engine breaks up at high rpm when warmed up
05-27-2007, 03:03 AM
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engine breaks up at high rpm when warmed up Basically, after my car has fully warmed up and I floor it I can feel the rpms break up around 5k rpm. But when my engine is still cold, it goes through the rpms fine. I was wondering if this is a common problem due to opti, or Knock sensor or the iat getting hotter and pulling timing from the engine. The hotter the engine is the worse it is. Sometimes it will pull and just fall on its face when its real hot. even if the fans are on all the time after the engine is warmed up it still does it slightly. You can really notice it in third and fourth gear, but sometimes I can even notice it in first gear and usually second. when it's like this, my car will actually have better acceleration when I'm at a lower rpm just because it breaks up a lot in the tall gears that take a while to go through. it's been like this since i bought the car 4 mothns ago.
05-28-2007, 08:43 AM
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Basically I've compiled a list of stuff to take a look at from a number of threads of trying to help people resolve a misfire/stumble/hesitation/stall. Take a look and go from there 
It is hard to diagnose a stumble/hesitation/miss on the internet, it can be an extremely wide array of things that are the culprit. I've helped quite a few people with similar issues, and they never came back looking for more help so I'm assuming they solved it.
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
It is hard to diagnose a stumble/hesitation/miss on the internet, it can be an extremely wide array of things that are the culprit. I've helped quite a few people with similar issues, and they never came back looking for more help so I'm assuming they solved it.
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.
05-28-2007, 01:22 PM
#6
so glad i got rid of that EVAP/EGR crap.. im gonna be checking my wires i know 1 is burned for a fact but i dont have this problem all the time
probably replace all my plugs my car had flooded sinec the 6AL went and i had to change my oil/filter due to gas smell
probably replace all my plugs my car had flooded sinec the 6AL went and i had to change my oil/filter due to gas smell
05-29-2007, 02:34 AM
#7
my problem was arching plug wires. They still do it some so i'm gonna be investing in some wires from WS6store.com and see if the Accel's can take car of the problem. along with my boot covers just a thought but take it on a back road when it's BLACK out and pop the hood. Rev it a little and i bet you see a light show. mine only did it when the motor got warm also.
just a thought but take it on a back road when it's BLACK out and pop the hood. Rev it a little and i bet you see a light show. mine only did it when the motor got warm also. Trending Topics
05-30-2007, 02:28 AM
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Originally Posted by ColeTrains'96Z28
my problem was arching plug wires. They still do it some so i'm gonna be investing in some wires from WS6store.com and see if the Accel's can take car of the problem. along with my boot covers just a thought but take it on a back road when it's BLACK out and pop the hood. Rev it a little and i bet you see a light show. mine only did it when the motor got warm also.
just a thought but take it on a back road when it's BLACK out and pop the hood. Rev it a little and i bet you see a light show. mine only did it when the motor got warm also.Interesting...I'll check that out next time I get a chance.
