Why is my car misfiring and stalling after changing spark plugs?
Replacing spark plugs and ignition wires can leave a car running roughly, dropping to a very low idle and dying unless the choke is on. This happens when the underlying cause of the misfire wasn't fixed by the new parts, preventing the engine from running smoothly on its own.
What people tried
Every workaround mentioned in the threads below. We haven’t tested any of them — and nobody here is claiming they worked.
- 1Using the choke to keep the engine running
- 2Removing and reseating HT leads
- 3Reinstalling old plugs and leads
- 4Replacing ignition coils, spark plugs, and fuel injectors
- 5Checking engine compression
In their words
Unedited, grouped by where they were said, most upvoted first within each place, each linked to the thread it came from.
“I recently changed the spark plug/HT leads... and basically the car is running like a dog.”source ↗
“It runs ok with the choke on, but if I push the choke in it starts to misfiring badly and with the choke off basically drops to ~400rpm idle and then dies”source ↗
“Replacing these item did not fix the issue.”source ↗
“After replacing the fuel injector, the P0301 code has disappeared, but the engine is still running roughly and feels the same as it did before.”source ↗
“Any suggestions on what I should test next would be greatly appreciated.”source ↗
Where this came up
People with this problem also raised
- 16Why are my oxygen sensor readings going crazy during a misfire?
- 3What to do if you cross threaded a spark plug
- 14Engine misfires and RPM surging when driving uphill
- 9Why does my car engine cut out after driving for a while?
- 3Why do ignition coils keep failing one after another?
- 2Cylinder misfire and white smoke from exhaust