I talked to scot w. by phone yesterday (Monday) and he thinks that the cam may be bad. We have run the engine with the valve covers off and could not tell any difference in valve movement, but will check with a dial indicator. There is no valve train noise. I have had 2 motors in the past, not GN 3.8's or turbo motors, with bad cams, and do not remember a dead miss in either.
GN repair shop in Knoxville, TN.
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scot w.
GNSperformance.com
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Tom it was nice talking to you. If you need any help feel free to give me a shout.
Tom you also might want to mention to everyone here that you have a big power loss and the car is a dog. Thats what moved me towards the cam, That and having 180,000mi on it.
You mentioned that when it had the stock turbo on it, It would go down the road sideways as long as you wanted it to, Well it seemed to make good power back then but doesn't anymore. Something went bad or wore out over time since then.
You replaced the valve springs about 60,000mi ago (I asked what LB they were because that could have been a contributing factor on wearing out the cam!!)
You replaced and switched out just about everything else electrical on the car and it's still there. Makes me think it's internal now..
Just a thought,
Scot W.
Darrell_sb2
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Just thought I would let everyone know I am the one who has been helping Tom work on his car. I am going to pull the valve covers and check the cam next. I will try and list everything I have done to the car.
new timing chain , tried different injectors , rebuilt turbo, new egr valve, 3 sets of new plugs, three sets of new plug wires, three different coils packs and modules , computer off of good running car, four different chips, extra grounds strait from the battery , new intake gasket, leak down and compression test, new crank trigger, new temp sensor, cleaned intake and plenum, checked all wiring for cuts and breaks, cleaned all wiring connections, changed torque converter, new iac, set tps with scan tool, new o2 sensor.
thats all I can think of at the moment will add anything else i remember
new timing chain , tried different injectors , rebuilt turbo, new egr valve, 3 sets of new plugs, three sets of new plug wires, three different coils packs and modules , computer off of good running car, four different chips, extra grounds strait from the battery , new intake gasket, leak down and compression test, new crank trigger, new temp sensor, cleaned intake and plenum, checked all wiring for cuts and breaks, cleaned all wiring connections, changed torque converter, new iac, set tps with scan tool, new o2 sensor.
thats all I can think of at the moment will add anything else i remember
83ttypecooled
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Hi,
I have been following this issue,and I believe the cam, which you say is stock,is at fault. I would run another compression test. I had a similar problem,and could hear it in the cranking cycle;I have a wrenches hearing ,but a gauge is the best bet for this.
In my situation,the motor had 92K on it,and cylinders #3 and 6 were low on compression. A leak down test will not help in this situation. I rebuilt the motor,and when the cam came out, I could see the problem easily. I measured the offending lobes;they were down at least 0.2".I'll bet I went through a lot of time and money for a little bit of return,but the result is a flawlessly running vehicle.
Replace the cam with Comp's mildest hydraulic flat tappet,and use additive ZDDP initially,and on oil changes,and your motor will outlive you. Good luck!
I have been following this issue,and I believe the cam, which you say is stock,is at fault. I would run another compression test. I had a similar problem,and could hear it in the cranking cycle;I have a wrenches hearing ,but a gauge is the best bet for this.
In my situation,the motor had 92K on it,and cylinders #3 and 6 were low on compression. A leak down test will not help in this situation. I rebuilt the motor,and when the cam came out, I could see the problem easily. I measured the offending lobes;they were down at least 0.2".I'll bet I went through a lot of time and money for a little bit of return,but the result is a flawlessly running vehicle.
Replace the cam with Comp's mildest hydraulic flat tappet,and use additive ZDDP initially,and on oil changes,and your motor will outlive you. Good luck!
scot w.
GNSperformance.com
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Any updates?
We haven't heard from anyone on how things are going, Post up with the findings.
Scot W.
We haven't heard from anyone on how things are going, Post up with the findings.
Scot W.
UPDATE...Darrell has been sick, and I have been working every day. We should get the cam/valve lift checked this weekend. I don't know just what the valve lift should be, so we will be looking for a difference in lift between valves.
The car did run sideways with the stock turbo and the stretch intercooler, not quite as sideways when I put the TE-44 on. Car stayed that way for two or more years, maybe even three, don't remember. But somewhere along the way it started missing, and I just let it go. The car did not have as mush power but lost it slowly and you just don't notice it as much. Then the night at the drag strip and the car wouldn't fall out of a tree ( 10's in the 1/8 mile ).
Since then we have repaired the TE-44 turbo (bearings were bad) and the car does run better, but still the miss and yes, down on power. THANKS for the help and we should know something soon.
The car did run sideways with the stock turbo and the stretch intercooler, not quite as sideways when I put the TE-44 on. Car stayed that way for two or more years, maybe even three, don't remember. But somewhere along the way it started missing, and I just let it go. The car did not have as mush power but lost it slowly and you just don't notice it as much. Then the night at the drag strip and the car wouldn't fall out of a tree ( 10's in the 1/8 mile ).
Since then we have repaired the TE-44 turbo (bearings were bad) and the car does run better, but still the miss and yes, down on power. THANKS for the help and we should know something soon.
scot w.
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Hope he feels better soon,
Tom as much as you just want to solve this issue with that many miles (180,000) I think the best thing for it at this point would be a nice rebuild. Then everything can be gone though and hopefully run across the problem. But if I was a guessing, it is the cam.
Scot W.
Darrell_sb2
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ok I have checked the cam on the passengers side and everything seems to be fine, I am going to do some more checking tonight and see what I find. I am thinking maybe a cracked head or head gasket...
Darrell_sb2
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Ok me and Tom checked the cam out tonight and we see nothing wrong with it. I am going to put it all back together and look for someone in the area that has and can use an osiliscope, so we can find exactlly were the miss is and go from there.
OK,...I have made arangements to take the GN to the GM dealer tomorrow, 4-30-09, and have them put it on an ocilloscope, so that I will "hopefully" know for sure just where the miss is. I would like to know if it is just one cyl., two cyls. off of the same coil, or is it random. Again, I hope I know tomorrow, and thanks for the help I have received!!!!!!!!!!!!
scot w.
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This may or may not help, but..... Your symtoms sound EXACLTLY (dead mis most of the time, but occasionally not) like what I have been suffering the last couple days.
After checking to make sure all plug wires were well connected, I "think" I saw that wires #2 and 4 were crossed. I have no idea how or when that happened. They were either crossed and it was fixed when I put them back on, or there was just a bad connection and re-securing all wires at both ends fixed it.
Double and tripple check all your plug wires, and make sure the plug they go to matches what's printed next to the coil tower.
Darrell_sb2
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This may or may not help, but..... Your symtoms sound EXACLTLY (dead mis most of the time, but occasionally not) like what I have been suffering the last couple days.
After checking to make sure all plug wires were well connected, I "think" I saw that wires #2 and 4 were crossed. I have no idea how or when that happened. They were either crossed and it was fixed when I put them back on, or there was just a bad connection and re-securing all wires at both ends fixed it.
Double and tripple check all your plug wires, and make sure the plug they go to matches what's printed next to the coil tower.
I have checked them everytime i put them on and even a few times after that, I do know it runs real bad if two of them get crossed up......Just checked them again tonight and they are all in the right locations...of to the dealer in the morning it goes..
GM dealer could not do the oscilliscope test. The machine they had was for a car with a distributor. The machine they had for distribrless ignition was broken. They ran some other test and said there was nothing wrong with the ingition system. After they were told all that had be done to the car, they recomemded to just pull the heads and see.
Before I tear into the engine I may go to BG first.
Before I tear into the engine I may go to BG first.
