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Tims Auto Repair
Tims Auto Repair, GMC Mechanic
Category: GMC
Satisfied Customers: 15474
Experience:  have owned a repair shop for 25 years
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I have a 2003 Sierra denali Quadrasteer pick up. Ran great

Customer Question

I have a 2003 Sierra denali Quadrasteer pick up. Ran great and had bad tranny. 165k miles. Just had tranny rebuilt last week, few days passed only put about 300 miles on it. Stepped on the gas to merge on the highway and check engine light started flashing. Pulled over it stayed flashing. Shut it down and waited like 10 minutes. Started right back up and ran and drove fine. But everytime I step on it or accelerate a little on the heavy side it will flash the check engine light. Brought it to OReilly and code scanned it. Bad o2 sensors. Had them all replaced and still having the e sane issues. I'm completely stuck. Also had brand new MAF sensor put in.
JA: What happens when you step on the gas? Do you notice a rough idle?
Customer: Slight rough idle, everytime I get on the gas check engine will flash alot, sounds bad, not wanna accelerate well at all, and will get very bad MPG.
JA: What is the model of your '03 GM?
Customer: Sierra pick up, with Quadrasteer, and 6.0l engine with a rebuilt 4l65e transmission with less then 400 miles on it
JA: Are you hoping to fix this yourself? What have you tried so far?
Customer: Replaced all o2 sensors in exhaust, MAF sensor, checked all connections and, good fuel pressure, I have a fuel pressure gauge installed to monitor it inside my truck
JA: Anything else you think the mechanic should know?
Customer: Had the PCM/ computer in the truck flashed to all factory settings
JA: OK. Got it. I'm sending you to a secure page on JustAnswer so you can place the $5 fully-refundable deposit now. While you're filling out that form, I'll tell the GM Mechanic about your situation and then connect you two.
Submitted: 4 months ago.
Category: GMC
Expert:  Tims Auto Repair replied 4 months ago.

Hi, My name is ***** ***** for the delay.

I will do my best to assist you.

Expert:  Tims Auto Repair replied 4 months ago.

most times when the engine light flashes like this,it indicates a bad or damaged catalyst converter

Expert:  Tims Auto Repair replied 4 months ago.

also,most times will store a p0300 miss fire code

Customer: replied 4 months ago.
Yep I have the p0300 code
Expert:  Tims Auto Repair replied 4 months ago.

ok..

have you tuned it up?new plugs and wires?

Customer: replied 4 months ago.
New plugs, wires, MAF sensor, all new o2 sensors
Expert:  Tims Auto Repair replied 4 months ago.

ok,,i would think you need a new catalyst converter

Customer: replied 4 months ago.
Ok
Expert:  Tims Auto Repair replied 4 months ago.

most muffler shops can do a half way decent test on these

Customer: replied 4 months ago.
I plan to have the cats test. If they check out fine what else would cause it?
Expert:  Tims Auto Repair replied 4 months ago.

i would think you have a bad one

Expert:  Tims Auto Repair replied 4 months ago.

there isnt allot that will cause this on this truck,,other than the tune up,the catalyst and rarely the crank sensor

Expert:  Tims Auto Repair replied 4 months ago.

stand by,,i will give you some tests/checks for the 300 code

Customer: replied 4 months ago.
It has a studder when accelerating at all times. U can hear it
Customer: replied 4 months ago.
Sounds good
Expert:  Tims Auto Repair replied 4 months ago.

i would think it is a clogged catlyst causing too much back pressure

Expert:  Tims Auto Repair replied 4 months ago.

PLEASE COPY AND PASTE the link below to your browser, I have uploaded more info on this there please copy and paste the link below to your main browser[INTERNET EXPLORER or FIREFOX]

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https://www.dropbox.com/s/v1dsfig6zchp009/0718-denali-P0300.doc?dl=0

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if the link doesn’t work that way, try it this way

thanks

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www.dropbox.com/s/v1dsfig6zchp009/0718-denali-P0300.doc?dl=0

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