is very clean and I don't think it is causing this problem. The IACV makes the big adjustments, and the computer makes the smaller ones with timing. The ones that are happening here are problems with the smaller adjustments.
When it goes through one if it's hot idle fits, the ignition timing is fluctuating a little more than normal at idle, and when it stumbles the engine just ramps up the RPM a little, the idle smooths out, and the transition is very smooth, so if it is using the IACV for a larger adjustment it is doing it's job correctly (or the DME is just using timing advance to compensate).
After even more driving (I think I have like 800 miles on the car now since rebuild) the long term fuel adaption has gone to 1.00 for both banks. The power is just phenomenal, I wish I would have done the injectors and new MAF from the get go. It really feels like it's supposed to now. Magic happens above 5k RPM.
Interestingly, the idle fuel trims remain slightly negative, -0.05, but this time when it's stumbling at idle it doesn't seem that it's because of a lack of fuel sensing rich running (with negative short term trims down below set points at -0.1, nearing -0.2). And of course these readings will adjust based on driving conditions. I'm very confident the fuel trim problem is resolved. I'm thinking the problems apparent might have been compounding, the DME perhaps retarding timing because of the idle ignition timing issue, MAF issue, weak injector issue all the while pulling back even more fuel until near CEL status, which I'm sure would have happened if I didn't address the fuel trim issue.
If you see the other thread I've started I'm starting to lean on an issue with cam or crank position sender or flywheel.
What is interesting, something I've noticed since owning the car for 5 years is after a DME reset the cam deviation values take a while to adapt. Bank 1 deviation doesn't move at all and seems to "learn" more quickly than bank 2. Here's what I've observed paying closer attention to the detail. From the other thread I started.
I'm starting to think it could be a cam sensor issue. The cam deviation values for bank 2 are being misreported each time I reset the DME it takes many drive cycles before it "stabilizes". When I first fired the car it read 0 as it always does and then moved to 3 for bank 2. Bank 1 seems to learn more quickly and settles on 3 degrees (hasn't moved yet). Bank 2 initially after DME reset reads 0 degrees and takes while to register but then moves to 1 or 2 or even 3. Still, until enough drive cycles are complete it even will go back to 0 degrees and sometimes even blip to 1 degree at idle, but when in gear the value doesn't change. I'm wondering if this is because of an issue reading reference marks from the flywheel or crank sender. I might just bite the bullet and order up a new cam sensor. I could swap senders between banks, but that is a major pain in the *** since I have to remove the AOS. I would much rather just remove the air con compressor since that is a whole lot easier, and fortunately the sensor (or bank) that is having the issue reading timing.
If I still had my PST2 I would disconnect the bank 2 cam sensor and reprogram to ROW and see if that solves it. Darn. Shouldn't have sold that thing so soon. And on this subject my spare DME exhibits the same issue as well, so I've ruled that out (and also ohmed out the wiring and read 5 volts going to the cam sensors, and ohmed out the crank sender, although that is still suspect).
The actuators and solenoids are brand new, the cam sprockets are one piece, torqued to factory spec using blue loctite, the timing was set using the factory timing tool, the IMS tube received a new LNE ceramic bearing, the teeth on the IMS tube were fine, the chains are all new. I'm confident it is mechanically sound, unless the issue with the CPS is co-related to a problem on the camshaft, perhaps the reference piece has a problem (although I doubt it).
Here's that thread regarding troubleshooting the flywheel:
https://rennlist.com/forums/996-foru...ired-easy.html
03-15-2012, 02:15 AM
#153
Three Wheelin'
Thread Starter
Sorry for the lapse from the last update. I've been too busy driving my car. 
1000 miles now, and ready for an oil change.
The stumbling and noises ended up being a two part problem to finally end the saga.
It's 100% sorted. My old DMF was toast, chattering, rattling, etc. The new DMF is soooo smooth, although not balanced, I am probably losing some HP, I might have it balanced (still looking for competent shop).
ALSO my IACV close winding was toast. It was only providing half the resistance it should be and soaking up volts, causing less air than desired at idle (causing rich condition close to idle). That would explain why it was buzzing and getting very hot to the touch. A new IACV cleared that problem up.
RL member FastEddie had a chance to ride in my car today and I think I may have added a few grey hairs to his head. I haven't seen him around here lately but from the looks of my psngr seat afterwards I'm sure he was impressed (joking).
Next thing on the list is a proper alignment and then get her on the dyno. I have a feeling I'm going to be delightfully impressed.
Oh, and I got the UOA results back from the break in oil. LOL., I'll post them in the next couple days...
1000 miles now, and ready for an oil change.
The stumbling and noises ended up being a two part problem to finally end the saga.
It's 100% sorted. My old DMF was toast, chattering, rattling, etc. The new DMF is soooo smooth, although not balanced, I am probably losing some HP, I might have it balanced (still looking for competent shop).
ALSO my IACV close winding was toast. It was only providing half the resistance it should be and soaking up volts, causing less air than desired at idle (causing rich condition close to idle). That would explain why it was buzzing and getting very hot to the touch. A new IACV cleared that problem up.
RL member FastEddie had a chance to ride in my car today and I think I may have added a few grey hairs to his head. I haven't seen him around here lately but from the looks of my psngr seat afterwards I'm sure he was impressed (joking).
Next thing on the list is a proper alignment and then get her on the dyno. I have a feeling I'm going to be delightfully impressed.
Oh, and I got the UOA results back from the break in oil. LOL., I'll post them in the next couple days...
03-15-2012, 12:41 PM
#156
Instructor
You should be able to stick the foam chunks back into the seat with white glue!
Cheers, Ben
03-15-2012, 04:18 PM
#158
Rennlist Member
I can attest that logray's car feels like a turbo.
Without the lag. Impressive!
Now I wish that I had Jake do a 3.4 to 3.6 build last year, even tho it would have doubled my bill.
Without the lag. Impressive!
Now I wish that I had Jake do a 3.4 to 3.6 build last year, even tho it would have doubled my bill.
03-15-2012, 10:01 PM
#159
logan great to see a great ending to all of your hard work. Enjoy.............
03-27-2012, 08:47 PM
#160
Three Wheelin'
Thread Starter
This car is so unbelievably fun to drive again I can't even describe it in words.
The alignment was the icing on the cake. I can't even believe how great the car is, it is totally sorted, and just has more power than I'm comfortable using on the street. I'll have to get it out to AX this spring.
After cancelling the first dyno appt. so I could resolve some issues, I've been shopping around again. I failed to ask the price of the first recommended place, which turned out to be $200 for just a couple pulls. "No tune" I tell them, just want the numbers. "well we have to set it up the same either way, so we're charging you the same". Argh.
There are no less than 5 shops with "open" dyno's in the greater Sacramento area, the one of which who actually works on Porsche's "doesn't do dyno pulls" anymore.
The rest all want between $150 to $200 for just a run or two. Seriously? Are people that desperate? Just because I have a Porsche badge on my hood ???? It seems like a lot to me to strap the car down and stick a couple probes in the tailpipes. Maybe they have a big insurance bill to pay.
The alignment was the icing on the cake. I can't even believe how great the car is, it is totally sorted, and just has more power than I'm comfortable using on the street. I'll have to get it out to AX this spring.
After cancelling the first dyno appt. so I could resolve some issues, I've been shopping around again. I failed to ask the price of the first recommended place, which turned out to be $200 for just a couple pulls. "No tune" I tell them, just want the numbers. "well we have to set it up the same either way, so we're charging you the same". Argh.
There are no less than 5 shops with "open" dyno's in the greater Sacramento area, the one of which who actually works on Porsche's "doesn't do dyno pulls" anymore.
The rest all want between $150 to $200 for just a run or two. Seriously? Are people that desperate? Just because I have a Porsche badge on my hood ???? It seems like a lot to me to strap the car down and stick a couple probes in the tailpipes. Maybe they have a big insurance bill to pay.
03-28-2012, 01:15 AM
#161
Rennlist Member
Now we just need some good driving weather! First Sac Valley Region autocross is 4/22...
03-28-2012, 02:33 PM
#162
Instructor
If you get exact weight of your car and can log acceleration with a gps device, you can work it out. Aero drag can also be worked out as we know the Cd (or just assumed).
03-28-2012, 04:26 PM
#163
Rennlist Member
This car is so unbelievably fun to drive again I can't even describe it in words.
The alignment was the icing on the cake. I can't even believe how great the car is, it is totally sorted, and just has more power than I'm comfortable using on the street. I'll have to get it out to AX this spring.
After cancelling the first dyno appt. so I could resolve some issues, I've been shopping around again. I failed to ask the price of the first recommended place, which turned out to be $200 for just a couple pulls. "No tune" I tell them, just want the numbers. "well we have to set it up the same either way, so we're charging you the same". Argh.
There are no less than 5 shops with "open" dyno's in the greater Sacramento area, the one of which who actually works on Porsche's "doesn't do dyno pulls" anymore.
The rest all want between $150 to $200 for just a run or two. Seriously? Are people that desperate? Just because I have a Porsche badge on my hood ???? It seems like a lot to me to strap the car down and stick a couple probes in the tailpipes. Maybe they have a big insurance bill to pay.
The alignment was the icing on the cake. I can't even believe how great the car is, it is totally sorted, and just has more power than I'm comfortable using on the street. I'll have to get it out to AX this spring.
After cancelling the first dyno appt. so I could resolve some issues, I've been shopping around again. I failed to ask the price of the first recommended place, which turned out to be $200 for just a couple pulls. "No tune" I tell them, just want the numbers. "well we have to set it up the same either way, so we're charging you the same". Argh.
There are no less than 5 shops with "open" dyno's in the greater Sacramento area, the one of which who actually works on Porsche's "doesn't do dyno pulls" anymore.
The rest all want between $150 to $200 for just a run or two. Seriously? Are people that desperate? Just because I have a Porsche badge on my hood ???? It seems like a lot to me to strap the car down and stick a couple probes in the tailpipes. Maybe they have a big insurance bill to pay.
03-28-2012, 10:57 PM
#164
[SIZE="3"]
ALSO my IACV close winding was toast. It was only providing half the resistance it should be and soaking up volts, causing less air than desired at idle (causing rich condition close to idle). That would explain why it was buzzing and getting very hot to the touch. A new IACV cleared that problem up.
ALSO my IACV close winding was toast. It was only providing half the resistance it should be and soaking up volts, causing less air than desired at idle (causing rich condition close to idle). That would explain why it was buzzing and getting very hot to the touch. A new IACV cleared that problem up.
S.
03-29-2012, 12:37 AM
#165
Nordschleife Master
Join Date: Oct 2004
Location: Vacuuming Cal Speedway
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This car is so unbelievably fun to drive again I can't even describe it in words.
The alignment was the icing on the cake. I can't even believe how great the car is, it is totally sorted, and just has more power than I'm comfortable using on the street. I'll have to get it out to AX this spring.
After cancelling the first dyno appt. so I could resolve some issues, I've been shopping around again. I failed to ask the price of the first recommended place, which turned out to be $200 for just a couple pulls. "No tune" I tell them, just want the numbers. "well we have to set it up the same either way, so we're charging you the same". Argh.
There are no less than 5 shops with "open" dyno's in the greater Sacramento area, the one of which who actually works on Porsche's "doesn't do dyno pulls" anymore.
The rest all want between $150 to $200 for just a run or two. Seriously? Are people that desperate? Just because I have a Porsche badge on my hood ???? It seems like a lot to me to strap the car down and stick a couple probes in the tailpipes. Maybe they have a big insurance bill to pay.
The alignment was the icing on the cake. I can't even believe how great the car is, it is totally sorted, and just has more power than I'm comfortable using on the street. I'll have to get it out to AX this spring.
After cancelling the first dyno appt. so I could resolve some issues, I've been shopping around again. I failed to ask the price of the first recommended place, which turned out to be $200 for just a couple pulls. "No tune" I tell them, just want the numbers. "well we have to set it up the same either way, so we're charging you the same". Argh.
There are no less than 5 shops with "open" dyno's in the greater Sacramento area, the one of which who actually works on Porsche's "doesn't do dyno pulls" anymore.
The rest all want between $150 to $200 for just a run or two. Seriously? Are people that desperate? Just because I have a Porsche badge on my hood ???? It seems like a lot to me to strap the car down and stick a couple probes in the tailpipes. Maybe they have a big insurance bill to pay.