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I have a 2006 hummer h3 3.5l on tcc enable begins missfire…

Customer Question
I have a 2006 hummer...
I have a 2006 hummer h3 3.5l
on tcc enable begins missfire in all cylinders, but generally in 4th, only in round 1900-2100 rpm.
MIL blink.
in memory only p0300.
Submitted: 11 months ago.Category: UK Car
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Answered in 1 day by:
9/21/2017
UK Auto Mechanic: Dan, Technician replied 11 months ago
Dan
Dan, Technician
Category: UK Car
Satisfied Customers: 26,040
Experience: Independent Shop Experience, 2 Year Automotive Diploma, & Access to Information Database
Verified

Hello, my name is ***** ***** I'm here to help get your problem solved.

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UK Auto Mechanic: Dan, Technician replied 11 months ago

Has anything been replaced?

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Customer reply replied 11 months ago
valves, springs, converter, valve body, sparks, coils, cam sensors, timing, balancer chain, PCM,
all TSB's for p0300 for L5 engine...
UK Auto Mechanic: Dan, Technician replied 11 months ago

Sounds like you have replaced everything, I'm not sure what else there is to even try. I'll open question up to see if someone else has some ideas, thanks.

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UK Auto Mechanic: Chad Farhat, ASE Certified Technician A6 - Electrical / Electronic systems A7 Heating / Air conditioning systems replied 11 months ago
Chad Farhat
Chad Farhat, ASE Certified Technician A6 - Electrical / Electronic systems A7 Heating / Air conditioning systems
Category: UK Car
Satisfied Customers: 5,783
Experience: Owner at Carolina Auto Service & Sales , 20 years Experience in Foreign & Domestic Vehicles
Verified
Hey how are you
I read the notes and parts replaced .
I have a question , the p0300 is a random multiple misfire, usualy caused by coils,plugs ,fuel,injectors and the most common is Intake manifold vacuum leak from gaskette or intake cracked itself ?
Now have you done a smoke test to check for leaks ?
Do you have scaner that read live data,if u do get me fuel trims reading long term and short term at idle and at operating temp .and I can help you further on it
Also the fuel status : is it open loop when cold and switches to closed loop when it gets warm .
Let's start here and we go from there ,I will try to help you on it best I can
Chad
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Customer reply replied 11 months ago
ok! 300 is random, bat i see in scanner missfire in all cylinders.
in TCC lockup in 1900-2100 rpm i see missfire in all cylinder, but in 4th - several times it's more.
smoke test is ok.
in closed loop status
short - -3%
long - 1%
in open (cold) - in this case are insignificant
UK Auto Mechanic: Chad Farhat, ASE Certified Technician A6 - Electrical / Electronic systems A7 Heating / Air conditioning systems replied 11 months ago
Based on what you said those fuel,trims are correct ,within specs of 5% or -5% ,
That leaves us injectors and fuel,pressuer did you check you know fuel,pressuer specs
In cold open but does it switch to closed when o2 sensor heats up and Ecm switches to them.
Also what are the o2 sensor reading upstream and downstream at idle at operating temp
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Customer reply replied 11 months ago
ok. in this car is alternative fuel system - propane gas equipment - work in the same way.
o2 sensor - swing in correct diapasonю
mysticism.
over 2100 rpm - all OK
UK Auto Mechanic: Chad Farhat, ASE Certified Technician A6 - Electrical / Electronic systems A7 Heating / Air conditioning systems replied 11 months ago

oh , i did not know that ,

i m not sure how that differs from gas ,but it must

if i want to guess , we have clogged injector on number #4 and at 2100 rpm the fuel pressure is rising ?

pull #4 plug is dry or soaked with fuel ?

have we done a compression test on all #4 , are we around the 215 psi

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Customer reply replied 11 months ago
i probary driving without fuse in fuel pump wire. (only in propane), for isolation with injector's trouble - nothing change.
NOT clogged injector
UK Auto Mechanic: Chad Farhat, ASE Certified Technician A6 - Electrical / Electronic systems A7 Heating / Air conditioning systems replied 11 months ago
Ok , that is all I know on it to be honest with you but I can opt out of the question and open it for other expert .
But I agree with you ,since you took fuel pump wire off and still the same ,
Just let me know .Also I want you to read this TSB on p0300
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Customer reply replied 11 months ago
ALL TSB for P0300 are executed.I have AllData & mitchell on demand. :-)
Customer reply replied 11 months ago
I have no more idea. :-(
UK Auto Mechanic: Chad Farhat, ASE Certified Technician A6 - Electrical / Electronic systems A7 Heating / Air conditioning systems replied 11 months ago

yes i m sorry me neither

But I will opt out of the question and open to other expert ,maybe a n expert on the site run into before

sorry again

just do not reply back to me since it will lock question back to me and other expert want see it to assist further

just wait and it will be picked up

good luck to you

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