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Christina Baker

Christ ... 11/15/2017

2000 Jeep Grand Cherokee Laredo 6 Cyl 4.00L


Trying to figure out why it loses power when slowing down from highway speeds

My son's truck loses pressure when getting off of the highway the check engine light comes on and it starts driving really slow almost like it's going to stall. when you turn the car off and let it sit for a while it usually runs fine again after that. I've read that it could be fuel filter spark plugs ignition coils I just don't know where I should start the original codes that I got off it said cylinder 3 and 6 misfire. Anybody who's had this problem help would be greatly appreciated

2 Answers


Jimm 11/15/2017

A code P0303/0306 may mean that one or more of the following has happened:

Faulty spark plug or wire
Faulty coil (pack)
Faulty oxygen sensor(s)
Faulty fuel injector
Burned exhaust valve
Faulty catalytic converter(s)
Running out of fuel
Poor compression
Defective computer

If there are no symptoms, the simplest thing to do is to reset the code and see if it comes back.

If there are symptoms such as the engine is stumbling or hesitating, check all wiring and connectors that lead to the cylinders (i.e. spark plugs). Depending on how long the ignition components have been in the car, it may be a good idea to replace them as part of your regular maintenance schedule. I would suggest spark plugs, spark plug wires, distributor cap, and rotor (if applicable). Otherwise, check the coils (a.k.a. coil packs). In some cases, the catalytic converter has gone bad. If you smell rotten eggs in the exhaust, your cat converter needs to be replaced. I've also heard in other cases the problems were faulty fuel injectors.


Samuel 11/15/2017

Do you mean it loses oil pressure. Why did you say pressure? If not Jimm has this covered. Notice how fuel filter is not in his response. Because it is not that.


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