My engine Lopes between 500 and 900 rpm at idle or when in drive but at a stop. 1989 C4 Auto transmission.

FORGOT TO SCAN THE PCM I SEE.
check all fuses.?
not told
fails hot and cold engine or both
car must be in transmission DRIVE selected? right?
and foot off gas pedal (accelerator)_ rpm goes to 2000 or up to 6000 rpm . and or
so driving foot off the pedal and RPM goes too high
or in drive, I step on the throttle (gas) and RPM shoots way high
and Never leaves 1st gear. that is transmission failures.
in DRIVE.
if rpm also goes that high right foot doing nothing and in park
that is engine idle control's failing.
we can not see you drive or how. so answers can be a tad hard.
in what gear? PRNDL (choices)
right foot doing what?
and what SPEED is too slow 20 or 85mph? or?
does tranny fail to upshift?

The 2.2L of that year would be the 5S-FE engine.
It used an electronic Idle Speed Control Valve.
With all of the intake/vacuum system connected connected, accessories off and the transmission in neutral connect a tachometer. Short terminals TE1 and E1 of the underhood check connector.
Wait for the idle to maintain 1000-1300 RPM for 5 seconds.
If needed adjust the idle adjust screw to an engine speed of 650+-50 RPM.

US Idle is 700+-50 RPM, CA M/T is 800+-50 RPM and CA A/T is 750+-50 RPM.

Remove jumper of E1 and TE1 of the check connector.

Hi Paul:
Here are my random observations:
- 2500 to 3000 is really high for "idle"
- Putting it into drive or reverse engages the transmission and puts load on the engine through the torque converter. Since the RPM is high enough that the vehicle thinks it should be moving, the transmission will engage and rpm will drop since more power is needed.
What to do? How long since tuneup?
History? Did this just start immediately, or did it sneak up a bit at a time.
Make, model, engine, year, Kms or miles. Give us some info and someone who is a better transmission specialist will probably kave some more ideas.
Cheers.

It may be no engine thermostat which keeps the engine temperature at a constant 180F usually. Or you have some bad connections to a temperature sensor that sends temperature information to the Ecu (brain) and controls fuel. Corrosion causes
bad connections If you have an auto parts store scan your error codes that will be a better diagnostic. It is possible a problem with transmission fluid level or quality of fluid.

That will do it. Cut back the hose just enough to get past the crack. Caps can be had at an auto parts store.

stationary rpm is to low,its normal higher the handgearbox.
too keep motor running it chould be higher so engine stay running,
while put in drive.

engine runs smooth if giving more than idle pressure. It is when the motor is engaged with transmission at start the engine lopes and wants to cut off. If I press the throttle hard it takes right off. If I come to a stop I can put transmission in neutral to keep it from cutting off. This creates a shifting that is not normal and I'm afraid it is a sign of failure coming.

RPM's up and down check EGR valve and sensor. EGR valve and sensor control idle. That's why your getting the surging on rpm's and this could be giving out the other codes. If mass flow was bad car will not start and the same for the map sensor. O2 sensor measures gas and air for right mixer. TPS controls 0-60 speed as in throttle respons.

overdrive should be activated by a solenoid ..internal and perhaps an external one also.. in 89 the computer was primitive and i dont think controlled shift points..also if engine health is bad or missing or vacuum to any cacuum modulator at trans is damaged or compromised.. these issues could occur...good luck

Here is the most common cause of surges and stalls, it is the idle speed control air-bypass valve and throttle valve, they get full of gunk over the miles and cause idle issues (stalls) like yours, Get a can of intake cleaner from any local parts store, not carb spray, intake cleaner, it is made by a company called CRC, remove the air intake hose to the engine, hold the idle high so the engine won't stall, then spray the can of cleaner into the intake while keeping the engine running, use at least 1/2 the can, shut down the engine and disconnect the battery for 5 minutes, then restart and complete a number of mixed driving cycles, town, freeway, stop and go etc., after a few days the problem will go away as the system will relearn to the clean intake.