When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Did you do an injector balance test to see if they may be clogged ??
hello- today did balance test with otofix lite bi-directional.results consistent across 8cyl
58-59 initial 33-34 drop. P0300 . Didn’t do the resistance check as my multimeter is on the fritz.
did notice that on start up engine runs smoothly but when coolant reaches about 145 the miss becomes noticeable and gets worse approaching 200 degrees. Why no miss in open loop and miss in closed loop? If a vacuum leak , wouldn’t it be present at start up? Are the cats bad or thr O2 censors? Plugs and wires new.
The engine should go into closed loop within a minute or so once the O2’s are heated up but if the PCM detects a misfire it will go into open loop…so do you have a specific cylinder or cylinders misfiring and which ones ??…your scan tool should have misfire monitors…if one bank it may be an O2 sensor “stuck” rich or lean…are the O2’s switching between 200-800mv’s at idle ??…you’re injector balance looks fine…I would clear the misfire codes because the injectors can be disabled and now run the car at idle and see if you stay in closed loop…what are you fuel trims now ??…if you have a vacuum leak your fuel trims will be elevated at idle (over 10%) but as you raise the RPM they will decrease as the manifold vacuum decreases and the leak will not be as great…I tell the guys on here other than changing plugs and wires you don’t have the advanced diagnostic equipment like a labscope to fix a misfire…if the cats were clogged you will be low on power under load and depending how bad it is your IAT may be elevated as well as your MAP sensor…in plain English air can’t get out of the exhaust manifold and is backing up into the intake manifold hence your elevated IAT and MAP.
The engine should go into closed loop within a minute or so once the O2’s are heated up but if the PCM detects a misfire it will go into open loop…so do you have a specific cylinder or cylinders misfiring and which ones ??…your scan tool should have misfire monitors…if one bank it may be an O2 sensor “stuck” rich or lean…are the O2’s switching between 200-800mv’s at idle ??…you’re injector balance looks fine…I would clear the misfire codes because the injectors can be disabled and now run the car at idle and see if you stay in closed loop…what are you fuel trims now ??…if you have a vacuum leak your fuel trims will be elevated at idle (over 10%) but as you raise the RPM they will decrease as the manifold vacuum decreases and the leak will not be as great…I tell the guys on here other than changing plugs and wires you don’t have the advanced diagnostic equipment like a labscope to fix a misfire…if the cats were clogged you will be low on power under load and depending how bad it is your IAT may be elevated as well as your MAP sensor…in plain English air can’t get out of the exhaust manifold and is backing up into the intake manifold hence your elevated IAT and MAP.
I am just learning the otofix feeling my way - don’t know how to check fuel trims. I have one error code, the 0300 and don’t know enough about the scanner to see individual cylinder function. I certainly appreciate your guidance and will clear the 0300 code snd see what happens. Thanks again
I am just learning the otofix feeling my way - don’t know how to check fuel trims. I have one error code, the 0300 and don’t know enough about the scanner to see individual cylinder function. I certainly appreciate your guidance and will clear the 0300 code snd see what happens. Thanks again
May be best to seek out a professional in that case.
OP stopped by this morning to see what's going on with his car...first thing was check the battery and it was fine...next was "relative compression" test with the scope and all looked good there...scanned for codes and saw a P0300 and saw cylinder #3 was intermittently incrementing up from 2-8 misfires running the engine at idle...now the plugs and wires were changed so went to the injector and coil current and all was good there...MMM ??...asked where the plugs and wires were purchased from and the answer was ....Ebay !!...checked the secondary ignition waveform and saw the "firing line" in KV was lower than the good cylinder...then looked at the "spark line" which is the horizontal line where the spark plasma jumps across the spark plug and saw less than 1000 volts...839 volts to be exact...at low cylinder pressures you should see maybe 2-3 thousand volts on a good plug ....where the spark line curls up is where you draw an imaginary vertical line and anything to the left of the line means there is an ignition problem outside of the cylinder...we have an issue outside of the cylinder...removed the plug and saw the porcelain insulator missing and a fine hairline crack...looked at the Ebay plug vs. the OEM plug and as you can see in the picture the font size on the bad plug is different from OEM...moral of the story...DON'T BUY PARTS LIKE THIS FOR YOUR CORVETTE OFF EBAY OR AMAZON !!!....COUNTERFEIT JUNK !!!
I wish I could say this is the first time I've seen this... it's not.
Apparently half of the NGK stuff on ebay is counterfeit as well.
My general rule of thumb for all things automotive:
Auto parts have an extremely low margin, maybe 45% for the most profitable stuff. If you see something being sold by someone for significantly less (more than ~10% off) than competitors, it's either counterfeit or a straight scam.
you can apply the same theory to music related stuff
OP stopped by this morning to see what's going on with his car...first thing was check the battery and it was fine...next was "relative compression" test with the scope and all looked good there...scanned for codes and saw a P0300 and saw cylinder #3 was intermittently incrementing up from 2-8 misfires running the engine at idle...now the plugs and wires were changed so went to the injector and coil current and all was good there...MMM ??...asked where the plugs and wires were purchased from and the answer was ....Ebay !!...checked the secondary ignition waveform and saw the "firing line" in KV was lower than the good cylinder...then looked at the "spark line" which is the horizontal line where the spark plasma jumps across the spark plug and saw less than 1000 volts...839 volts to be exact...at low cylinder pressures you should see maybe 2-3 thousand volts on a good plug ....where the spark line curls up is where you draw an imaginary vertical line and anything to the left of the line means there is an ignition problem outside of the cylinder...we have an issue outside of the cylinder...removed the plug and saw the porcelain insulator missing and a fine hairline crack...looked at the Ebay plug vs. the OEM plug and as you can see in the picture the font size on the bad plug is different from OEM...moral of the story...DON'T BUY PARTS LIKE THIS FOR YOUR CORVETTE OFF EBAY OR AMAZON !!!....COUNTERFEIT JUNK !!!
.
C5 Diag to the rescue.Our venerable Moderator worked magic before my eyes. Carefully explaining each step in the process or elimination which eventually pointed to cyl 3- . When he pulled the plug, the porcelain was very badly cracked. I installed that plug with to much gorilla grip, lol. All praise to C5 Diag. I limped over this morning and flew home on the expressway. Thanks
Had the same problem last year after replacing all my ignition plugs with new AC DELCO plugs during last winter.
I got misfire on cylinder 3 and the secondary voltage from the coil bounced from 0 to over 10Kv instead of a"stable" voltage between 6 and 7 Kv .
Had the same problem last year after replacing all my ignition plugs with new AC DELCO plugs during last winter.
I got misfire on cylinder 3 and the secondary voltage from the coil bounced from 0 to over 10Kv instead of a"stable" voltage between 6 and 7 Kv .
In my case, not having the expertise to diagnose or even understand those voltage spikes, I was so blessed to have C5 Diag doing his magic. I sm truly grateful to him. Peace
In my case, not having the expertise to diagnose or even understand those voltage spikes, I was so blessed to have C5 Diag doing his magic. I sm truly grateful to him. Peace
A DIY’er or professional “parts changer” could have really “gone down the rabbit hole” on this one…you change plugs and wires and you still have an intermittent misfire so now you change coil pack and injector and still a misfire present…a reason why I tell everyone to find a shop with the advanced diagnostic equipment to find the cause…without being able to look at the secondary ignition with the labscope you would never know the plug was bad…you always need to verify that the new part you change operates correctly if you “think” it was bad.
A DIY’er or professional “parts changer” could have really “gone down the rabbit hole” on this one…you change plugs and wires and you still have an intermittent misfire so now you change coil pack and injector and still a misfire present…a reason why I tell everyone to find a shop with the advanced diagnostic equipment to find the cause…without being able to look at the secondary ignition with the labscope you would never know the plug was bad…you always need to verify that the new part you change operates correctly if you “think” it was bad.
well said and don’t amazon or ebay anything. I learned the hard lesson
