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+--- Thread: My Grand Cherokee is idling rough – could it be spark plugs? (/showthread.php?tid=1699)
My Grand Cherokee is idling rough – could it be spark plugs? - adamzampa - 07-21-2026
I've noticed my 2016 Grand Cherokee has been idling a bit rough lately, and there's a slight hesitation when I accelerate from a standstill that wasn't there before. Fuel economy has also taken a noticeable hit, which is making me think it might be time for a tune-up, possibly new spark plugs. I've read that the Pentastar engines can be sensitive to worn plugs, and replacing them can sometimes smooth out the idle and improve throttle response quite a bit. I'm based in Abu Dhabi and I'm looking for a workshop that can do a proper replacement with genuine plugs, because I've heard that using cheaper alternatives can cause misfires or even damage the ignition coils over time. I found a place that offers Leading Jeep Spark Plug Installation in Abu Dhabi, but I'm curious if anyone here has had a good experience with them or can recommend another reliable specialist in the area. I'm also wondering if they typically check the ignition coils and wires while they're at it, because I'd rather get everything sorted in one go. Any advice would be a massive help.
RE: My Grand Cherokee is idling rough – could it be spark plugs? - hertawintle - 10-09-2026
Rough idle, hesitation and a drop in mpg fit worn plugs, but they fit a failing coil just as well. On the 3.6 Pentastar the plugs sit deep under the coils, so it’s worth having them pull the codes first and check for a misfire on a specific cylinder. That tells you if it’s plugs or a coil.
RE: My Grand Cherokee is idling rough – could it be spark plugs? - hertrudewiseman - 10-09-2026
Did the plugs on my 2015 Cherokee at around 100k km and the idle smoothed out straight away. The old ones were badly gapped. The shop also found one tired coil and replaced it in the same visit, so ask them upfront whether they’ll test the coils instead of just swapping plugs.
RE: My Grand Cherokee is idling rough – could it be spark plugs? - hesperwish - 10-09-2026
Not convinced it’s automatically plugs. Hesitation from a standstill can also be a dirty throttle body, a clogged air filter or a sensor drifting. Plugs are cheap to try, but I’d get a scan with fuel trims first so you’re not paying for a tune-up that doesn’t fix it.
RE: My Grand Cherokee is idling rough – could it be spark plugs? - hesterwishart - 10-09-2026
Genuine or OEM-spec plugs matter on these engines, the Pentastar is picky about heat range and gap. Ask for the brand and part number on the invoice and check it against the manual. Also ask if they use a torque wrench, since overtightening in aluminium heads causes expensive thread damage.
RE: My Grand Cherokee is idling rough – could it be spark plugs? - hettawithers - 10-09-2026
How many km on the Grand Cherokee, and have the plugs ever been changed? Does the rough idle show up cold, hot, or both? And is the check engine light on or flashing? That would help people here tell you whether it’s plugs or something else.
RE: My Grand Cherokee is idling rough – could it be spark plugs? - youngdragoon - 10-18-2026
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