Car Struggles To Get Over 10 MPH

Question:
After i drive my car for 30+ minutes and come to a stop, when i try to go it struggles to get to 10 mph and service light comes on saying cylinders 5-6 missfires. I've changed fuel pump twice, all the spark plugs once, spark plug cables once, fuel filter at least 5 times but the problem still there. No auto shops around my area has been able to diagnose what is the cause of this problem. I dont know if it relevent but the steering wheel shakes a good bit while driving. I got my tires rotated and balanced but that did not help.

Answer:
First off I don't know why you changed the fuel pump because that cannot cause engine misfires on one or two cylinders. A bad fuel pump with low-pressure would cause hard starting, poor acceleration, misfires on all cylinders and other problems.

Read More Below Or See These Related Articles:


 

If you changed the fuel pump because it kept going bad, and the fuel filter a few times, it's very possible that there is dirt and debris in the bottom of the gas tank. This will cause a fuel pump to fail, fuel filter to get plugged up and also plug a fuel injectors.

Plugged fuel injectors can cause engine misfires. You would need to do what is called a fuel injector balance test and compare the results of number five and number six cylinders with the other cylinders that are running fine. If you find those two have a low-pressure drop compared to the others, the injectors are either plugged or they are bad and need to be replaced. If there plugged a good cleaning service my help.

If the spark plugs and spark plug wires have been replaced you also need to check the ignition coils. Again, this depends on what kind of car you are talking about. If the car has good spark and good fuel injectors, the next thing is to check for it mechanical failure in the engine. This is unlikely because the car only acts up after driving for a while.

The last thing the check would be for a plugged catalytic converter. A plugged catalytic converter usually acts up when it gets hot, so that might explain why it doesn't happen till you have been driving for 30 min. These will cause very bad acceleration, no power and can also cause cylinder misfires. Depending on the car, it can also cause EGR valve codes with a check engine light.


Help Keep Us Free-
Tip / Donation To the Mechanics


Q and A Main


How Things Work


Electrical