Signs of a wiped cam lobe??
09-06-2010, 03:36 AM
#22
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6 months ago, did you change anything around the time when your motor started missing?
Do you know what the code is when it throws the SES light? Only if your car wasn't OBD1 with the OBD2 connector, you might have to go to the dealership to get the code read. IIRC correctly, it should store the code after its thrown. If its not, recreate the miss for them so they can get the code.
While replacing your spark plug wires, I presume you replaced the wire between the opti and the coil? They get brittle after awhile of heat exposure, and if you move them around by changing the opti or coil they can break internally and look fine on the outside. That was a source of a big miss over 5000 rpm for me.
When you new valve springs, did you checked everything with a valve spring height micrometer? It looks like you did when Lloyd helped you out there. Have you looked underneath the valve covers since you adjusted the rockers? Are they still tight? I had troubles finding true TDC with the CC306, and had to find TDC by taking the spark plug out of #1 and feeling for TDC with a screwdriver. Its worth checking over.
Beyond that, I still think your lifters are still suspect, even if they only have 1500 miles on them. One or more of them could have been bad right out of the box. I've had and seen my fair share of parts that are just bad from the factory. Plus they're the only part of the valve train you haven't replaced yet.
Do you know what the code is when it throws the SES light? Only if your car wasn't OBD1 with the OBD2 connector, you might have to go to the dealership to get the code read. IIRC correctly, it should store the code after its thrown. If its not, recreate the miss for them so they can get the code.
While replacing your spark plug wires, I presume you replaced the wire between the opti and the coil? They get brittle after awhile of heat exposure, and if you move them around by changing the opti or coil they can break internally and look fine on the outside. That was a source of a big miss over 5000 rpm for me.
When you new valve springs, did you checked everything with a valve spring height micrometer? It looks like you did when Lloyd helped you out there. Have you looked underneath the valve covers since you adjusted the rockers? Are they still tight? I had troubles finding true TDC with the CC306, and had to find TDC by taking the spark plug out of #1 and feeling for TDC with a screwdriver. Its worth checking over.
Beyond that, I still think your lifters are still suspect, even if they only have 1500 miles on them. One or more of them could have been bad right out of the box. I've had and seen my fair share of parts that are just bad from the factory. Plus they're the only part of the valve train you haven't replaced yet.
09-06-2010, 10:23 AM
#23
Well 6 months ago I had to pull the motor apart and replace the oil pump and the oil gear because it got sheared....I don't remember it missing before that...
I pulled the motor out and replaced all the bottom end bearings, oil pump, and oil pump drive gear.. checked everything else out really well and put it all back together...
I got it running and I don't remember it missing to begin with and one day it just started missing then it went away and then started doing it again and has done it ever since.....
The first set of LS7 lifters I got from Summit had 1 bad one...So I got another set and they prime up good and make no noise.... I don't think its the lifters but I am not ruling out anything at this point...
Yes when I installed the springs I used a micrometer and they are all installed between 1.780 - 1.800
I ran the car for a while then checked the rockers and they still felt good... I had all the plugs out when I adjusted them and used the screw driver technique like you mentioned....
I don't know....I wonder if the cam could somehow be messed up or the harness or PCM.... Maybe a lifter...
Im gonna drive it today and unplug the maf and see if it helps and then unplug the map and see what it does....
I pulled the motor out and replaced all the bottom end bearings, oil pump, and oil pump drive gear.. checked everything else out really well and put it all back together...
I got it running and I don't remember it missing to begin with and one day it just started missing then it went away and then started doing it again and has done it ever since.....
The first set of LS7 lifters I got from Summit had 1 bad one...So I got another set and they prime up good and make no noise.... I don't think its the lifters but I am not ruling out anything at this point...
Yes when I installed the springs I used a micrometer and they are all installed between 1.780 - 1.800
I ran the car for a while then checked the rockers and they still felt good... I had all the plugs out when I adjusted them and used the screw driver technique like you mentioned....
I don't know....I wonder if the cam could somehow be messed up or the harness or PCM.... Maybe a lifter...
Im gonna drive it today and unplug the maf and see if it helps and then unplug the map and see what it does....
09-06-2010, 11:25 AM
#24
6 months ago, did you change anything around the time when your motor started missing?
Do you know what the code is when it throws the SES light? Only if your car wasn't OBD1 with the OBD2 connector, you might have to go to the dealership to get the code read. IIRC correctly, it should store the code after its thrown. If its not, recreate the miss for them so they can get the code.
While replacing your spark plug wires, I presume you replaced the wire between the opti and the coil? They get brittle after awhile of heat exposure, and if you move them around by changing the opti or coil they can break internally and look fine on the outside. That was a source of a big miss over 5000 rpm for me.
.
Do you know what the code is when it throws the SES light? Only if your car wasn't OBD1 with the OBD2 connector, you might have to go to the dealership to get the code read. IIRC correctly, it should store the code after its thrown. If its not, recreate the miss for them so they can get the code.
While replacing your spark plug wires, I presume you replaced the wire between the opti and the coil? They get brittle after awhile of heat exposure, and if you move them around by changing the opti or coil they can break internally and look fine on the outside. That was a source of a big miss over 5000 rpm for me.
.
Yes I replaced the coil wires too when I did the plug swap...
09-06-2010, 04:58 PM
#25
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Ouch. Yeah, try all the simple stuff, see if unplugging the map and maf do anything for you. Then wait to get the cable and see what the code is.
If that's inconclusive, try swapping out your PCM. Get one from a junkyard, throw your KM in it and flash it with your tune. Easy enough to check for it.
If you're thinking somethings wrong with the harness, I'd check to see if all your grounds are good. A wire might have gotten pinched or wandered too close to a header primary when you were putting the motor back in.
I've haven't had any experience trying to track down electrical gremlins, so I'm no help there if it is indeed a harness problem.
If that's inconclusive, try swapping out your PCM. Get one from a junkyard, throw your KM in it and flash it with your tune. Easy enough to check for it.
If you're thinking somethings wrong with the harness, I'd check to see if all your grounds are good. A wire might have gotten pinched or wandered too close to a header primary when you were putting the motor back in.
I've haven't had any experience trying to track down electrical gremlins, so I'm no help there if it is indeed a harness problem.
09-06-2010, 05:09 PM
#26
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I was also thinking maybe it could be the alternator. If its not supplying the correct voltage and high rpm, that could cause it to act wierd on top. I had that happen to me on a 98 mustang gt years ago. I would go full throttle and near redline it would slow up and then keep going. The battery light also went on when i was near redline too. Could be something to look into.
09-06-2010, 05:46 PM
#27
Ouch. Yeah, try all the simple stuff, see if unplugging the map and maf do anything for you. Then wait to get the cable and see what the code is.
If that's inconclusive, try swapping out your PCM. Get one from a junkyard, throw your KM in it and flash it with your tune. Easy enough to check for it.
If you're thinking somethings wrong with the harness, I'd check to see if all your grounds are good. A wire might have gotten pinched or wandered too close to a header primary when you were putting the motor back in.
I've haven't had any experience trying to track down electrical gremlins, so I'm no help there if it is indeed a harness problem.
If that's inconclusive, try swapping out your PCM. Get one from a junkyard, throw your KM in it and flash it with your tune. Easy enough to check for it.
If you're thinking somethings wrong with the harness, I'd check to see if all your grounds are good. A wire might have gotten pinched or wandered too close to a header primary when you were putting the motor back in.
I've haven't had any experience trying to track down electrical gremlins, so I'm no help there if it is indeed a harness problem.
Now that you mentioned grounds, My block is painted black and my heads are painted silver by the machine shop so I am going to pull all my grounds off and grind everything down to bare metal.. I already have a spare PCM that I am going to get flashed...
I will try the MAF and the MAP too and see what happens....
I was also thinking maybe it could be the alternator. If its not supplying the correct voltage and high rpm, that could cause it to act wierd on top. I had that happen to me on a 98 mustang gt years ago. I would go full throttle and near redline it would slow up and then keep going. The battery light also went on when i was near redline too. Could be something to look into.
My battery is in the trunk too so maybe??
Good lord I never though a high rpm miss could give me this much heart ache!
09-06-2010, 06:56 PM
#29
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I Have a good harness on the way.. The harness that I have now has been cut and spliced several times by the old owner so maybe something there....
Now that you mentioned grounds, My block is painted black and my heads are painted silver by the machine shop so I am going to pull all my grounds off and grind everything down to bare metal.. I already have a spare PCM that I am going to get flashed...
I will try the MAF and the MAP too and see what happens....
My battery is in the trunk too so maybe??
Now that you mentioned grounds, My block is painted black and my heads are painted silver by the machine shop so I am going to pull all my grounds off and grind everything down to bare metal.. I already have a spare PCM that I am going to get flashed...
I will try the MAF and the MAP too and see what happens....
My battery is in the trunk too so maybe??
If your wiring harness has been hacked apart, it becomes the #1 suspect. If you got a new harness en route, throw it on before you do anything else. Any low voltage loose connections in the areas of ignition, fuel, or pcm functions can cause trouble. I was going to suggest that you check over the connections with an ohm meter, but since its been hacked apart, I'd install the new harness before doing anything else. And since you moved the harness around while taking out the motor, god knows what could of gotten snapped just due to heat fatigue or bad connections.
You need a good solid 12 volts feeding the computer with no loose connections. If your battery is in the trunk I'd check the the connections there too in addition to getting the grounds down to bare metal.
Last edited by 4K+Converter; 09-06-2010 at 07:52 PM.
09-06-2010, 07:44 PM
#30
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I think it looks like ignition, but I have issues with my own motor, so I'm the wrong guy to ask. lol. But my car breaks up at high rpm also. Brand new gm opti , but untuned cc503 cam all boltons
09-07-2010, 10:21 AM
#31
Ok well here is my next plan of action....
- install New Harness
- Re do all grounds and grind down the Block, Head, chassis grounds down to bare metal...
- Charge the battery over night so I have full voltage
I am also waiting for my tuner to get in touch with me so I can get my spare PCM flashed too.....
If that don't fix it then I am going to pull all the rockers and set up my dial indicator and check all the lobes on the cam....
It is just crazy cause the car pulls great until ~5800 rpms then it starts popping and missing but as SOON as i shift into the next gear it pulls great again until ~5800! However sometimes it will pull to the shift light in 1st (6400) without popping or missing.....
- install New Harness
- Re do all grounds and grind down the Block, Head, chassis grounds down to bare metal...
- Charge the battery over night so I have full voltage
I am also waiting for my tuner to get in touch with me so I can get my spare PCM flashed too.....
If that don't fix it then I am going to pull all the rockers and set up my dial indicator and check all the lobes on the cam....
It is just crazy cause the car pulls great until ~5800 rpms then it starts popping and missing but as SOON as i shift into the next gear it pulls great again until ~5800! However sometimes it will pull to the shift light in 1st (6400) without popping or missing.....
Last edited by MattSapp95_T/A; 09-07-2010 at 10:37 AM.
09-07-2010, 11:11 AM
#32
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try that and if it still does it i would start looking at the alternator. Charging the battery isnt gonna really help any. If the alt isnt supplying the right power at high rpm then the battery takes over which we all know from high end audio that a battery cant take much. keep us updated. I still got money on it being electrical tho. Goodluck!
09-13-2010, 03:05 PM
#34
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Hello, I'm new to this forum but I saw your problem and thought I would post. I had this exact same issue and like you went through my valves over and over again, replaced opti after opti, ran all kinds of test on it, replaced fuel pump, regulator, etc.... finally ended up being the wire harness back behind the intake manifold where it starts to go back to the PCM if I can remember correctly. The wire was the one that ran down to the opti....it was split but still hanging on by the insulation....don't know how or why it split but it was causing the same issues. All that work and once I found it it took me 10 minutes to fix it and it ran fine after that...I would look that harness over very closely
09-13-2010, 06:26 PM
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I will throw my hat into the ring here with just a free/simple suggestion that happened to me. I tucked/hid most of the wires in my engine bay and when I got my car running again, it would run good, but sorta miss up top, I had no idea what to look for. Finally, I read somewhere online that if you MAF wires are too close to an ignition wire, it can cause a problem. What happens specifically with the MAF is that the signals it sends are based on frequency and not voltage- like most things in the car. The high voltage of a spark plug wire can interrupt these signals and cause the car to see bad signals from the MAF. On my car, I had the MAF wire running right next to the wire from the coil to the opti, moved it a few inches away and all was good. Everyone else has had some good ideas also, so good luck and hope you get it sorted out. I have a battery drain that makes me want to pull my hair out.
Bill
Bill
09-13-2010, 08:14 PM
#36
Hello, I'm new to this forum but I saw your problem and thought I would post. I had this exact same issue and like you went through my valves over and over again, replaced opti after opti, ran all kinds of test on it, replaced fuel pump, regulator, etc.... finally ended up being the wire harness back behind the intake manifold where it starts to go back to the PCM if I can remember correctly. The wire was the one that ran down to the opti....it was split but still hanging on by the insulation....don't know how or why it split but it was causing the same issues. All that work and once I found it it took me 10 minutes to fix it and it ran fine after that...I would look that harness over very closely
I will throw my hat into the ring here with just a free/simple suggestion that happened to me. I tucked/hid most of the wires in my engine bay and when I got my car running again, it would run good, but sorta miss up top, I had no idea what to look for. Finally, I read somewhere online that if you MAF wires are too close to an ignition wire, it can cause a problem. What happens specifically with the MAF is that the signals it sends are based on frequency and not voltage- like most things in the car. The high voltage of a spark plug wire can interrupt these signals and cause the car to see bad signals from the MAF. On my car, I had the MAF wire running right next to the wire from the coil to the opti, moved it a few inches away and all was good. Everyone else has had some good ideas also, so good luck and hope you get it sorted out. I have a battery drain that makes me want to pull my hair out.
Bill
Bill
Thanks guys!!
Matt
