90 Sidekick high idle on cold start

FGROH

MEMBER
1990 SUZUKI

90 Sidekick 1590cc with new valve job at 125000 miles. On cold start, idles at 2500+ for several minutes then gradually idles down to about 1000 (acceptable) after about 5 minutes. The manifold vacuum operated dashpot has been adjusted to not cause high idle, IAC bench tested & cleaned, no vacuum leaks (pulls 17-19" at warm idle), and 5v reference volts at connector.

I don't have the shop manual, nor know how to pull codes on this car.

There are 2 electric/vacuum switches (red-manifold; blue-ported) mounted on front side of valve cover. Appears ported vacuum operates the EGR, whereas manifold vacuum is the dashpot on side of Throttle Body (decelleration?)

Confirm I re-connected the vacuum lines correctly and explain function if I have it wrong.

I don't believe the IAC is adjustable, so I can't determine cause of abnormally high cold idle.

I'm new to you, but am happy to make a donation if you can help me solve this issue without buying the shop manual.

1 Reply

DAVE H

MECHANIC
13,383 POSTS

Idle Speed Control (ISC) Solenoid
An air passage by-passing the throttle valve is provided to route filtered air directly into intake manifold. The flow of air through this passage is regulated by ECM energized ISC solenoid valve. Solenoid is located on side of throttle body.
Air is allowed to pass through ISC solenoid valve when it is energized. Solenoid is energized whenever idle speed drops to less than desired RPM due to engine load (i.E. Electrical, A/C, P/S, auto. Trans. In Drive, etc.). ISC solenoid valve is also energized each time engine is started, or during periods of deceleration (to compensate for rich mixtures caused by a fully closed throttle). Duration of ISC solenoid valve operation is dependent on coolant temperature.
Throttle Opener Control System
When vehicle is first started, ECM energizes throttle opener Vacuum Switching Valve (VSV). This blocks manifold vacuum which normally draws throttle opener diaphragm and linkage rod to base idle position.
Once vehicle is started, ECM will de-energize VSV. This allows manifold vacuum to pass through VSV to throttle opener diaphragm. Diaphragm will then retract, allowing throttle linkage to return to normal base idle position.
Throttle Opener Vacuum Switching Valve
Throttle opener is controlled by Vacuum Switching Valve (VSV) which opens and closes vacuum passage to throttle opener. ECM controls throttle opener VSV according to engine, starter and coolant (water) temperature sensor signals.