Bad bad bad BAD misfire!

[ccapehartusarmyINF.(ret)]

yeah im totally the same way before i bought the tahoe i had i always bought new vehicles the last new vehicle i bought was when i came back from iraq i ordered a brand new ford ranger FX4 with every option possible but im like you i likke to tinker and there aint much to tinker with on a new vehicle so i finally sold it it was paid off and bought the 02 tahoe and i had plenty to do
then i recently got this 01 suburban and theres always something that needs tinkeren
my father tends to rags on my sometimes "when are you gonna be all finished" i have to explain to him that its more like a hobby to me its something i enjoydoing
its not a chore

my goal though is what im calling it the apacalypse suburban fully capable of handling just about any obstacle one mite encounter while roaming the wasteland

 

[#1taho]

yeah im totally the same way before i bought the tahoe i had i always bought new vehicles the last new vehicle i bought was when i came back from iraq i ordered a brand new ford ranger FX4 with every option possible but im like you i likke to tinker and there aint much to tinker with on a new vehicle so i finally sold it it was paid off and bought the 02 tahoe and i had plenty to do
then i recently got this 01 suburban and theres always something that needs tinkeren
my father tends to rags on my sometimes "when are you gonna be all finished" i have to explain to him that its more like a hobby to me its something i enjoydoing
its not a chore

I am with you 100%. My wife thinks my truck is a piece of crap cause I am allways buy something for it and fixing it. She don't understand. But I have less money into my truck than her last three vehicles ! Lol. Oh well. Keep plugging away.

 

[ccapehartusarmyINF.(ret)]

ROLFMAO dude my perents and my brother think the same way they think my vehicles a piece of crap to there snobs they still buy new they dont realize that
i didnt stop financing and buying new vehicles because i couldnt afford to i did it because i got tired of making ford motor credit richer and buy a new vehicle is a bad investment the depreciation right off the lot is absurd
i preferr to use those car payments on maintence or repairs if need be and the upside there is a car payment is do every month
a used vehicle doesnt need a carpayments worth of repairs or maintenence every month

 

[oldsman003]

Still running like hammered dog doo before removing the harness I removed all loom and found perfect wires. Yet another tech hooked it up to his snap on scanner and had no advice. It's going to sound weird but what are symptoms of a faulty temp sensor or sending unit? Within a minute of what the truck now calls "running" the temp gauge was pegged on hot. I'm not familiar with these engines or systems but I know how some little things can cause huge problems. I haven't changed knok sensors as I read more in depth and decided that isn't likely the issue.

 

[ccapehartusarmyINF.(ret)]

so the temp guage almost immediatly shoots up to 260 dagrees ? have you confirmed that is a false reading?

 

[oldsman003]

Yes after less than a minute of running. This whole truck is screwing with my better knowledge as a mechanic.

 

[oldsman003]

I'm almost positive i5 has nothing to do with the immediate runability of the truck but you never know on these new cars so I figured it is worth mentioning. Could be nothing though. I was going to pull the front of the engine apart and check timing but the damn truck starts up so nice even from sitting not running for a month man it doesn't miss a lick firing. But then misses so bad.
From what the scanner shows it misfires the worst on 2,4,6 and does misfire on all cylinders but you just can't tell while it's running. I'm so frustrated

 

[ccapehartusarmyINF.(ret)]

okay if weve already gone over this sorry but has a compression test been done yes ?

 

[oldsman003]

Compression is 125 psi + I just got done installing a new timing set. Was nothing wrong with old one. But since I use and will user this truck to tow with I already had it apart to check timing so I went ahead and swapped it out, dinky little chain I will tell you. Spliced a new coil harness ground in with no luck. What else could cause this problem

 

[ccapehartusarmyINF.(ret)]

on thing that you mite wanna check is the spark plug gap because mine was missing here and there so i changed the plugs and the old ones had like .80 gaps and once i installed new plugs with the correct gap of .40 it runs alot better

 

[#1taho]

SOMEONE help this guy

 

[about20ninj45]

Get yourself an oscilloscope and start checking your injectors. Set your oscope to trigger on falling voltage. Observe your wave forms for any abnormalities.

 

[t_ahan]

i have the GM bible books for the GMT800's i will start flipping through pages and going through the thread and start a check list to the diag. charts in the misfire section......

i bought the books from the publisher for like $600 when i had the entire pass. bank misfiring...

hopefully i find something that we are missing here

 

[oldsman003]

Update as of today, purchased multimeter to check voltage flow to the injectors. Every cylinder missing or not reads between 7.3-7.55 rechecked spark from coils with my trusty Philips head screw driver and good spark (done know how to check voltage on them) random fire on cylinder 5 and 7 dead missing on 1 and 3 and fully firing entirely on bank 1.

 

[oldsman003]

I'm confused about the knock sensors, I have been told bank 2 could be faulty but them at the same time couldn't cause my issue. The plug that connects the knock sensor harness had no power to or from. Don't know if it is normal or not but just another piece of info for someone more knowledgeable

 

[oldsman003]

And also at any given time will run on more cylinders under some throttle than at idle. It barely runs at idle at around 350rpm

 

[oldsman003]

Update, I purchased a better multimeter to recheck my injector readings as well as my coil readings and all check out to over 12v key on power. Pin 1 and pin 40 on both pcm connectors which are grounds I checkedfor continuity and all is fine. Still misfiring constant on cylinders 2 and 4 intermittentmisfire on cylinders 6 and 8

 

[SLCHOE]

Update as of today, purchased multimeter to check voltage flow to the injectors. Every cylinder missing or not reads between 7.3-7.55 rechecked spark from coils with my trusty Philips head screw driver and good spark (done know how to check voltage on them) random fire on cylinder 5 and 7 dead missing on 1 and 3 and fully firing entirely on bank 1.

Update, I purchased a better multimeter to recheck my injector readings as well as my coil readings and all check out to over 12v key on power. Pin 1 and pin 40 on both pcm connectors which are grounds I checkedfor continuity and all is fine. Still misfiring constant on cylinders 2 and 4 intermittentmisfire on cylinders 6 and 8

I'm confused. The first quote states half are firing and half are intermittently firing yet they all firing (this would be bank 1). Your first post said you were misfiring on all of bank 2 (2,4,6,8) . Which cylinders have misfires counted by the ECM (the highest counts)? Which plugs wires are physically firing?

 

[oldsman003]

All plugs are receiving spark, highest misfire counts are cylinders 2, 4 and 6 although every cylinder is missing at some point the said cylinders are missing hundreds of times versus 12 or 14 etc...

 

[oldsman003]

Replaced o2 sensors on both banks, and new plugs on bank 2. Ran on what I feel was 7 cylinders under moderate throttle play. When I let it idle down it barely started running them continued to go on and misfire like It did before. I can remove the injector wires one by one on bank 2 worth no change in idle on cylinders 2, 4, and 6. I remove plug wires on said cylinders and see his conductivity in spark between coils and wires.