Today i took my car to get smogged, and I failed. The guy says that my car idles with too high of rpms. It idles at around 1300-1500 rpms. I look at all the stuff that it says the test checked, and it says that the vaccum hoses to the switches and such passed, but the ignition timing failed. The last sentence in my test says "This vehicle failed the ignition timing check due to engine RPM being out of tolerance." My car is a 1990 Mazda RX7 GTU manual. Its bone stock. Any help would be greatly appreciated.

 

At idle the timing should be Lead 5 and Trail 10 ATDC.

Idle is at approx 750 rpms.

Anytime the rpms get over 1100 rpm, the ECU automatically advances the timing waaaaay over the figures above. Therefore you didn't meet the requirements of the smog place.

Lower the rpms, and the timing will fall into place. UNLESS someone has monkeyed with the cas and then it will still be off.

Figure out why your rpms are too high and you solve your problem.

 

The idle speed is too high. It should be around 750 RPM. Vacuum leaks are usually the cause of high idle if the idle speed screw adjustments haven't been changed.. The higher rpm will cause the electronics to advance your timing. You can't adjust the timing with high RPM. Do you know the timing procedure? Yor first step would be to find the cause of the high idle. There is a Thermal wax located in the body of the throttle body. This device controls the cold idle speed. When cold the wax piston pushes agains a cam that opens the throttle plate causing fast idle (like 1500 RPM). This device fails frequently, but usuall in the warm (recessed) position. It is virtually impossible see or check without removing the throttle body. However, it is worth a look if you can't find a vacuum leak. There are also small vacuum check valves in some vacuum hoses. These devices either delay vacuum, or pass vacuum in one direction. They are an in-line device, plastic, and color coded to indicate their function. These frequently fail. Good luck. RX7MAVEN