Any tips for why i would have a high(fast)2,500-3000 rpm's idle after changing water pump on a 91 wrangler?

The ECM maybe stuck, disconnect the battery and wait 5 mins then reconnect.

Other things that normal cause high rpm at idle:

• PCV hose to throttle body has a leak
• vacuum line to brake has a leak.
• the throttle plate maybe dirty and is open partly
• the IAC is bad. Which is on the throttle body.
• the throttle plate sensor is bad, just unplug it and see if the rpm goes down. If it does, replace the sensor.
• the egr value maybe stuck
• bad front o2 sensor
• bad coolant senor. You should have this replace since the original sensor where plastic tip and crack. The new ones has a brass tip. the transmission and air( IAT) have the same sensor part.

This is normally the way it is suppose to work. You need to have the RPM measured for High RPM and duration. What you are describing is how an electronic choke is suppose to work.

The errors would be how high the RPM goes and for how long it lasts. When cold the RPM, fuel mix and timing are changed to give a rich fuel mix. As the O2 sensors warm(Could be defective) they signal the engine to lean up. The water thermostat also has something to do changing the engine to a lean running slow condition.

If obtaining heat from your heater seems to take Forever, the thermostat could be weak. This would coincide with the engine continuing at a high RPM longer because it is not warming up.

if you have a high idle it is a bad idle air control vavle

Most carb. engines should idle between 725 and 750 R.P.M., lower the idle and be sure to check the timing. You should have an emissions label under the hood to explain the idle and timing.

If this vehicle has a clutch type fan it is probably the problem, good at idle but once the rpm's speed up it does not keep up with engine speed, thats why it heats up at highway speed.
Difficult to diagnose because you cant always tell if it is spinning as fast as it is supposed to be.


I’m happy to assist further over the phone at https://www.6ya.com/expert/gregg_78ecbb34e27be215

you check for miss how is compression

check the idle speed sensor also the map sensor

The check gauges light is normal because at 400 rpm it isn't running fast enough to build sufficient oil pressure. I am guessing maybe a vaccum leak???

sounds like you have a major vacuum leak. Plug the throttle body completly with you hand. If the car does not stall out there is you idle problem. Take carb cleaner spray vacuum like throttle body gasket intake gasket etc. Hope this helps please rate me.

check maf and tps sensor