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cold start misfire


rockfangd

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Update 10/3/13

I performed the test again and same results.

2 days ago I pulled the lower radiator hose and added 6 supplement tabs, ran til heated up and drove it.

Shockingly yesterday morning it had no misfire on startup, all day no problems, same today. Scantool shown no misfires on any cylinders. I dont really want to get my hopes up yet but I can for sure it is running without any problems.

I completely realize this good news may be temporary but it only cost me a couple bucks to try. This morning I went about 120 miles with speeds mainly around 80. hottest coolant temp got was 201.

I am happy even if this is temporary. I still have a hunch that there was a porous leak on the intake side of the rear head. Which explains why I dont seem to be getting exhaust in the coolant or temp spikes.

If it changes I will update this

GM FAN FOREVER

Nice, clean, luxury= fine automobile

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If coolant tabs solve this one, it will be a first for me. Your idea of a porosity problem in the head would explain your problems, though. I don't know enough about the head to know whether there are thin spots in the casting between the water jacket and the intake ports, but there are thick areas in where the ports go to the valve seats.

Occam's Razor: The simplest possible explanation of a phenomenon is the most likely correct one.

CTS-V_LateralGs_6-2018_tiny.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

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lol. Like I said it may not be permanent but it is definately working at this time. It is nice to be able to start the car and have it not misfire

GM FAN FOREVER

Nice, clean, luxury= fine automobile

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I remember that. The thing is though, I dont know for sure but I feel mine is not pulled head bolts. If I had any issues with that I think it would have gotten much worse. As hard as I drive my Deville I would imagine any problem would show.

GM FAN FOREVER

Nice, clean, luxury= fine automobile

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OK, can we agree that coolant was getting into the cylinder and thus causing the misfire?

If so, then the coolant leak must be somewhere else, and not at the top (where the headgasket is).

So where is the most likely place for this leak to be? At the bottom of the cylinder liner? I don't think so. Mid cylinder? Not too likely either.

In the intake/exhaust passage? Remember, it can (could) be forced into the cylinder during periods where the engine was off, but the cooling system had pressure.

So it must be a continuously low pressure area while the engine is running, (under vacuum) but can be pressurized (by coolant) when the engine is shut off.

Just trying to understand this fix, and how long it might last. At this point I'm leaning toward intake manifold area, where coolant is present.

Any ideas?

Never underestimate the amount of a persons greed.

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It is definately coolant related. I dont know from where it is leaking internally but it must be minor because it doesnt use much coolant., just enough to be burnt off on a cold startup. Even I cannot know how long it will last because I dont believe in miracles, at least not permanent miracles.

GM FAN FOREVER

Nice, clean, luxury= fine automobile

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  • 1 month later...

Just wanted to update this.

Been completely misfire free over 1000 miles so far. driven daily like always. No codes or misfires in history.

Had performed combustion test twice again and passed both times.

I am so happy I finally figured this one out as it was really starting to bug me. But with over 200k I cant complain at all. Car is by far a blast to drive

GM FAN FOREVER

Nice, clean, luxury= fine automobile

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Just wanted to update this.

Been completely misfire free over 1000 miles so far. driven daily like always. No codes or misfires in history.

Had performed combustion test twice again and passed both times.

I am so happy I finally figured this one out as it was really starting to bug me. But with over 200k I cant complain at all. Car is by far a blast to drive

I am glad it is still running well and hope it continues to do so... :hatsoff:

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Congratulations on getting it all squared away, and ruling out head leakage.

CTS-V_LateralGs_6-2018_tiny.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

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  • 2 years later...

Bump. This thread is old, just bumped for reference to another thread.

I retired this vehicle when the headgasket blew, not sure which one but it was major. Went out one day and it went from fine to severely hot quick. Was not worth repairing due to the rust.

GM FAN FOREVER

Nice, clean, luxury= fine automobile

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