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Q: Truck is missing only when it is in gear

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A couple weeks ago my truck started randomly missing while driving then gradually got worse till it was constantly missing but only while in gear.It runs fine while in park.I replaced plugs,wires,and coil packs about a year ago.Yesterday I changed the fuel filter,cleaned the MAF sensor and checked all vacuum lines for a leak and it is still doing the same thing.The check engine light is not on or flashing and it isn't throwing any codes on a scanner.What am I missing here?I don't understand what else could cause it to do this.

My car has 161000 miles.
My car has an automatic transmission.

Hi there, thanks for writing in.

If this problem only happens when you’re in gear and accelerating, its very possible that it could have a transmission problem that causing a hesitation. I have seen issues like this before. It’s also very possible for the MAF sensor to cause a rough running condition without throwing a fault, or it could have a clogged fuel filter causing low fuel pressure. A clogged or sticking injector wouldn’t set a fault, but can cause a rough running condition as well. There could be a problem with a knock sensor or with the ignition timing. The best place to start would be checking if it’s a transmission problem or an engine problem. If it ends up being an engine problem, start by checking the fuel pressure and ignition timing. If you want to have this issue professionally diagnosed, you can contact a qualified independent technician through YourMechanic.

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