I did my glow plugs 2 months ago. My problem was a rough,smoky idle for about 20 seconds after start up. Good idea to soak them with PB Blaster or equivilent for a day or two before you decide to remove them. I sprayed mine once a day for about a week before replacement and about an hour before I started. They all came out without a hitch. The only thing I disconnected was the throttle linkage from the firewall to make room for the Gear Wrenchs on #4 & 5 so it took me about an hour and a half. I just didn't want to disturb too much since it is 25 years old. Figured the less I disconnected the better. Turned out none of mine were actually bad. Just used JimmyL's reamer and all the GP holes were carboned up. 2,3 & 5 were particularly bad but since I had the new plugs at $13 each, I installed them. Glow for 5 seconds and it fires up with barely a second on the ignition to a nice smooth idle. Also, the squeaking you may hear when you're removing is most likely going to be the plugs against the carbon built up around the tips so don't fear you're stripping the threads as you're removing them. A little shot of PB once you loosen them will be fine. Good luck...

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Sharing my partner's 2012 Forte 5dr SX til I find my next 123 or 126..
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Do I miss being a service advisor ???