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"misfire codes"

20streetrod06

Full Member
Joined
Oct 7, 2020
Messages
273
Location
Central IL
found a 2003 at a dealership, its too far for me to personally look at just on whim, so i emailed them to learn some more about it.

they just said it has "misfire codes" and needs suspension work. they aren't being anymore specific than that. from the pictures the truck is sitting level, so nothing is crazy broke suspension wise.

but what would be the common culprits for "misfire codes"?

here's a link to its listing
 
What would cause misfire codes let's see

Clogged cat converters
Leaking intake manifold gaskets
Bad ignition parts wires coils spark plugs etc
Head gaskets.

Unless you have mechanical experience, I would pass, it could have several problems. Or plan on replacing the motor.
 
More Misfire reasons:
Bad AFM and ruined lifters and cam.
Fuel injector issue.
LEaking valves.

ANYTHING in the engine could cause misfire....

Cost could be Free to a whole new engine....
BEst to find out what is cause first.
 
alright. thanks guys. that was kind of what i figured, but figured id get the opinions of others.

which being an '03, it wouldnt have AFM correct? even so, that still leaves alot of other variables that it could be, and could be expensive.
 
Get the actual CODES.

Misfire on particular cylinder is easier to diagnose than random misfire and maybe simple to fix.
 
When doing your troubleshooting, consider that these coils rarely go bad.

And almost never all 8 at once.

That's an expensive mistake I see people make, sometimes by just replacing all of the coils without testing.

If you read the error codes and only one cylinder is showing a misfire, concentrate your efforts on that one cylinder first.

Swap that coil to another cylinder and see if the misfire follows the suspect coil, or not.

If the misfire follows that coil, replace just that one coil.

If the misfire stays with that cylinder, focus on that cylinder and leave the coils alone.

When replacing ignition parts, stick with only OEM replacements.

If I was working to find the misfire on that engine, I would certainly look at the intake manifold gaskets.

Those years were known for leaking intake manifold gaskets and those may never have been changed.

For the price of a gasket kit and a few hours of your time, you might just solve the misfire issue.

And having fresh intake manifold gaskets is not a bad thing.

For the intake gaskets, go with Fel-Pro.

Misfires on a 2003 engine is often not as hard to find and fix as on the 2007+ AFM engines.

There is no AFM on the 2003 to worry about.

My bet is on leaky intake gaskets and/or old spark plugs and wires.

That's where I would start and go from there.

Maybe that is all it is.
 
Here is another thought, you are dealing with a Dealer who has all the tools to fix it. If it was an easy fix they would have fixed it and ask for another 1,000 dollars. They choose not to fix it
 
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Here is another thought, you are dealing with a Dealer who has all the tools to fix it. If it was an easy fix they would have fixed it and ask for another 1,000 dollars. They choose not to fix it
^ This. I would be very leery to buy a vehicle from a Dealer that has a check engine light on that they are not willing to investigate or fix.
 
found a 2003 at a dealership, its too far for me to personally look at just on whim, so i emailed them to learn some more about it.

they just said it has "misfire codes" and needs suspension work. they aren't being anymore specific than that. from the pictures the truck is sitting level, so nothing is crazy broke suspension wise.

but what would be the common culprits for "misfire codes"?

here's a link to its listing
I had issues with coil pack #8 causing issues more than 3 times. My mechanic is on the ball and found the issue fairly quickly. Of course, it is the hardest coil pack to get to on the Avalanche. It is at the passengers side firewall on the left side of the engine. I'm told that it overheats that coil pack with the Chevy OEM engine. I replaced my engine at 307k miles with a Jasper that has 340k miles on it now. I haven't had any more issues.
Best of luck to you, hope this helps.
 
I had issues with coil pack #8 causing issues more than 3 times. My mechanic is on the ball and found the issue fairly quickly. Of course, it is the hardest coil pack to get to on the Avalanche. It is at the passengers side firewall on the left side of the engine. I'm told that it overheats that coil pack with the Chevy OEM engine. I replaced my engine at 307k miles with a Jasper that has 340k miles on it now. I haven't had any more issues.
Best of luck to you, hope this helps.
You have 647,000 miles on your vehicle? That has to be a record!
 
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