alright i have posted before and i have checked other posts and i cant figure out what it is...i cleaned out my IACV and it didnt do anything really...i was told it might be my fast idle thermo valve...what happens is it revs up to about 3,700 rpm and sits there for a sec while it warms up and then drops to about 1200 and back up to 2700 rpm and repeats itself over and over...dont know what it is...spark plugs/wires? distributor? tps? fast idle thermo vavle? somebody help!
RoadRacer02
Fluctuating Idle?
Here's a list of possibilities in order of cause of problem...
WHEN COLD FAST IDLE OUT OF SPEC (norm = 1,000-2,000rpm)
1.) Fast Idle Thermo Valve
2.) Idle Air Control Valve
3.) Idle Adjustment Screw
WHEN WARM RPM TO HIGH
1.) Idle Air Control Valve
2.) Fast Idle Thermo Valve
3.) Power Steering Pressure Switch Signal
Hoses and connections
Idle Adjustment Screw
INSPECTIoN
Fast Idle Thermo valve
1.) Remove the intake from the throttle body
2.) Start engine
3.) Put your finger over the lower port in the throttle body and make sure that there is air flow with the engine cold (engine coolant temp below 85F).
![Image]()
If not then replace the fast thermo idle valve and reset
4.) Start car and hold engine at 3,000 rpm with NO load (tranny in park or netural) ultil the radiator fan comes on, then let idle.
5.) Check that the valve is completely closed. If not, air suction can be felt at the lower port in the throttle body.
----> if any suction is felt check coolant level and for air in the coolant system. If ok then replace the fast thermo idle valve
WHEN COLD FAST IDLE OUT OF SPEC (norm = 1,000-2,000rpm)
1.) Fast Idle Thermo Valve
2.) Idle Air Control Valve
3.) Idle Adjustment Screw
WHEN WARM RPM TO HIGH
1.) Idle Air Control Valve
2.) Fast Idle Thermo Valve
3.) Power Steering Pressure Switch Signal
Hoses and connections
Idle Adjustment Screw
INSPECTIoN
Fast Idle Thermo valve
1.) Remove the intake from the throttle body
2.) Start engine
3.) Put your finger over the lower port in the throttle body and make sure that there is air flow with the engine cold (engine coolant temp below 85F).
If not then replace the fast thermo idle valve and reset
4.) Start car and hold engine at 3,000 rpm with NO load (tranny in park or netural) ultil the radiator fan comes on, then let idle.
5.) Check that the valve is completely closed. If not, air suction can be felt at the lower port in the throttle body.
----> if any suction is felt check coolant level and for air in the coolant system. If ok then replace the fast thermo idle valve
He's right... check all of that, but also check the PCV Valve and rubber line from your valve cover to your intake manifold. I started my LS without it connected just the other day after I threw on an older valve cover (while mine was being powdercoated), and it did the same exact thing I thought it would.... started with a high RPM, and then bounced to 2700, as the vacuum in the line surged. May be worth a shot.
Good Luck
Z
Good Luck
Z
i had that problem
it was my IM gasket it needed to b replaced badly. i so replaced it, problem fixed. do this, when ur car is jumping idles like that pop ur hood and put ur ear near the IM if u hear any air then thats where ur problem is at. but my problem was with the IM gasket
it was my IM gasket it needed to b replaced badly. i so replaced it, problem fixed. do this, when ur car is jumping idles like that pop ur hood and put ur ear near the IM if u hear any air then thats where ur problem is at. but my problem was with the IM gasket
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