1994 Toyota 4Runner How to reduce Idle speed 1800 RPM to 80

PHILIP_LAO

MEMBER
1994 TOYOTA 4RUNNER
6 CYL
2WD
AUTOMATIC
273,000 MILES

I have 1994 toyota 4runner 2WD, V6, Auto transmission. I replaced the blown head gaskets on the engine. I double checked timing belt installations position and the distributer installation marks according to the servic manual. The truck starts and runs very strong. Except it idles very high at 1800 rpm and unable to check timing. Currently the distributor is rotated right in the middle of the adjustable range and the throttle is absolutely closed and can't close any more.

What could be causing the engine to run fast?

Is it possible that I have a vaccum leakage into intake manifold? If so what are the possible/common sources?

Would a bad PVC value cause a significant vaccum leakage?

7 Replies

RASMATAZ

MECHANIC
75,992 POSTS

The problem: High idle, is it doing this prior to you replacing the headgasket?

When you put the engine up on its compression stroke/TDC on no.1 piston-did you verify that both valves are closed on it? We move from here

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Sunday, August 23rd, 2009 AT 12:41 AM

PHILIP_LAO

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6 POSTS

I verified the timing belt installation with the marks on the cover/block as well as with the method you suggested, TDC on cylinder 1 with the valves closed (Cams not pushing the valves). Head was serviced and valves are not leaking for sure.

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Sunday, August 23rd, 2009 AT 11:09 AM

RASMATAZ

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Did you jump TE-1 to E-1 when you set the ignition timing?

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/valve stuck in the extended (high idle speed) position/throttle position sensor. Also the throttle plate could be binding in its bore and kinked accelerator cable

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Sunday, August 23rd, 2009 AT 11:36 AM

PHILIP_LAO

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After reading the manual on tune up section I realize there is an air bypass screw to adjust Idle. I was making sure to close the throttle like in old carbs. I learn something new.

I can now adjust the idle and timing both. Yes, I connected TE1 and E1 before checking for timing.

After adjusting the timing according to spec, the engine has LESS power. The timing was quite abit advance before. Any reason this could happen?

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Sunday, August 23rd, 2009 AT 5:38 PM

RASMATAZ

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Once you set the timing the computer has control over it, when you disconnect the jumper on the check connector-it won't be 10deg BTDC

The ABS is hidden under a plastic cap