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For the last couple of weeks, every time I stop at a stop light or stop sign, my Chevy Trailblazer idles very rough. It feels like it's going to stall (does the little shudder thing that cars do right before they stall), but it hasn't ever stalled, yet. I was hoping it was bad gas, so I let the gas run down and filled it up with premium and put in some STP fuel cleaner, but that didn't help. I took it to get it hooked up to the computer, but no lights were on, so there were no comments. Well, this week, the check engine light came on, so I took it back and they hooked it up to the computer again. This time it listed 4 things, but the most likely thing was spark plugs. Is that something that could cause the problem I'm having? On my vehicle, are the spark plugs easily accessible (that I might be able to have my boyfriend change them?) or does it need to go in the shop? If I take it to a shop, should I take it to the dealer, or can I take it anywhere? About how much should they charge me for replacing spark plugs? Would I only need to replace one, or should I replace them all? Thanks! Stacey

Answers from the Automotive Experts

Helaine Kurot, Owner/Technician at 360 Automotive Lets start with fuel. This is most likely not the cause of your drivabliiy complaint. Taking a fuel sample is not a bad idea though, just to be sure. If your vehicle does not call for a higher octane fuel, using premium over regular will not help you. It may even cause other driveablity issues, although usually they go unnoticed. Gasoline is rated in octane. The other terms used (i.e. premium, silver, etc) are just marketing tactics. The higher the octane, the longer the burn time. If your car is not set up for running on a higher octane fuel, you are wasting money. The check engine light coming on may be a good thing. It will give the auto technician a direction in which to start although there is also a possiblity that the codes pulled are not related to your drivability concern. Your best bet is to take the car to a reputable repair shop and have them do properly diagnoise the vehicle. Hooking the car up to a computer and pulling codes is not the same has having it diagnosed. Without having a proper diagnosis done, you are just throwing parts at the car. In the long run this will cost more than having a properly trained technican diagnois the cause of your concern. You do not need to go to the dealer for this, but you do need to find a good repair facility. If you or your boyfriend is mechanically inclined, you probably could change the spark plugs yourself. Change all of them at the same time. Use AC Delco plugs. Most parts stores will sell them, if not you can pick them up from the dealer.

Barb Petrey, President - DBK Enterprises Inc at Jiffy Lube all spark plugs should be replaced at the same time. Ideally, you should change the spark plugs every 60,000 miles. Generally they are not hard to replace but make sure they are gapped correctly. Check your air filter at the same time. If your boyfriend does not do the job, you do not have to go to the dealer, go to a mechanic.

Amy Mattinat, Owner and Author at Auto Craftsmen Ltd Hi Stacey, I wish you had listed the 4 codes listed when they shop scanned your Trailblazer's computer. With 4 different codes, there could be multiple things going wrong at the same time. If you do change the spark plugs you need to do all of them. I recommend you take it to a qualified auto repair shop and have them diagnose all the problems.

Amanda J. Pierce, MBA Stacey, to answer your question, you should replace all plugs at once in conjunction with spark plug wires. You can visit the dealership if you choose or have a recommendation of a local shop a friend has used. Labor rates are based upon shop so call around for quotes for a benchmark price in your area.

Colleen McGee, Driving Instructor at Americas Driving School Hi Stacey yes spark plugs can cause the shuddering you describe. They should be easy to change on your Trailblazer and yes you should change them all. Any mechanic could do the job, a dealer would probably be more costly. The cost could be between $100-300. If your boyfriend could do it it would save you quite a bit. good luck!

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