1987 NA High Idle w/ pulsing problem

alamostation · 04-06-2007, 10:23 PM

I'm a new owner waiting on a shop manual. Before it arrives, I have a problem that I would like to fix immediately. Since I bought it a week ago, hot or cold, my engine idles around 1900 RPM. The last two days, this has become an up-down throb between 1500 and 2000. Tomorrow will be my first daylight opportunity to look at it.

I'm pretty sure I am looking at two inter-related problems. How do I decrease the idle speed in general? And what do I need to look for besides vacuum leaks as the cause for the pulsing idle speed?

chgman · 04-11-2007, 07:47 PM

Your problem may be air in the cooling system. The MR2 has an engine temp sensor that tells the ECM the status of your engine. If there is air in the cooling system it causes that sensor to send up and down messages to the ECM and you get that idle pulse. Bleed your cooling system and the pulse should go away. You will need a clear plastic tube (mine came with it). Look in the engine compartment on the drivers side of the motor above the transmission for a valve with a pet-cock on it. With the car on flat ground attach the hose to the valve and with the motor running and fully warm open the pet-cock until the fluid runs clear without air bubbles. Keep your overflow tank full while you do this or it will get worse. Keep bleeding the system until no air comes out of the tube. There is a good how to on the MR2.com website also.

Good luck!

alamostation · 04-24-2007, 08:17 AM

Problem solved. Thanx for the imput on this thread and private mail. The problem was a bad seal on the idle speed screw. Now I have a nice 750 rpm idle when warm. Next challenge: conversion to R134.

04-06-2007, 10:23 PM	#1 (permalink)
alamostation Benevelent Mad Scientist Join Date: Apr 2007 Posts: 28 Thanks: 4 Thanked 0 Times in 0 Posts iTrader Rating: (0/0% )	1987 NA High Idle w/ pulsing problem I'm a new owner waiting on a shop manual. Before it arrives, I have a problem that I would like to fix immediately. Since I bought it a week ago, hot or cold, my engine idles around 1900 RPM. The last two days, this has become an up-down throb between 1500 and 2000. Tomorrow will be my first daylight opportunity to look at it. I'm pretty sure I am looking at two inter-related problems. How do I decrease the idle speed in general? And what do I need to look for besides vacuum leaks as the cause for the pulsing idle speed?

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04-11-2007, 07:47 PM	#2 (permalink)
chgman 88MR2SC Enthusiast Join Date: Apr 2007 Location: SF Bay Area Posts: 10 Thanks: 0 Thanked 1 Time in 1 Post iTrader Rating: (0/0% )	Your problem may be air in the cooling system. The MR2 has an engine temp sensor that tells the ECM the status of your engine. If there is air in the cooling system it causes that sensor to send up and down messages to the ECM and you get that idle pulse. Bleed your cooling system and the pulse should go away. You will need a clear plastic tube (mine came with it). Look in the engine compartment on the drivers side of the motor above the transmission for a valve with a pet-cock on it. With the car on flat ground attach the hose to the valve and with the motor running and fully warm open the pet-cock until the fluid runs clear without air bubbles. Keep your overflow tank full while you do this or it will get worse. Keep bleeding the system until no air comes out of the tube. There is a good how to on the MR2.com website also. Good luck!

04-24-2007, 08:17 AM	#3 (permalink)
alamostation Benevelent Mad Scientist Join Date: Apr 2007 Posts: 28 Thanks: 4 Thanked 0 Times in 0 Posts iTrader Rating: (0/0% )	Problem solved. Thanx for the imput on this thread and private mail. The problem was a bad seal on the idle speed screw. Now I have a nice 750 rpm idle when warm. Next challenge: conversion to R134.