96' Intrepid with Eratic RPM

Here is the OBD2 emission system drive cycle test procedure.
Engine coolant temp must be below 70c (158f) before starting the engine for either the first or second trip
The fuel level should be less than 1/2 full
First trip:
Start engine, idle for at least 1.5 minutes
Drive 3 minutes, hold b/f schdl: 1.5-2.0 msec, selector lever "3rd" eng rpm 1,800-2,000 A/C switch:ON Hold the recommended b/f schdl range. Allow road speed to vary as necessary.
Drive at 55-65 mph for 1.5 min b/f schdl 2.0-3.2 msec, selector lever "5th" Engine rpm 2,200-3,000
IGN "off" for at least 10 seconds (not more than 5 min)
Dive at 50-60 mph for 3 minutes Selector lever "4th" keep engine speed above 3,000 rpm Allow speed to vary if necessary. Do not decelerate for more than 3 consecutive seconds. A/C switch ON.
Drive at a steady state cruise of 53-58mhp b/f schdl more than 1.8 msec selector lever "5th" eng rpm 2,400-2,600
Downshift to "4th" and decel more than 5 seconds without breaking, then idle for 1 minute.
Drive two minutes b/f schdl less than 2.0 msec Accelerate to 41 mph, decelerate to 34 mph, accelerate to 41mph. Do not completely release the accelerator. A/C switch off.
Idle 1 minute in park or neutral
Drive two minutes Steady state cruise at 31-44 mph. Selector lever "4th" A/C switch OFF. Hold the accelerator pedal as steady as possible. Allow speed to change if necessary.
End of first trip. Turn the key off the begin the second trip.
Second trip:
Start engine, idle for at least 1.5 minutes
Drive 3 minutes, hold b/f schdl: 1.5-2.0 msec, selector lever "3rd" eng rpm 1,800-2,000 A/C switch:ON Hold the recommended b/f schdl range. Allow road speed to vary as necessary.
Drive at 55-65 mph for 1.5 min b/f schdl 2.0-3.2 msec, selector lever "5th" Engine rpm 2,200-3,000
IGN "off" add four gallons of fuel
Dive at 50-60 mph for 3 minutes Selector lever "4th" keep engine speed above 3,000 rpm Allow speed to vary if necessary. Do not decelerate for more than 3 consecutive seconds. A/C switch ON.
Drive at a steady state cruise of 53-58mhp b/f schdl more than 1.8 msec selector lever "5th" eng rpm 2,400-2,600
Downshift to "4th" and decel more than 5 seconds without breaking, then idle for 1 minute.
Drive two minutes b/f schdl less than 2.0 msec Accelerate to 41 mph, decelerate to 34 mph, accelerate to 41mph. Do not completely release the accelerator. A/C switch off.
Idle 1 minute in park or neutral
Drive two minutes Steady state cruise at 31-44 mph. Selector lever "4th" A/C switch OFF. Hold the accelerator pedal as steady as possible. Allow speed to change if necessary. I especially like the part where they want you to add four gallons of fuel. Not three gallons, not five gallons, four gallons. Gotta love those Nissan engineers. ...and of course they state that if the trace is not followed exactly (i.e. you botch the acceleration/deceleration) you have to start all over again from scratch

I have a 2000 malibu 3.1, and it idles at about 650 rpms. good-day ! all runs fine.

This sound as if it may be the IAC or idle air control valve which is located just behind where the air intake hose attaches to the throttle body. This is a switch that tells the computer how fast the car should idle and adjust the air intake to keep the idle steady. If you go to one of the car part websites you can look up the IAC and see what it looks like for your particular vehicle. Autozone, Checker, Oreiley all have websites.

Check your throtle postition sensor. It monitors what postion the throtle is at and sends that info to the ecm. It will go bad and cause that problem.

Check cold air intake sensor and it maybe need to be cleaned up or changed.Also check gas pedal.

Check your throttle position sensor

have your idle air control valve checked. on my 5.2 v8 is located on back of throttle body. My hardware was loose. DO NOT OVER tighten,follow torque spec in manual.

Before you go changing the idle motor, clean the throttle body out with a spray cleaner and make sure you get into the idle speed motor orifice. Spray the cleaner into the throttle body with the engine off, do'nt be afraid to use it all then let it sit awhile. When you try to start the car it might not want to start, just keep your foot all the way down on the gas pedal and as it starts and clears up just release the pedal slowly. If the car smokes out of the exhaust, thats normal. Hope this works.

sounds more likley you have an air leak this will cause bad starting as it is sucking air in instead of fuel when its cold and wnen it warms up idling will be eratic and misfire check all hoses gaskets relating to the inlet manifold or if its done that kind of mileage crankcase pressure could be the problem but i suspect an air leak yates210456

Hi
your problem seems very easy :) hope this one work with your envoy. Just buy AC DELCO carburetor tune-up conditioner.

How you use it: engine running , AC off please

1. detached the big black airflow hose which is attached in the mannifold of the engine block.

2. ask your friend to step on the gas pedal and set the rpm steady in 2000 rpm only.

3. then spray vigorously in 8 seconds the inside circle opening of mannifold while your friend steady step on gas pedal with steady 2000 RPM only.

4. after you spray, let your freind continue on gas pedal with 2000 rpm for 15 more seconds.

5. attached back the airflow big black hose to the manifold and you are ready to roll with your AC on.

if this one doesnt work, please scan your envoy by scanner called TECH II. and find out.