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You don't have to "muscle" it to get it to jump the tooth, you just have to "finesse" ALL the slack to around the exhaust cam gear while keeping the chain taught around the crank and up to the intake cam........
I ended up loosening the bolts on the scavenge pump sprocket and rotating the exhaust cam back to its correct position. I modified (used an angle grinder) the cam lock tool to fit the cam slots at the front of the engine. I could not for the life of me pull any slack in the timing chain to rotate the sprocket ahead a tooth per Porschetech3's suggestion. Too tricky with only the space through the scavenge pump hole to manipulate the chain. Plus not having the ability to lock the intake cam on bank 2 made me really nervous about trying to slip the chain around.
So ... loosened the four bolts on the scavenge pump sprocket and the exhaust cam actually rotated on its own to find its resting position. I assume a couple of the lobes were resting on the lifters and it just rotated to its natural position for TDC. I nudged it with the tool so it was perfectly aligned with the case seam and the intake cam. I know I'm at the end of my travel on the cam and sprocket, so no more eff ups! Will have to wait for a rebuild to put it all back to normal.
I rotated the crank 12 times to verify timing was still ok (checking all the slots on bank 1 and 2 cams). Put everything back together, disconnected the battery for a while to reset the DME, said a prayer and then fired her up. She ran really smooth!
Plugged in Durametric to verify CAM deviations and misfires (none!). Changed the oil and then took her for a drive. Ran sooooo good. Pulled strong and everything was smooth. Cam deviations were 2.00 left and 0.94 right, which was actually a bit better than before!
I do have two codes P0491 and P0492 for the secondary air pump, so I need to recheck my vacuum lines after moving stuff around, but waaaay better than it was.
I call bull**** on the indy shop in Colorado that insisted my misfires were due to bore scoring and insisting that the engine was in time. Discovered that the green plugs were never pulled to check that. I don't doubt I might have some scoring at 211,000 miles and she's a little tired, but it definitely was not the cause of the misfires.
Anyway, planning to run her for a bit "as is" out of curiosity to see how much further a 211,000 mile engine will go, and save up for a rebuild with Nickies down the road. For now, she pulls strong and runs great. These engines will actually put up with some abuse and try to keep running despite some problems. Hopefully I haven't fried any exhaust valves or exacerbated bore scoring by letting her run like this for a bit.
Thanks everyone for the diagnosis and troubleshooting!! I'm grateful to have dodged a bullet and have learned a lot.
Steve
Last edited by MyFavorite996; 03-11-2023 at 06:02 PM.
It took you long enough I could have had that fixed and on the road in an hour ..(j/k)
This is how you fall in love with a Porsche product. You get your hands dirty, learn a lot about the way they are built/engineered, save a sh*t ton of money, then get to enjoy the drive .......Then when you DO have to dig deep into the pocket, you don't mind....
It took you long enough I could have had that fixed and on the road in an hour ..(j/k)
Haha thanks for nailing the diagnosis! That really put the pieces together for me.
To be fair the car is in my shop 30 min away so that accounted for a bit of delay and multiple trips back and forth.
Next time, I would definitely be faster! It only took me 1 1/2 hours to put it all back together. Experience is cumulative.
Last edited by MyFavorite996; 03-11-2023 at 09:59 PM.
Well done. I am so tired of hearing about stupid shops, crooked shops, incompetent shops. Do it yourself !!!
I agree ... That's the only way to educate yourself. I was planning on spending $25k with them on the rebuild, but if they couldn't be thorough on this diagnosis, it makes me question how thorough the rebuild would be. So they probably lost my $
I agree ... That's the only way to educate yourself. I was planning on spending $25k with them on the rebuild, but if they couldn't be thorough on this diagnosis, it makes me question how thorough the rebuild would be. So they probably lost my $
If I were you I would drive your car back to that shop and explain that you fixed it yourself. Let them know you are/were disappointed with their diagnosis and that you will take future business elsewhere . No reason to be confrontational just explain calmly what you feel . Maybe ......... Just maybe they will think twice in the future . Congratulations on the repair !
“I call bull**** on the indy shop in Colorado that insisted my misfires were due to bore scoring and insisting that the engine was in time. Discovered that the green plugs were never pulled to check that. I don't doubt I might have some scoring at 211,000 miles and she's a little tired, but it definitely was not the cause of the misfires.”
Hooray! I’ve been following this thread and am super happy for you! This is a great forum.
Hey thanks! I'm glad to share the resolution. Often these threads start and there is no conclusion, leaving everyone hanging. This is great forum with tons of collective knowledge and wisdom.
If I were you I would drive your car back to that shop and explain that you fixed it yourself --WITH HELP FROM RENNLIST FORUM --. Let them know you are/were disappointed with their diagnosis and that you will take future business elsewhere . No reason to be confrontational just explain calmly what you feel . Maybe ......... Just maybe they will think twice in the future . Congratulations on the repair !
This was a VERY unusual problem that seldom ever happens and is difficult to diagnose due to the DME has no idea where the exhaust cam timing is because there is no Sensor on the exhaust cam , and fault codes sending the diagnosis in the wrong direction.. In a case like this you have to go back to "old school diagnosis": and use fault codes with a grain of salt...
I was Top Trouble Shooter in Dealerships since the early 80's and these were the kind of things that got sent to me after everyone else gave up...
So I don't fault the shop for not being able to find this one....( Yellow Cab is right, too many fingers get pointed at shops being incompetent)
AND a LOT of this success goes to the OP for being so detailed in his background of the event and the symptoms, and being able to follows advice and sticking with it. If it had been someone with less wherewithal this would have been another one of those threads that got left hanging...( the car would have gotten sold, traded off, a new engine ..ect)
Glad it was saved....enjoy !!! .....Put some more miles on that baby and see how far it will go....
Here is another very unusual case of a GT3 that had low power.. It had been on a Dyno and at 3 different Indy shops and 3 Porsche dealers and was fixing to be "bought back" by Porsche if it couldn't be fixed...
There were no fault codes ( except sometimes it would set cam timing codes, but cam timing was perfect)........Various Sensors were replaced, Cam timing was checked and re-checked multiple times, compression test, cylinder leak down test..ALL tests showed good but engine was down on Power....
Then it was sent to me as a last chance before being bought back or an new engine ( customer was running out of patience)..
This is what I found...
Ring on flywheel had slipped
The ring on the DMF flywheel has slipped.....it is a 60-2 ring.........
The way I verified the problem was I removed the #1 coil from the plug and installed an "old school plug wire", then hooked up an "old school timing light" and shot the ignition timing and compared it to the Digital Computer Timing and seen that the Digital Computer Timing was marginally off from the Old School Timing Light, so I removed the DMF and ordered a New DMF to compare....The difference was remarkable...
Last edited by Porschetech3; 03-12-2023 at 07:14 PM.
03-10-2023, 05:22 PM
