You are here:

Chevrolet Repair/Injector miss fire

Advertisement


Question
hi.. i have a 2004 chevy colorado with 3.5l engine,have fault code p203 and 303 for cylinder #3. i have replace coil pack and all spark plugs and also the fuel injector for #3 cylinder. i have checked the wire harness only from the inj to the back of engine where it plugs into  main harness. i still have engine miss fire and not running good. i have no access for any wire schematics or any way to test the ecu. do you have any ideas or advice that i may have not tryed?? thank you.

Answer
HI JASON, OK WHAT I WOULD DO IN YOUR SHOES IT GET YOURSELF A MARKER LIGHT BULB, #921 GO TO THE PART STORE GET ONE COST YOU ABOUT $1.25 OR REMOVE THE LIGHT BULB FROM YOUR LICENSE PLATE LIGHT HOUSING. THIS SHOULD BE A 194 OR 921 BULB. BEND THE TABS STRAIGHT OUT AND REMOVE THE INJ PLUG HARNESS THAT IS NOT FIRING ON THAT CYLINDER. PUT THE LIGHT BULB WIRES IN EACH SIDE OF THE FUEL INJ HARNESS AND START IT UP..THIS LIGHT SHOULD BE GOING ON AND OFF. THIS IS CALLED A PULSE. THIS COMES FROM THE PCM..IF NO PULSE HERE, EITHER THE PCM OR WIRING HARNESS IS BAD...BUT LETS SAY THERE IS A PULSE AND YOU KNOW FOR SURE YOU HAVE IGNITION [SPARK AT THAT CYLINDER] THE ONLY THING LEFT IS INTERNAL PROBLEMS SUCH A BAD VALVE...IF THIS IS THE CASE GET YOURSELF A COMPRESSION GAUGE AND TEST THAT CYLINDER..SHOULD HAVE ABOUT 150 LBS OR SO + OR- 25 LBS. I DO NOT KNOW HOW YOU HAVE CHECKED THE INJ HARNESS FOR A PULSE ?? LET ME KNOW IF THIS DOES NOT HELP YOU,,GOOD LUCK,TOM..

Chevrolet Repair

All Answers


Answers by Expert:


Ask Experts

Volunteer


TOM SHEETS

Expertise

PLEASE READ ALL OF THIS BEFORE ASKING ANY QUESTIONS. IF THIS CHEVY SECTION IS MAXED OUT.YOU CAN REACH ME IN THE OLDS/BUICK SECTION. Will answer questions from 6:00am to 10:00pm all days [EST][[[ NO DIESEL OR PAINT QUESTIONS]]] will answer all 1965 to present QUESTIONS ON ALL GM'S on mechanics of these cars. Keep in mind i am not there in person i am going on what you are telling me !! PLEASE IF ASKING A QUESTION GIVE ME AS MUCH INFO AS POSSIBLE. THE MORE THE BETTER. SUCH AS YEAR,MAKE,MODEL,ENGINE SIZE. THIS WILL HELP ME HELP YOU. I will not be able to answer all questions because of some situations that i would really need to be there and see things for myself,such as electrical issues. In many cases i would need wiring diagrams. I can also give you an estimate on what the cost would be at our repair shop as an idea to help you. Keep in mind that my answer is ONLY MY ADVICE,ck with your mechanic as well.. >> THANK YOU, TOM..

Experience

I have been a ASE certified master mechanic for over 30 years and certified IN ALL 8 CATEGORIES,[engine repair,engine performance,auto trans,manual trans,clutches,steering and suspension,brakes,electrical systems,heating and air/cond. I am also a state CERTIFIED inspector for over 30 years. I do computer work [pcm]fault codes,pcm flashing,state inspection monitor readiness,repairs on exhaust,fuel service,[injection and carburetor,] charging system problems, running issues,alignments,frame problems,tire balance,struts and of course standard and anti-lock brakes.

Organizations
nys state auto repair industry and ase group.

Publications
N/A

Education/Credentials
high school,4 years of tech school,and many many hours of auto training with many gm classes and aftermarket training classes..

Awards and Honors
ASE MASTER TECH CERTIFIED IN ALL 8 CATEGORIES.NYS INSP LICENSE AND A/C CERTIFIED

Past/Present Clients
MANY CUSTOMERS IN OUR BUSY SHOP.

©2016 About.com. All rights reserved.