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I recently bought a 01 z06 and noticed a slight miss the car had. So I bought tr55 plugs (I gapped to .55) and some msd 8.5 wires. After the swap the car now runs worse and is very noticeable. I pulled the plugs back out to look for broken ceramic and I also ohm tested the wires and everything was good there. Any advice as where to look next would be appreciated, thanks (The only mods done to the car are b&b axle back and a cold air)
close the gap to around .040 and see if that helps
Gap is not the problem. The ls1/ls6 can run 40-60 gap no problem, can still be spark related via coil packs but also air/fuel mixture.
Start by cleaning the MAF and Throttle body and check the air filter. Do your basics.
I'm leaning towards a bad coil pack.
Again, Gap has nothing to do with that, I daily my C5 and I drive the $hit out of it as it should be. My LS1 is from the oil burner era and I swap plugs 3 times a year and tried different gaps from 35-60 and they all worked but i felt a difference in power in each one.
Even with a .40 gap on new plugs you wont hear any misfires. Since it got worse after swap I am now 90% sure it's going to be a coil pack. Other 5% MAF and TB, lastly O2 sensors.
You got new plugs and wires so time to cross that out.
1) Coil Packs
2) Clean MAF
3) Clean TB
4) If you marked your old plugs, look at the bad ones and work from that.
5) Give up and take it to a shop
In my case for needing to swap plugs 3x a year at least, I know which cylinders are the worse and it's due to the massive amount of carbon which I am now in need of a Top end rebuild. Then I will blow the engine up and drop in a LS3
Last edited by My Vette Life; 05-02-2019 at 03:58 AM.
I had a slight misfire for several months. Went thru all normal checks but nothing. The problem was.... a large hole in the air system hose. I was really pissed off and took the entire air system off. Vette runs just like new now. Hope this helps???
P.S. Yes I used starter fluid to check for leaks and even used propane looking for a vacuum leak.
Last edited by runner140*; 05-02-2019 at 07:34 AM.
Reason: add p s
Gap is not the problem. The ls1/ls6 can run 40-60 gap no problem, can still be spark related via coil packs but also air/fuel mixture.
Start by cleaning the MAF and Throttle body and check the air filter. Do your basics.
I'm leaning towards a bad coil pack.
Again, Gap has nothing to do with that, I daily my C5 and I drive the $hit out of it as it should be. My LS1 is from the oil burner era and I swap plugs 3 times a year and tried different gaps from 35-60 and they all worked but i felt a difference in power in each one.
Even with a .40 gap on new plugs you wont hear any misfires. Since it got worse after swap I am now 90% sure it's going to be a coil pack. Other 5% MAF and TB, lastly O2 sensors.
You got new plugs and wires so time to cross that out.
1) Coil Packs
2) Clean MAF
3) Clean TB
4) If you marked your old plugs, look at the bad ones and work from that.
5) Give up and take it to a shop
In my case for needing to swap plugs 3x a year at least, I know which cylinders are the worse and it's due to the massive amount of carbon which I am now in need of a Top end rebuild. Then I will blow the engine up and drop in a LS3
I had a slight misfire for several months. Went thru all normal checks but nothing. The problem was.... a large hole in the air system hose. I was really pissed off and took the entire air system off. Vette runs just like new now. Hope this helps???
P.S. Yes I used starter fluid to check for leaks and even used propane looking for a vacuum leak.
Are you talking about the hose for the air pump that goes into the cold air?
I recently bought a 01 z06 and noticed a slight miss the car had. So I bought tr55 plugs (I gapped to .55) and some msd 8.5 wires. After the swap the car now runs worse and is very noticeable. I pulled the plugs back out to look for broken ceramic and I also ohm tested the wires and everything was good there. Any advice as where to look next would be appreciated, thanks (The only mods done to the car are b&b axle back and a cold air)
Misfires can sometimes be difficult to locate...a scan tool will help immensely nailing it down to a particular cylinder...I'd say 70% of misfires are ignition related...mechanical and fuel are the rest...you may have a bad injector...even looking at fuel trims with a scan tool you can tell whether it's fuel or ignition related....ignition misfires show a little higher than normal fuel trims...fuel (injector) misfires will be WAY higher....you have all that excess oxygen in the cylinder that is not burned !!
I guess he means .055" not .55 !!...LOL !!..coils are pretty bulletproof on these motors but with excessive plug gap this it will stress the hell out of the coils....higher current needed to fire the plug with bigger gap...higher current....NO GOOD !!....a good coil at idle will draw roughly 5 amps as pictured here on my 2001 !!
Yeah, I meant.055 lol long day yesterday. Anyways, I’ll regap to .040 after work and see if anything changes. Where can I get a labscope? Never used one before.
Misfires can sometimes be difficult to locate...a scan tool will help immensely nailing it down to a particular cylinder...I'd say 70% of misfires are ignition related...mechanical and fuel are the rest...you may have a bad injector...even looking at fuel trims with a scan tool you can tell whether it's fuel or ignition related....ignition misfires show a little higher than normal fuel trims...fuel (injector) misfires will be WAY higher....you have all that excess oxygen in the cylinder that is not burned !!
Well it’s so bad now that you can feel the whole car shaking at idle and the rpm needle is clearly moving about 100rpms up and down now
Well it’s so bad now that you can feel the whole car shaking at idle and the rpm needle is clearly moving about 100rpms up and down now
With the RPM jumping around like that I'd look for a vacuum leak !!...On my '
01 I found a vaccum leak last year at the PCV connector...you'll find the area around the metal "condensation band" leaking (see arrow in picture)...that's where mine was leaking...you can just pull the PCV hose that goes into the intake manifold and either plug it with a section of hose or your finger and see if the RPM stabilizes...check for any vacuum leaks after the MAF sensor...even a stuck open PCV can cause issues since the PCV is a "metered air leak" !!
Yeah, I meant.055 lol long day yesterday. Anyways, I’ll regap to .040 after work and see if anything changes. Where can I get a labscope? Never used one before.
AES Wave (aeswave.com) make a 1 channel labscope with accessories for around $400.00 I believe...you can get a 2 channel Picoscope with accessories for $1700.00 and a 4 channel for $2250.00...depends on your budget...my Picoscope is my favorite diagnostic tool but interpreting what you are seeing is a science in itself !! !!
Do the simple stuff first. Clean the MAF and TB, Check for vacuum leaks in all the vacuum lines and the entire PCV System.
Carefully look for leaks in the intake air ducting between the MAF and the Throttle body. Any unmetered air will cause big idle and engine AFR issues.
COILS. Our C5 coils are pretty good. You can and should make sure that you have proper voltage to the coils. Look for the PINK WIRE and measure the pink wire to chassis ground. You should see full battery voltage with ignition ON!
On the back of the drivers cylinder head are two black wires with white stripe that terminate into a single eyelet. It bolts to the back of the head. That's the COIL GROUNDS (G-107) Check to see that the wires are intact and the bolt is tight. You will need a mirror and flashlight to properly examine it.
Do the simple stuff first. Clean the MAF and TB, Check for vacuum leaks in all the vacuum lines and the entire PCV System.
Carefully look for leaks in the intake air ducting between the MAF and the Throttle body. Any unmetered air will cause big idle and engine AFR issues.
COILS. Our C5 coils are pretty good. You can and should make sure that you have proper voltage to the coils. Look for the PINK WIRE and measure the pink wire to chassis ground. You should see full battery voltage with ignition ON!
On the back of the drivers cylinder head are two black wires with white stripe that terminate into a single eyelet. It bolts to the back of the head. That's the COIL GROUNDS (G-107) Check to see that the wires are intact and the bolt is tight. You will need a mirror and flashlight to properly examine it.
Probably should of added that I did also clean the MAF but I will check the PCV and voltage on the pink wire. It just seems odd to me that the car now runs worse after plug and wire change
With the RPM jumping around like that I'd look for a vacuum leak !!...On my '
01 I found a vaccum leak last year at the PCV connector...you'll find the area around the metal "condensation band" leaking (see arrow in picture)...that's where mine was leaking...you can just pull the PCV hose that goes into the intake manifold and either plug it with a section of hose or your finger and see if the RPM stabilizes...check for any vacuum leaks after the MAF sensor...even a stuck open PCV can cause issues since the PCV is a "metered air leak" !!
Just seems odd that it got worse after a plug and wire change. The car seems normal on power and there is no CEL. Looked at the current diagnostics on the DIC while car is running and there are no codes
Probably should of added that I did also clean the MAF but I will check the PCV and voltage on the pink wire. It just seems odd to me that the car now runs worse after plug and wire change
You “may” have cracked a plug during installation especially those back cylinders...a little sideways tweak with the socket and that’s all she wrote !!...AND MAKE SURE THOSE PLUG WIRES ARE SEATED FIRMLY !!...you should hear a click when they are !!
You “may” have cracked a plug during installation especially those back cylinders...a little sideways tweak with the socket and that’s all she wrote !!...AND MAKE SURE THOSE PLUG WIRES ARE SEATED FIRMLY !!...you should hear a click when they are !!
Are wires are on firmly. One click on the plug and two on the coil. I did notice however the msd wires have a plastic clip around the connector for the coil and the stock wires do not. Is that of significance or is that just how the msd wires are?
Just seems odd that it got worse after a plug and wire change. The car seems normal on power and there is no CEL. Looked at the current diagnostics on the DIC while car is running and there are no codes
Normally an engine with a vacuum leak will run better at higher RPM’s...less vacuum at higher RPM has less of an effect on the leak overall !!...a vacuum leak will not set a code unless the long term fuel trims go above 23% which means the engine or that bank is receiving 23% more fuel...that’s a lot !!
Are wires are on firmly. One click on the plug and two on the coil. I did notice however the msd wires have a plastic clip around the connector for the coil and the stock wires do not. Is that of significance or is that just how the msd wires are?
Sorry !!...not familiar with the MSD wires...I use the GM red performance wires exclusively !!
05-02-2019, 12:44 AM
Misfire getting worse
