Rough idling and engine misfire?

KAOMA

MEMBER
2002 MAZDA 6
2.0L
4 CYL
2WD
AUTOMATIC
254,709 MILES

Hi All,

For the past 2 years, I have had a rough idle and engine misfire. The cars always has a rough idle when idling, it gets worse when I engage the gear (drive or reverse), and when I turn on the A/C, when I press the gas pedal to raise the revs the rough idle disappears and runs smooth with high revs, and drives just fine when driving in high way or normal driving, when I stop at a red right it idles rough and at times can even switch off. The other problem is engine misfire, this does not happen all the times, but happens sometimes, basically you can have the engine misfire today as you start it up or even stop at a stop sign or red right, then the engine can run without misfiring for days then misfired again.

The things I have changed, throttle body, spark plugs, fuel pump and fuel filter, fuel injectors, coil pack, high tension cables, EGR valve, battery, Alternator, MAF sensor, Oxygen sensor, coolant temperature sensor, A/C compressor, Steering pump. I have tried disconnecting the battery, then reconnecting it and leaving the vehicle idling for 30 minutes, then turning on accessories and leaving it running for another 30 minutes, but this has not helped at all.

Please, what really could be the problem, I am really tired of spending money on the repairs to the point I just parking it. It is an LF engine.

2 Replies

KEN L

MASTER CERTIFIED MECHANIC
42,942 POSTS

Hello,

I will help you fix the problem; can I ask if the check engine light is on? Also, I have seen a bad fuel injector cause this problem. Here is a guide to help you run the codes and we should do a compression test to make sure the engine is in good shape.

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

and

https://www.2carpros.com/articles/how-to-test-engine-compression

When you remove the spark plugs look for the one that is a different color than the rest, this will be the cylinder having an issue. If you upload a short video of the engine cranking over, I can tell if the engine is hurt or not. Please go over these guides and get back to us.