2008 Equinox 3.4L Cold Start Missfire - TerrainForum.net: GMC Terrain Forum
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post #1 of 5 (permalink) Old 10-31-2017, 09:15 PM Thread Starter
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2008 Equinox 3.4L Cold Start Missfire

A few days ago I noticed on cold starts (seems to be worse the colder it is outside) that my car misfires and the engine light blinks 5 or so times before the car clears up and the light goes away. This happens every-time I start it now for the first time of the day for the last 3 days.

I did buy this vehicle used a couple years ago. I replaced EGR/EGR Tube, AC Delco Plugs and Wires, and have ran some injector cleaner through it over the last 6 months. All of that was just regular maintenance I was doing to it besides the EGR as I was getting some codes from it due the to entire EGR tube being broke in half.

Anyways, so tonight I decided to take it to a shop to get the codes read. It had 9 codes all of them had to do with the EGR valve other then the engine misfire. Which was code P0301. I was assuming the EGR was throwing the codes at the same time due to the engine actually misfiring, however I could be wrong.

Also completely unrelated, however when I accelerate I hear air going through the coolant system. I have googled and have done research, but after owning this vehicle for the last couple years I have realized that it has a very slow coolant leak. Like very slow, but I'm assuming it's enough to let air get back in the system after I bleed it each time. Any idea on where to look?

Any help on it would be greatly appreciated!

Last edited by jlw_4049; 10-31-2017 at 09:17 PM.
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post #2 of 5 (permalink) Old 11-01-2017, 02:31 AM
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Quote:
Originally Posted by jlw_4049 View Post
A few days ago I noticed on cold starts (seems to be worse the colder it is outside) that my car misfires and the engine light blinks 5 or so times before the car clears up and the light goes away. This happens every-time I start it now for the first time of the day for the last 3 days.

I did buy this vehicle used a couple years ago. I replaced EGR/EGR Tube, AC Delco Plugs and Wires, and have ran some injector cleaner through it over the last 6 months. All of that was just regular maintenance I was doing to it besides the EGR as I was getting some codes from it due the to entire EGR tube being broke in half.

Anyways, so tonight I decided to take it to a shop to get the codes read. It had 9 codes all of them had to do with the EGR valve other then the engine misfire. Which was code P0301. I was assuming the EGR was throwing the codes at the same time due to the engine actually misfiring, however I could be wrong.

Also completely unrelated, however when I accelerate I hear air going through the coolant system. I have googled and have done research, but after owning this vehicle for the last couple years I have realized that it has a very slow coolant leak. Like very slow, but I'm assuming it's enough to let air get back in the system after I bleed it each time. Any idea on where to look?

Any help on it would be greatly appreciated!
Hey there,


The misfire can be caused by any number of things. One thing to look for is if it misfires more when the air is moist. If it does, that is a sure sign of possibly a bad coil pack. Something else that can cause it is a possibly damaged plug, or wire. Also, make sure your wires are all plugged into their correct ports.... Also, you mentioned a coolant leak. Check your cylinders for any signs of coolant and you may want a to have a compression check. If none of the above applies, then, the next, less expensive step would be replacing the ECM. If this still does not fix the issue, then the last issue could be the timing chain.


Your EGR quite possibly has carbon build up in it as well from this. Remove it and spray it out with spray carb/throttle body cleaner... Chemtool B-12 usually works best.


As for the coolant leak if the above doesn't apply, there is a notorious plastic heater Y connector that is located off of a tube to the heater core, and also has a connection from the engine, and the reservoir that is known for self-destructing slowly over time. One weird sign is after your engine has been running, and you open the hood, you may hear a drop of coolant hit the manifold on the driver's side of the engine. It will usually be just that connector.


I hope this helps,


Starflare5.
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post #3 of 5 (permalink) Old 11-11-2017, 10:50 AM
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First thing is to write down ALL codes, then clear them. Now drive it and see what comes back. You need to narrow down the problem.

Like, is it a general misfire or always the same cyl.
You can spend days looking for what could cause it instead of what is causing it.
A code reader helps but you need to look at the "live" data while its running to get a more accurate diagnosis.
Dont just start throwing "this might cause it" parts at it till its fixed.
And if you take it to a mechanic that does this, find a new mechanic.
This is what I refer to as a parts replacer, not a mechanic.
Sometimes you have to throw parts at it, but most of the time a proper diagnosis will tell you whats wrong and you can fix it the first time.
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post #4 of 5 (permalink) Old 11-11-2017, 11:26 AM
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Isn't the 3.4L engine notorious for bad intake manifolds which then cause coolant leaks like you are describing?

2018 Equinox LT1 1.5 L 4 cyl, AWD, S/R Cajun Red Tintcoat/Black

2010 Equinox LTZ 2.4 L 4 cyl, FWD, S/R Cardinal Red/Black
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post #5 of 5 (permalink) Old 11-11-2017, 12:08 PM
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This sounds very familiar to me. Happened with my '97 Taurus - and with the same cylinder. I would get the flashing CEL with the same P0301. I would change the plug and it would be fine for a while ... a long while ... like a year.

But the car was losing coolant, and I knew it was going through the engine.

You've very likely got a lower intake gasket, and possibly even a head gasket leak. The failure is around cylinder #1 which is fouling that plug. The gurgling sound you're hearing is due to air in the system. Maybe you filled it and didn't purge out the air (if it's not self-purging), or air is getting sucked in?

You probably have some white smoke coming out your tailpipe, or can even smell a whiff of coolant around the hood area after turning off the car?

2011 Equinox 1LT (new Jan 2011): Summit White / 3.0 L V6 / FWD / Pioneer Stereo / 18" Wheels / 138.2k miles [05-NOV-2019]

2002 Impala 1LT (new Jun 2002): Summit White / 3.4 L V6 / FWD / Cassette-CD Combo /225.5k miles [05-NOV-2019]
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