1990 Mazda 626 idelling

RN40492

MEMBER
1990 MAZDA 626
4 CYL
FWD
AUTOMATIC
132,000 MILES

A month ago my mazda was giving a rough idle when comes to lights and when on drive. I was told to change the throttle body which I did but now what happens is when I start the engine, the rev is so high. It does not go down.

i also changed the hose which goes from the air filter box to the throttle body.

The rev is high and after some time it starts to go up and down.

I have not driven it since then.

I also put my old throtle body back since the replcement did not help.

What else I can do to fix this.

1 Reply

RASMATAZ

MECHANIC
75,992 POSTS

Too fast an idle speed. If an engine without computerized idle speed control is idling too fast and refuses to come down to a normal idle speed despite your best efforts to back off the carburetor idle speed screw or air bypass adjustment screw (fuel injection), air is getting past the throttle somewhere. Common leak paths include the carburetor and throttle body gaskets, carburetor insulator spacers, intake manifold gaskets, and of course, any of the engine's vacuum fittings, hoses and accessories. It is even possible that leaky O-rings around the fuel injectors are allowing air to leak past the seals. Another overlooked item can be a worn throttle shaft and a defective idle speed speed control motor stuck in the extended (high idle speed) position