Runnin realy rich le3 383
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Joined: Apr 2014
Posts: 18
Re: Runnin realy rich le3 383
Misfire can be from:
SPARK - worn, fouled, cracked, loose, defective plug; burned wire; coil arcing to ground, weak coil, faulty ICM, faulty cap/rotor, plug wires crossed (wrong cylinder), Opti drive indexed incorrectly..
FUEL - running excessively rich, excessively lean, leaking injector, plugged injector, defective injector, faulty injector wiring.
COMPRESSION (and valve train related issues) - low compression, burned valve, sticky valve, faulty lifter, worn cam lobe.
A lot more but that's all I can think of at the moment.
If they had installed the cam position sensor and it was working, the PCM would set a code telling you if it was a random misfire, or specific cylinder(s) misfire, and provide the misfire count by individual cylinder.
Start by opening the hood up when it's dark, and looking for arcing on wires, coil and distributor. It's hard to see all the wires with them tucked under the manifolds, but it's worth looking.
SPARK - worn, fouled, cracked, loose, defective plug; burned wire; coil arcing to ground, weak coil, faulty ICM, faulty cap/rotor, plug wires crossed (wrong cylinder), Opti drive indexed incorrectly..
FUEL - running excessively rich, excessively lean, leaking injector, plugged injector, defective injector, faulty injector wiring.
COMPRESSION (and valve train related issues) - low compression, burned valve, sticky valve, faulty lifter, worn cam lobe.
A lot more but that's all I can think of at the moment.
If they had installed the cam position sensor and it was working, the PCM would set a code telling you if it was a random misfire, or specific cylinder(s) misfire, and provide the misfire count by individual cylinder.
Start by opening the hood up when it's dark, and looking for arcing on wires, coil and distributor. It's hard to see all the wires with them tucked under the manifolds, but it's worth looking.
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Joined: Mar 1999
Posts: 2,068
From: Kernersville, NC
Re: Runnin realy rich le3 383
Who spec'd the cam for the car? I'm not a cam expert, but I wonder if the duration is more for a "race" car than a hot street car.
If it's popping on the way down from a rev, I think that is unburned fuel entering the exhaust, then is burning in the exhaust. I suppose it might be happening through the intake too...
Are you sure the valves are lashed correctly? The others up top have put you on the right path in checking the basics.....and double checking the timing marks for the crank and cam.
Bad plug wires can have you chase your tail for some time(also a bad opti). A new set may not hurt(if you have not already). I've gone back to simply using AC Delco wires. They go on the plugs easy(no risk of having to manhandle them and tear them up going on the plugs) and are pretty reliable. Also try your best to make sure the opti is working properly.
A sure fire way to know what is going on(electrically) is to scope both opti signals(high and low res) along with the primary and secondary ignition signals....but you will need to find a good automotive tech with access to the proper equipment that knows how to use the tools. Then there is the mechanical, to consider, cause it causes misfires and such as well.
Give LE a call. Ask his opinion on the cam....if it's too radical or not for the street.
Your situation is more complicated given the head and cam changes, but have a look at this....Scanner Danner is an excellent Instructor and Tech. Here is how to evaluate a car for a misfire(watch it on youtube).
The latter half of the first part gets into leak down tests and such. Some really good stuff on how to mechanically check the cylinders for leakage.
If it's popping on the way down from a rev, I think that is unburned fuel entering the exhaust, then is burning in the exhaust. I suppose it might be happening through the intake too...
Are you sure the valves are lashed correctly? The others up top have put you on the right path in checking the basics.....and double checking the timing marks for the crank and cam.
Bad plug wires can have you chase your tail for some time(also a bad opti). A new set may not hurt(if you have not already). I've gone back to simply using AC Delco wires. They go on the plugs easy(no risk of having to manhandle them and tear them up going on the plugs) and are pretty reliable. Also try your best to make sure the opti is working properly.
A sure fire way to know what is going on(electrically) is to scope both opti signals(high and low res) along with the primary and secondary ignition signals....but you will need to find a good automotive tech with access to the proper equipment that knows how to use the tools. Then there is the mechanical, to consider, cause it causes misfires and such as well.
Give LE a call. Ask his opinion on the cam....if it's too radical or not for the street.
Your situation is more complicated given the head and cam changes, but have a look at this....Scanner Danner is an excellent Instructor and Tech. Here is how to evaluate a car for a misfire(watch it on youtube).
The latter half of the first part gets into leak down tests and such. Some really good stuff on how to mechanically check the cylinders for leakage.
Last edited by ACE1252; May 6, 2014 at 02:52 PM.
Thread Starter
Registered User
Joined: Apr 2014
Posts: 18
Re: Runnin realy rich le3 383
Who spec'd the cam for the car? I'm not a cam expert, but I wonder if the duration is more for a "race" car than a hot street car.
If it's popping on the way down from a rev, I think that is unburned fuel entering the exhaust, then is burning in the exhaust. I suppose it might be happening through the intake too...
Are you sure the valves are lashed correctly? The others up top have put you on the right path in checking the basics.....and double checking the timing marks for the crank and cam.
Bad plug wires can have you chase your tail for some time(also a bad opti). A new set may not hurt(if you have not already). I've gone back to simply using AC Delco wires. They go on the plugs easy(no risk of having to manhandle them and tear them up going on the plugs) and are pretty reliable. Also try your best to make sure the opti is working properly.
A sure fire way to know what is going on(electrically) is to scope both opti signals(high and low res) along with the primary and secondary ignition signals....but you will need to find a good automotive tech with access to the proper equipment that knows how to use the tools. Then there is the mechanical, to consider, cause it causes misfires and such as well.
Give LE a call. Ask his opinion on the cam....if it's too radical or not for the street.
Your situation is more complicated given the head and cam changes, but have a look at this....Scanner Danner is an excellent Instructor and Tech. Here is how to evaluate a car for a misfire(watch it on youtube).
The latter half of the first part gets into leak down tests and such. Some really good stuff on how to mechanically check the cylinders for leakage.
2008 Hummer H3 Misfire Case Study (Part 1) - YouTube
If it's popping on the way down from a rev, I think that is unburned fuel entering the exhaust, then is burning in the exhaust. I suppose it might be happening through the intake too...
Are you sure the valves are lashed correctly? The others up top have put you on the right path in checking the basics.....and double checking the timing marks for the crank and cam.
Bad plug wires can have you chase your tail for some time(also a bad opti). A new set may not hurt(if you have not already). I've gone back to simply using AC Delco wires. They go on the plugs easy(no risk of having to manhandle them and tear them up going on the plugs) and are pretty reliable. Also try your best to make sure the opti is working properly.
A sure fire way to know what is going on(electrically) is to scope both opti signals(high and low res) along with the primary and secondary ignition signals....but you will need to find a good automotive tech with access to the proper equipment that knows how to use the tools. Then there is the mechanical, to consider, cause it causes misfires and such as well.
Give LE a call. Ask his opinion on the cam....if it's too radical or not for the street.
Your situation is more complicated given the head and cam changes, but have a look at this....Scanner Danner is an excellent Instructor and Tech. Here is how to evaluate a car for a misfire(watch it on youtube).
The latter half of the first part gets into leak down tests and such. Some really good stuff on how to mechanically check the cylinders for leakage.
2008 Hummer H3 Misfire Case Study (Part 1) - YouTube
Last edited by 97lE383Z; May 7, 2014 at 12:27 AM. Reason: Darn predictive text screwin me up
Registered User
Joined: Mar 1999
Posts: 2,068
From: Kernersville, NC
Re: Runnin realy rich le3 383
Delco wires work fine with my Kooks long tube headers. I have them routed in the stock looms along the bottom of the heads. I think I had to ditch the plug wire holders directly after the opti on both sides(to gain length), but have had no problems burning wires(used wire ties to help too). You just have to take time in the routing to make sure they don't contact the primaries.
I agree with the others that leaks after the Bank 1 O2's are not a big deal in causing your issues. Any leak before the Bank 1 O2's could be an issue. That's not going to be easy to have happen unless your header gaskets are leaking at the heads.
Consider this....the O2's are not used for the first few minutes on a cold engine. If it is having problems cold then, I don't think any kind of exhaust leak is causing your problem.
It would really be helpful if you could data log the car and post up the log for us to see.
I agree with the others that leaks after the Bank 1 O2's are not a big deal in causing your issues. Any leak before the Bank 1 O2's could be an issue. That's not going to be easy to have happen unless your header gaskets are leaking at the heads.
Consider this....the O2's are not used for the first few minutes on a cold engine. If it is having problems cold then, I don't think any kind of exhaust leak is causing your problem.
It would really be helpful if you could data log the car and post up the log for us to see.
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