Rendom misfire

[ukrkoz]

He needs to catch it with live feed... P0300 randomly shows...

 

[BG1988]

Sorry for a bit of unclear question, I should have taken snap shot, but for now, I'll shoot blank.
I just bought auctioned 2007 Tahoe.
Engine runs a bit rough, not too bad, and there's random misfire code.
Truck is in my pal's shop, I know him since his age 11, he won't lie to me. So far, he replaced plugs and wires, that didn't help.
He showed me 2 chewed up plugs, one has wire inside really exposed. As I said, I should have taken snap shot of those 2 plugs... they are, facing engine, R hand side close to fuel rail, mid way on engine top. One is red and one is grey I believe. Grey is less chewed up, red one is wire fully exposed.
My gut tells me, that's cause of random misfire, but what do I know. I had Ridgeline once, it had very similar situation. Parked outside, rats got to it, started misfiring, dealer replaced some chewed up wires and problem went away.
It's 5.l Vortec engine.
OK, I found pic of same engine and marked grey plug. Red one is hidden deeper towards firewall, can't see in this pic but arrow points roughly where it's at.
Will those cause misfire?

View attachment 271069

Dirty injectors


I played the part cannon game all ready.. on my 6.0L.....


just be careful you can burn out the CAT with the misfire

i used lucas fuel treatment since you can't overdose with it.. I put double the recommend dose (like some others on the market)...


walmart has the gallon size for 25$ which is 4x the qt size ( which 4 qt by it self would be 40$)


you can see the engine firing correctly now no more strong shakes or "off balance firing"
(it's balanced at idle) the fuel trims lowered as well from 10.9 to 7-8 at idle..

i'm assuming the injectors got gummed up from oil getting burned..?


it stopped doing that rapid pause play motion while creeping at idle... also i did a remote start and the engine did not misfire upon a overnight cold start... like it did before...

 

[wsteele]

He needs to catch it with live feed... P0300 randomly shows...

His scan tool probably has a misfire count section by cylinder. It will tell you where the misfires have occurred, but count. Most will have some, but a few might have a lot. Knowing which ones can help you determine sources.

 

[BG1988]

His scan tool probably has a misfire count section by cylinder. It will tell you where the misfires have occurred, but count. Most will have some, but a few might have a lot. Knowing which ones can help you determine sources.

for correct combustion you need correct amount fuel, correct amount of air, correct compression and correct spark...also the timing has to be correct..

boom works perfect missing one of those it will not work correctly even if it's slightly off. it will not work right..

 

[wsteele]

for correct combustion you need correct amount fuel, correct amount of air, correct compression and correct spark...

boom works perfect missing one of those it will not work correctly even if it's slightly off.

I think pretty much everyone understands he is occasionally missing at least one of them.

The point is to see if you can isolate the problem, versus just guessing, like: it is dirty injectors...

 

[BG1988]

I think pretty much everyone understands he is occasionally missing at least one of them.

The point is to see if you can isolate the problem, versus just guessing, like: it is dirty injectors...

it's dirty injectors


I ran chevron with techron from 84,000 miles to 102,000 miles

it did not help

I ran some Fuel injector cleaner fixed it after 30 miles of driving.. Even started up today Perfect no misfire (No cheating i.e remote start yeterday) and quickly turning the key was what i tested today...

no startup misfire.

before i would have to hold it in the start for 5 seconds to prevent teh misfire..(Don't attempt this on your 12volt starter you will DAMAGE IT)



my hybird has a 60,000 watt 80HP 360-VAC starter it's the worlds most powerful engine starter available on the retail market.. it acted at there was a vacuum leak.... as it was always trying to "add fuel"

 

[wsteele]

it's dirty injectors


I ran chevron with techron from 84,000 miles to 102,000 miles

it did not help

I ran some Fuel injector cleaner fixed it after 30 miles of driving.. Even started up today Perfect no misfire (No cheating i.e remote start yeterday) and quickly turning the key was what i tested today...

no startup misfire.

before i would have to hold it in the start for 5 seconds to prevent teh misfire..(Don't attempt this on your 12volt starter you will DAMAGE IT)



my hybird has a 60,000 watt 80HP 360-VAC starter it's the worlds most powerful engine starter available on the retail market.. it acted at there was a vacuum leak.... as it was always trying to "add fuel"

You may be right that multiple injectors are partially clogged. On the other hand, if dirty injectors were always the culprit when a random misfire code was thrown, the code would say “dirty injectors”.

 

[ukrkoz]

"dirty injectors" code?

 

[BG1988]

You may be right that multiple injectors are partially clogged. On the other hand, if dirty injectors were always the culprit when a random misfire code was thrown, the code would say “dirty injectors”.

but if you tried everything else that is all that's left.. Wasting money at chevron I buy from the new Circle K.. clean gas no dirty contamination (aka Sediment ,water?) they just opened I know i'm getting 91 octane at the 91 pump i suspect i was getting lesser grade or contaminated gas at the chevron as the timing was lower then what i'm getting from the circle K station 35-44 advanced timing while the chevron was 30-38 advanced timing .




it's totally worth it for the 91octnae as i'm seeing 20.9MPG in M4 V8 ONLY mode( i do let it auto stop at long traffic lights if i know it's going to be more then 8 seconds)


the timing is very important to maximize power output the more power you can get to the wheels the less gas you use overall..

if everything is working perfectly now compared to putting it in before.... then it must have been dirty injectors you know I have spend 450$ "trying" to fix it....

literally that is the perfect engine start... the engine should start at 1000 rpm to 1050rpm on a overnight cold start..

 

[Fless]

but if you tried everything else that is all that's left.. Wasting money at chevron I buy from the new Circle K.. clean gas no dirty contamination (aka Sediment ,water?) they just opened I know i'm getting 91 octane at the 91 pump i suspect i was getting lesser grade or contaminated gas at the chevron as the timing was lower then what i'm getting from the circle K station 35-44 advanced timing while the chevron was 30-38 advanced timing .




it's totally worth it for the 91octnae as i'm seeing 20.9MPG in M4 V8 ONLY mode( i do let it auto stop at long traffic lights if i know it's going to be more then 8 seconds)


the timing is very important to maximize power output the more power you can get to the wheels the less gas you use overall..

if everything is working perfectly now compared to putting it in before.... then it must have been dirty injectors you know I have spend 450$ "trying" to fix it....

literally that is the perfect engine start... the engine should start at 1000 rpm to 1050rpm on a overnight cold start..

Your RF tire has a dirty injector....