Q: My car is running rough after changing the spark plugs and wires.

asked by on October 24, 2016

Had plugs,wires, cap, rotor, and coil replaced.I made sure firing order was correct and is still running rough.I also changed the fuel filter and treated tanks for contamination.
My car has a manual transmission.

Engine is misfiring Inspection $79.99 - $89.99 Get a Quote
Car idle is rough Inspection $79.99 - $89.99 Get a Quote

Hey there, the first thing to check are any trouble codes, even though this is pre-OBD II (Ford MCU or EEC-Iv engine management systems), there are inexpensive code readers for these engines, or your local parts store can read the codes. This should help determine if the problem is ignition misfire (distributor pick-up, ignition module possibly), or fuel (low fuel pressure, dirty injectors, dirty/clogged idle air control valve, dirty throttle body possibly). Leaks in the air intake can also get you - loose or split hoses, EGR valve not closing completely.

I would recommend having a rough idle inspection completed by a mobile, professional mechanic, such as one from YourMechanic, to diagnose this problem, get an accurate assessment of damage and cost estimate for repairs.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

What others are asking

My ford f 150 want turn over changed battery

Hello. There may be one of several issues wrong. When having starting and running issues, always verify that the alternator and battery are working perfectly first. Make sure the battery cables and grounds are clean, dry, and tight. From there,...

Difficult to control in wind and veers above 60 mph

Hello there. This sounds like a more unusual situation. Ford uses the rollover stability control system as an additional safety feature to help prevent rollovers. A bit of body movement in normal wind speeds would not be abnormal. It should...

Car won't start up.

It sounds like your car cranks but isn's starting, if that's the case it's missing one of the three requirements for combustion; compression, fuel, ignition. If, while cranking, the car sounds like it always has and not much faster than...

Key stuck in ignition of a 1988 Chevrolet Camaro

If this is an automatic you can try wiggling the shifter while trying to turn the keys, there is a rod that actuates a lock in the lock cylinder unless its in park. If that doesn't help the lock is...

Radiator issue with my car.

Generally a radiator is not going to cause a car not to start - it is only a heat exchanger for the engine coolant. I think your problem would be more drivability in the fuel (fuel pump injectors fuel lines)...

it has a misfire when at slow speed

An ignition system problem is one of the most common reasons for an engine to misfire. As the spark plugs, ignition cables, distributor cap and rotor, and ignition coil wear over time, their ability to transfer the needed spark to...

I want to replace the entire rear differential on my 93 f150 - not take it apart, just replace the entire differential assembly.

Replacing the differential as a complete assembly is a routine, indeed mundane, repair and so it is possible and quite practical. Insofar as cost effectiveness, the answer depends on exactly what is wrong with your existing differential, if anything. If...

No start

You need to check for battery voltage on the red wire to the coil with the key in the on position and then check the same wire when you go to the crank position. If either one is not as...

Ran out of gas put gas in it but not getting to carburetor maybe it's the fuel filter

You should first try to replace the fuel filter and then with fuel line disconnected test to see if the fuel pump is pumping close to 5 psi of fuel pressure and is pumping fuel. When the vehicle ran out...

Related articles

Symptoms of a Bad or Failing Starter
Common signs include the engine not turning over, starter engaging but not spinning the motor, and grinding noises or smoke when starting the motor.
The Best Used Cars to Buy If You're Towing a Boat
If If you’re towing a boat, the vehicle that you buy is largely going to depend on the size and weight of your boat plus trailer. Most cars, realistically, aren’t cut out for the job. We recommend a pickup truck...
How Often Should Spark Plugs Be Replaced?
While your engine runs on gasoline, it also requires electricity. It’s needed to operate most of your accessories, but is also required to...