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Ok so far this is what I've done.
1.Replaced Fuel Filter and Fuel pump assembly (used) in September.
2.Replaced Spark plugs(NGK)/Wires(Duralast) in September.
So today I went to replace the Spark plug wires because I thought they went bad. But it did not solve the problem. Car still idles rough and struggles when accelerating. Does this mean i probably need a new coilpack?
The only other thing it could be is a faulty fuel pressure regulator. I'd suspect the coil pack next, but the FPR could be fluctuating as well and not maintaining pressure.
Easy to diagnose bad coil problem. When the car is running rough, unplug one cylinder from one coil pack and see if idle changes. Repeat for other coil pack. One coil pack fires two cylinders so if one bad is, so is the other.
If you are indeed running on two cylinders, you will quickly destroy you catalytic converter from the raw fuel being dumped into it.
What year is the car?
Could be CPS , cam or cank sensor too.
Thanks for the response guys. It is a 1990 miata with a 1.8L from a 94.
dirty or faulty fuel injector.