Mazda 626 Update

On the day of the class, the idle problem improved all by itself. The car no longer stumbled while stopped at a traffic light. Also when I put the car into Park, the engine did not always stall out.

The instructor said that the ECU may have needed several ignition cycles to relearn its "operating parameters" for the specific car. When I disconnected and reconnected the battery, the ECU probably reseted itself and used factory defaults. Since the car is old, the factory settings could have lead to rough idle characteristics.


MAF sensor

I took out the MAF sensor and it had some carbon deposits on the front side. I didn't clean it because the instructor said MAF sensors are very touchy and sometimes cleaning it will make the probably worse.

IAC valve

The IAC valve is actually a stepper motor controlling a valve which bypasses the throttle plot. The computer adjusts the valve opening to vary the idle speed. The idle speed is increased when the engine is cold, when the A/C is on, when there is a load on the alternator, etc..I measured the IAC valve motor resistance - 9 ohms, which is within spec.

Distributor cap

There was some carbon around the contacts, but no shorts.

Spark plug wires

Measured the spark plug wire resistance
#1, 24", 7.03K
#2, 21", 5K
#3, 18", 6.2K
#4, 15", 4.08K

All wires are about 3K less than spec (16K/40"). Is this bad?

Ignition Coil

Primary side resistance was too low to measure with my DMM. I was unable to get a secondary side resistance measurement. The secondary output post is coated with a white dusty film. I cleaned it up with some sand paper.


Driver side inner CV joint

The grease leak is coming from the seam between the boot and metal shaft. I'll take a pic next week.