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Mazda: Mazda 626, fuel injection system, mazda dealer


Question
Hi I own a mazda 626 eclipse 1990 model and when it idles the speed SOMETIMES fluctuates about 100 rpm up and down. This does not happen if you put the A/C on. Is this normal? If not what could be the problem. Also does this car have a "check engine" light. If it does not how can I tell if there is something wrong with the fuel injection.

Answer
Dear Ryan,
Thank you for your question.
I am not familiar with this model, we have not had this one in the UK. I'll proceed onn the assumption that your vehicle identification has a GD in it.

In general terms it is not unusual to have some fluctuation on the RPM. The reason why the AC  makes a difference is because the vehicle has a compensator arrangement, so that when the AC goes on, the idle speed automatically goes up so as to prevent the vehicle stalling.

It is possible that you have a fuel inj. problem but this would not be brought to your attention through the check light.

The fuel injection system can have it's line pressures checked which may reveal any difficulties.

The spark plug colours may tell a story of how the mixture is burning.

Ultimately, ask a Mazda dealer to see if they can adjust the
base idle speed. DO NOT let any unqualified person tamper with the settings as they could do irrepairable damage.

Good luck

Andy