1500 suburban, engine misses badly under load, eg uphill or towing boat. Scan shows "number 6 misfire," all elec checked ok, so I did compression check; #6 less than 25 lbs! Valve stuck open? is only fix a valve job? What will I have to spend if valve job needed? Thanks in advance!
I have had the same problem on several chevrolets in the past. The problem was either a broke rocker on the valve trane or the most common is a flat cam lobe. A flat cam lobe will not let the valve open fully or not at all.
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you drove with scan tool running did you to see if you get
any P03xx codes on the FLY? yes/no
some can pop in and out fast.!
missing that fact ,misses the boat.
if engine is not misfiring then its a/t
the TCC lock up only happens under very specail set of rules
light loads. if you learn that (off FSM chart) you can drive
car such that TCC is defeated and if it misfires now ,its the engine
do a tune up in last 9 years>? full engine tune up.
and check trans levels too.
if random , you need to use the scan too better.
driving, you get wife to drive and you scan, see?
the PCM will report many things, but you need to drive it.
my cheap scan tool can log for hours. and can come one
and see all live streaming data (PID's) and all DTCs during that time
sitting at my desk. (omg, the crank sensor burped, 6 times)
no spark from coilpack bad ignition wire and or spark plug.scan test find which cylinder is missing.there is a service bulletin from g.m. on misfires 5.3L engines.possible carboned buildup piston rings.cylinders walls need to be inspected for abnormal wear.my need new short block.
The computer can't sense movement. An engine with worn spark plugs or bad coils can run perfectly fine at idle and begin misfire the second you put it into gear or under loads. Plugs/coils misfire most when under load. Have you checked them?
if you've changed the spark plug and no difference, then it's time to swap the coil with another cyl. coil and see if the miss goes to the other cylinder, if it does'nt follow to other cylinder, then I would replace that injector !
no, and you were down a litre that wont matter, it sounds like a bad coil boot or coil thats arcing out on a load, i think this car has coils that go onto the plugs and the boots go bad, you can replace the boot on some cars without replacing the whole coil, you may want to tune up the car if its been a while and has over 70,000 miles,also if the engine was misfiring then the computer would pick up the misfire and store a code, this code which can be pulled with a scan tool, or most auto part stores will scan the computer and give you the code the code will tell you which cylinder is misfiring this way if it still misfires after the tuneup then you would need to replace the coil for that cylinder, heres a few diagrams showing the coil and theres one for every cylinder and then the boot which is sold speratly, hope this is helpful,
How do you know it's not a injector ? Could have a burnt transistor or driver in the PCM - engine computer . This transistor or driver supply's a PWM -pulse width modulated ground . No code's shown so probably not that . What is the compression of all the cylinders . How are you checking for codes ? Code reader ? A professional type scan tool that can view mode 6 data would show misfire counter . would know what cylinder is misfiring . Could have a transistor (driver) for coil control that could cause a misfire ,but would be two cylinders missing . Video's on youtube showing how to test a PCM/ECM driver (transistor) How to test computer transistor driver without scan tool