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Misfiring... P303 code I believe... very rough. Started

Misfiring... P303 code I...

Misfiring... P303 code I believe... very rough. Started after I lost heat and coolant disappeared. I've been guessing head gasket, so I added more coolant + 2x types of head gasket sealant/.repair stuff, but no luck so far. Removed thermostate to take it out of the equasion, better flow. I think the coolant is still going down. Misfiring often. Loss of power. Some bubbles noticed in rad when running, oil looks clean but overfilled (my fault a while back).

Mechanic's Assistant: Have you seen the misfire code before? Has the car been stalling?

It stalled a few times back when it first began, I'm guessing it was overheated. Lately I watch the coolant level and it's been better, no stalls. The code had been repeating, I also got misfire codes on other cylinders, I forget which - it's been a few days.

Mechanic's Assistant: What is the make/model/year of your car?

2003 Buick Regal LS (non-supercharged)

Mechanic's Assistant: Are you fixing your Regal yourself? What have you tried so far?

I told you... that's about it.

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Answered in 4 minutes by:
3/17/2018
Roy
Roy, import/domestic specialest
Category: Car
Satisfied Customers: 7,747
Experience: ASE master tech for 40 years
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hello, my name is ***** ***** I will be glad to assist you. please allow me a couple of minutes to gather some basic info.

Roy

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Customer reply replied 4 months ago
Sure

ok, It does sound like a head gasket. the way to confirm is to have a leak down test done on the cylinder. that is when you remove the plug, inject air into the cylinder and watch for movement in the cooling system.

it sounds like it overheated and thats what started the issue.

do you have availability to shop air and the tool?? if you do not have it, you can rent it at a parts store.

Roy

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Customer reply replied 4 months ago
I have access to a small compressor. Perhaps I can rig something up.

if you have a compression tester, you can remove the valve in the end and use that as an adapter for the test

Roy

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Customer reply replied 4 months ago
Oh I used to, lost it. I can get one cheap. Like, cylinder compression tester right? I can do that. Though, if it's the head gasket, I'm at a loss as to what to do next... try sealants again
or pay for replacement? :(

sealants never work as you already know. all they do is clog up the cooling system and have to be flushed out of the system.

if it is head gasket, the head will need to be removed and inspected. it would be good to replace both at the same time.

Roy

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Customer reply replied 4 months ago
Thanks, it's good to hear that about the sealants. Looks like I have my answer.

your welcome

Please take a moment and rate my service 3 stars or better. that is the only way the site will pay me for my efforts.

Roy

Roy
Roy, import/domestic specialest
Category: Car
Satisfied Customers: 7,747
Experience: ASE master tech for 40 years
Verified
Roy and 87 other Car Specialists are ready to help you
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thank you

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Customer reply replied 4 months ago
Thank you. Have a nice day.

your welcome

you as well

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