Bad intake cam actuator...
07-12-2011, 09:17 PM
#1
Bad intake cam actuator...
So Ive been having weird timing problems for quite some time now. The engine would throw random codes every now and again in regards to timing, specifically P0016. But then it would clear itsself or after I cleared it the engine would be fine. If the engine really was off then the code would stick and the VVT would be disabled and I'd known for sure there was an issue. I also had random cold start issues were once in a while when I started her up the chain clacked around for a sec like non of the slack the tensioner was supposed to be taking was being taken out, but would quiet down right away which led me to believe my tensioner was somehow loosing its oil pressure while the engine was off and releasing the slack in the chain causing the noise at startup.
So two weeks ago, I changed my oil and when I started her up the noise the chain made was like if I had just rebuilt the engine and I started her up for the first time while the tensioner pressurized. Well, it threw a code P0017 and I knew for sure the timing had skipped because the cam phasers were disabled(VVT off). By this time I was sure the tensioner was bad. So I enlisted the help of my mechanic friend and I bought a new tensioner and we replaced it. Sure enough when we took it apart and we lined everything up it was off by a tooth up top. As some of you know, if the timing is off by only a tooth, the engine actually runs fine but diables VVT so you dont tap a valve. Anyways, we put it back together and started her up with the new tensioner and she was quiet and I thought she was gonna be okay. Well she set the code again but this time for P0016. We took her apart again to check if it had skipped but she lined up perfect. FML right?
I tried different ways of diagnosing what it could be. I replaced the cam phasers with spares, I replaced the cam sensors with spares, I took the timing chain cover off a few times to check the chain and everything matched up fine wich left me stumped. I know usually the P0016 could also mean the crank sensor went bad but the car ran fine and never shut off. The chain did seem to have a little more slack in it than I would like but it wasnt terrible. So the last thing I could think of was that the chain had stretched just enough to cause the timing to be thrown off a bit while under load. Far fetched I know but by this time I was grasping at straws. I went And bought a new chain and the next weekend we took her apart again to replace it. Ive got a bunch of mods plus BNR turbo plus BOV so a dealer visit would have been null.
When we took everything apart to replace the chain the intake cam actuator had to come off, something I havent loosened since I did pistons back at the beginning of last year. Well once the bolt was loose on the actuator we were surprised to find that it had lots of play in it! It could move back and forth enough to throw off the timing a whole tooth! Theres not supposed to be ANY play, even with the cam bolt out. this is what we found:
Anyone ever hear of this happening? I sure would like to know how this could happen on its own? That dowel is pressed in there and I was able to pull it out with my fingers. I was on the edge of disaster. Luckily, one of my friends had a spare head so I borrowed the actuator off the intake cam from that head and slapped it on mine. ZERO play back and forth, just the way its supposed to be. We measured the old chain compared to the new one and there was an indiscernible difference in length so we used the stocker when we put it back together with the new tensioner and Im having no problems whatsoever. She starts and runs like she used to and havent had one bad clackity start so I know the new tensioner is doing its job. Just a heads up I guess for anyone that may be having the same prob.
So two weeks ago, I changed my oil and when I started her up the noise the chain made was like if I had just rebuilt the engine and I started her up for the first time while the tensioner pressurized. Well, it threw a code P0017 and I knew for sure the timing had skipped because the cam phasers were disabled(VVT off). By this time I was sure the tensioner was bad. So I enlisted the help of my mechanic friend and I bought a new tensioner and we replaced it. Sure enough when we took it apart and we lined everything up it was off by a tooth up top. As some of you know, if the timing is off by only a tooth, the engine actually runs fine but diables VVT so you dont tap a valve. Anyways, we put it back together and started her up with the new tensioner and she was quiet and I thought she was gonna be okay. Well she set the code again but this time for P0016. We took her apart again to check if it had skipped but she lined up perfect. FML right?
I tried different ways of diagnosing what it could be. I replaced the cam phasers with spares, I replaced the cam sensors with spares, I took the timing chain cover off a few times to check the chain and everything matched up fine wich left me stumped. I know usually the P0016 could also mean the crank sensor went bad but the car ran fine and never shut off. The chain did seem to have a little more slack in it than I would like but it wasnt terrible. So the last thing I could think of was that the chain had stretched just enough to cause the timing to be thrown off a bit while under load. Far fetched I know but by this time I was grasping at straws. I went And bought a new chain and the next weekend we took her apart again to replace it. Ive got a bunch of mods plus BNR turbo plus BOV so a dealer visit would have been null.
When we took everything apart to replace the chain the intake cam actuator had to come off, something I havent loosened since I did pistons back at the beginning of last year. Well once the bolt was loose on the actuator we were surprised to find that it had lots of play in it! It could move back and forth enough to throw off the timing a whole tooth! Theres not supposed to be ANY play, even with the cam bolt out. this is what we found:
Anyone ever hear of this happening? I sure would like to know how this could happen on its own? That dowel is pressed in there and I was able to pull it out with my fingers. I was on the edge of disaster. Luckily, one of my friends had a spare head so I borrowed the actuator off the intake cam from that head and slapped it on mine. ZERO play back and forth, just the way its supposed to be. We measured the old chain compared to the new one and there was an indiscernible difference in length so we used the stocker when we put it back together with the new tensioner and Im having no problems whatsoever. She starts and runs like she used to and havent had one bad clackity start so I know the new tensioner is doing its job. Just a heads up I guess for anyone that may be having the same prob.
07-12-2011, 10:04 PM
#5
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GM is having issues with their cam phasers in the 2010/2011 model 2.4 SIDI engines. They'll make a horrible clatter on cold start until oil pressure builds up. I've fixed these with a simple oil/filter change per a PI.
Your issue is one that's entirely differently, however.
Your issue is one that's entirely differently, however.
07-12-2011, 10:14 PM
#6
GM is having issues with their cam phasers in the 2010/2011 model 2.4 SIDI engines. They'll make a horrible clatter on cold start until oil pressure builds up. I've fixed these with a simple oil/filter change per a PI.
Your issue is one that's entirely differently, however.
Your issue is one that's entirely differently, however.
07-12-2011, 11:07 PM
#7
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i recommend changing the cam tables in the high rpm range (accross the bottom two rows of cells) to smooth them closer to the far right column this way when you let off the gas the cams dont shift a long distance creating a slamming effect. this also wears out valves and valve seats.
07-13-2011, 11:42 AM
#8
i recommend changing the cam tables in the high rpm range (accross the bottom two rows of cells) to smooth them closer to the far right column this way when you let off the gas the cams dont shift a long distance creating a slamming effect. this also wears out valves and valve seats.
Its got a trifecta tune on there right now that only went through one revision before the timing thing happened. Now that thats fixed Im going to continue the loggint to get it dialed in on 93 with Trifecta.
07-13-2011, 12:57 PM
#9
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had same thing happen to me but you got lucky i didn't broke all of my exhust rockers so i feel your pain. also bent some valves. rebuilding mine right now cause on mine the person who reset my timming fucked it up bad and the car jumped timming bad and spun on the cam
07-13-2011, 01:12 PM
#10
What are your plans? Good luck with it!
07-13-2011, 01:19 PM
#11
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well the worest part is that i had just put wisecos in it so yea kinda pissed about that im just waiting on parts right now to finish sucks cause i want my back been down so long i hate it
07-13-2011, 03:03 PM
#12
Damn! You had wisecos already? Even worse bro. Sorry to hear it. I was THIS close to the same thing hapenning to me. Thank god I caught it before disaster struck. Sucks having the car down for so long. Mine was down for three weeks while I waited for the turbo to arrive so I know how you feel.
07-13-2011, 04:03 PM
#15
i recommend changing the cam tables in the high rpm range (accross the bottom two rows of cells) to smooth them closer to the far right column this way when you let off the gas the cams dont shift a long distance creating a slamming effect. this also wears out valves and valve seats.
Usually only happened on road race cars with repeated full WOT to full decel conditions over a long time period, not commonplace on street cars.
07-13-2011, 07:08 PM
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for lnf's the shift is hard like the ms3's and the cam phasers are soft so they are going first. for anyone buying a new head in rebuild or has thrown a rocker and doing rebuilds i highly recommend a set of arp head studs while your in there and a set of new cam phasers for both cams.
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