Rough idle and misfire
03-25-2007, 09:42 PM
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Rough idle and misfire I have a 1993 chevy camaro z28 and ive had some problems with a real rough idle lately. when i start the car it shoots right up to 2000rpm them slowly drops to a little over 1000rpm and sputters and misfires like crazy. When i drive it seems like the car is not getting gas up to about 3200rpm then it seems to run fine. Occasionally it will also sputter and misfire in higher rpm's but not as much as the lower. does anyone have any ideas what could be causing this??
03-25-2007, 10:10 PM
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Instead of making a whole new thread -- why not refer to the suggestions in the first one you made. 
https://ls1tech.com/forums/lt1-lt4-modifications/682668-high-end-miss.html
https://ls1tech.com/forums/lt1-lt4-modifications/682668-high-end-miss.html
03-26-2007, 08:54 AM
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Originally Posted by greenmachine94
this is my friends car we are talking about here.. mine was a different problem
Also -- if you tried a search you'd probably be able to find a lot of information leading to how you can try to trouble shoot a misfire or stumble. This is some of the stuff I've told to other people who have asked the same question. I literally copy and pasted from a number of threads, so they are slightly out of context. You should be able to figure them out though. A lot of help can be found in this thread as well:
https://ls1tech.com/forums/showthrea...5&page=1&pp=20
Originally Posted by WhyHelloOfficer
How new is the ignition coil? How new is the wire going from the opti to the ignition coil? Did you use dielectric grease in your spark plug boots when you did your plug wires? Did you make sure your plug wires are routed correctly and are not burnt or cut on pulleys (along the passenger side)?
There are quite a few possibilities that I think a lot of you should look into. Getting a new opti-spark isn't always the solution. Some people have a factory opti last them 140,000 miles. Other guys have had one last 80,000, and the new one fails in 1,000 miles. I hate to say it, but it is hit or miss -- you just have to be thorough with your trouble shooting.
One thing that a lot of you need to look into if you are having a hesitation/stumbling/missfire/running rough/breaking up issue. Look along the passenger side of the intake manifold -- there is a wiring harness that looks like this:
It is the harness that goes from the PCM to the optispark. A lot of the time the harness as it goes down along the front of the block and plugs into the opti, it will be corroded and cracked from heat, moisture, and just being old. Take a look at that, because it very might well be your culprit. A lot of people don't look into it, but realize after they are replacing their opti that it needs to be replaced. Do it once, do it right.
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Dielectric grease just helps with conductivity along with keeping moisture out. It is usually a good rule of thumb to use it anytime you do new plugs or wires. That's why it is sold at any DAP or local parts store as "Tune-up Dielectric Grease."
Have you pulled any plugs and checked them since your issues started? Make sure they aren't fouled?
Start the car at night with the hood open and make sure none of the wires are arching. That could be why you possibly aren't getting enough spark to the cylinder.
Also -- I hate to say it but double and triple check your plug wires and their routing along with all of their connections. I had a set of magnecores ($$$ really expensive wires) on my car I had just put on, and I had some mid-range missfire issues about 3 weeks after I installed them. I swore up and down it wasn't the wires, but when I pulled them out one by one and checked them, sure enough three of them were burnt/cracked. I was positive I routed them correctly, evidently not well enough.
Are you wires over the valve covers or through factory locations? If they aren't OTVC (especially on the passenger side) its possible they got caught on the serpentine belt, or burnt through the factory routing as well.
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If you haven't ever pulled the throttle body off, it probably wouldn't hurt to take it off (get a new gasket between the TB and Intake manifold) and clean it all out. If it has never been cleaned before (trust me, you'll know) then get some rags, some degreaser, and some carb/choke cleaner and just go at it. Just be thorough and get as much of the carbon deposits off of it. Also pull the IAC out and spray and wipe down the pintle (the spring part on the IAC) because that could possibly be causing your partial off-idle hesitation.
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If you've still got your EGR equipment, it could be an EGR or vacuum leak. Double check your EGR equipment and also ensure you don't have any cracked vacuum hoses.
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If the motor has a lot of miles on it, you might want to look into sea foaming it. It is a great way to clean a lot of crap out of there has has built up over a long period of time. To do seafom look here:
https://ls1tech.com/forums/general-maintenance-repairs/534376-how-seafoam-your-car.html
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If your O2 sensors have never been replaced, you might want to look into replacing them as well. If you plan on replacing them, only purchase AC Delco O2 sensors -- do not get the bosch sensors from a local DAP. Typically they don't send readings fast enough for the car to operate well in closed loop.
There are quite a few possibilities that I think a lot of you should look into. Getting a new opti-spark isn't always the solution. Some people have a factory opti last them 140,000 miles. Other guys have had one last 80,000, and the new one fails in 1,000 miles. I hate to say it, but it is hit or miss -- you just have to be thorough with your trouble shooting.
One thing that a lot of you need to look into if you are having a hesitation/stumbling/missfire/running rough/breaking up issue. Look along the passenger side of the intake manifold -- there is a wiring harness that looks like this:
It is the harness that goes from the PCM to the optispark. A lot of the time the harness as it goes down along the front of the block and plugs into the opti, it will be corroded and cracked from heat, moisture, and just being old. Take a look at that, because it very might well be your culprit. A lot of people don't look into it, but realize after they are replacing their opti that it needs to be replaced. Do it once, do it right.
--------
Dielectric grease just helps with conductivity along with keeping moisture out. It is usually a good rule of thumb to use it anytime you do new plugs or wires. That's why it is sold at any DAP or local parts store as "Tune-up Dielectric Grease."
Have you pulled any plugs and checked them since your issues started? Make sure they aren't fouled?
Start the car at night with the hood open and make sure none of the wires are arching. That could be why you possibly aren't getting enough spark to the cylinder.
Also -- I hate to say it but double and triple check your plug wires and their routing along with all of their connections. I had a set of magnecores ($$$ really expensive wires) on my car I had just put on, and I had some mid-range missfire issues about 3 weeks after I installed them. I swore up and down it wasn't the wires, but when I pulled them out one by one and checked them, sure enough three of them were burnt/cracked. I was positive I routed them correctly, evidently not well enough.
Are you wires over the valve covers or through factory locations? If they aren't OTVC (especially on the passenger side) its possible they got caught on the serpentine belt, or burnt through the factory routing as well.
-------
If you haven't ever pulled the throttle body off, it probably wouldn't hurt to take it off (get a new gasket between the TB and Intake manifold) and clean it all out. If it has never been cleaned before (trust me, you'll know) then get some rags, some degreaser, and some carb/choke cleaner and just go at it. Just be thorough and get as much of the carbon deposits off of it. Also pull the IAC out and spray and wipe down the pintle (the spring part on the IAC) because that could possibly be causing your partial off-idle hesitation.
-------
If you've still got your EGR equipment, it could be an EGR or vacuum leak. Double check your EGR equipment and also ensure you don't have any cracked vacuum hoses.
-------
If the motor has a lot of miles on it, you might want to look into sea foaming it. It is a great way to clean a lot of crap out of there has has built up over a long period of time. To do seafom look here:
https://ls1tech.com/forums/general-maintenance-repairs/534376-how-seafoam-your-car.html
-------
If your O2 sensors have never been replaced, you might want to look into replacing them as well. If you plan on replacing them, only purchase AC Delco O2 sensors -- do not get the bosch sensors from a local DAP. Typically they don't send readings fast enough for the car to operate well in closed loop.
03-26-2007, 10:12 AM
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Whyhellofficer that is a good write up. Start with the simple stuff first like plugs and wires. Because if you opti is going out your going to want to replace them anyways.
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03-26-2007, 09:13 PM
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yea sometimes itll run better than others.. there is no check engine light and i checked all my vacuum lines today... im starting to think its the opti more and more everyday
03-27-2007, 08:53 AM
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Originally Posted by greenmachine94
yea sometimes itll run better than others.. there is no check engine light and i checked all my vacuum lines today... im starting to think its the opti more and more everyday
Did you pull the plugs? Are your plug wires all good? Are they arching? Did you use dielectric grease in the plug boots when you installed the plug wires? What condition are your O2 sensors in?
I'm honestly trying to help you -- but if you want to throw money at random parts without checking it out, then knock yourself out.
