'98 High Idle Speed at Cold Start

[oyovillage]

Anybody know anything about high idle speed (1500 rpm +/-) at initial engine startup, for '98 Avalon?

Idle speed drops to normal (700 rpm +/-) after a few minutes of runtime.

(Service manual addresses idle speed when engine is warmed up.)

Thanks in advance for any info.

[artbuc]

Originally Posted by oyovillage

Anybody know anything about high idle speed (1500 rpm +/-) at initial engine startup, for '98 Avalon?

Idle speed drops to normal (700 rpm +/-) after a few minutes of runtime.

(Service manual addresses idle speed when engine is warmed up.)

Thanks in advance for any info.

I have the same problem with my 99 XLS (actually worse at 17-1800 rpm). It started doing this about 5 or 6 years ago. I have researched this extensively and confirmed all sensors in my idle circuit are working properly. If your idle control is working normally in all other regards (eg holds idle speed when A/C is turned on, etc), you probably have the same problem I have - a faulty ECU module. Many have said that a 1500 fast idle speed is normal but I do not believe it. My wife's car is a lexus RX300 with the same engine. It fast idles at 1100 rpm which seems right. My Avalon's excessive fast idle makes the car difficult to drive on cold mornings - a real pin in the butt. However, not worth spending the money for a new ECU module.

The ECU is preprogrammed to set an initial fast idle speed based on engine coolant temp. As the ECT warms up the ECU steps down idle speed. When eng temp reaches normal, the fast idle circuit goes off and other engine parameters control idle speed via the IACV.

[oyovillage]

Originally Posted by artbuc

I have the same problem with my 99 XLS (actually worse at 17-1800 rpm). It started doing this about 5 or 6 years ago. I have researched this extensively and confirmed all sensors in my idle circuit are working properly. If your idle control is working normally in all other regards (eg holds idle speed when A/C is turned on, etc), you probably have the same problem I have - a faulty ECU module. Many have said that a 1500 fast idle speed is normal but I do not believe it. My wife's car is a lexus RX300 with the same engine. It fast idles at 1100 rpm which seems right. My Avalon's excessive fast idle makes the car difficult to drive on cold mornings - a real pin in the butt. However, not worth spending the money for a new ECU module.

The ECU is preprogrammed to set an initial fast idle speed based on engine coolant temp. As the ECT warms up the ECU steps down idle speed. When eng temp reaches normal, the fast idle circuit goes off and other engine parameters control idle speed via the IACV.

Did you check the coolant temp and other sensors using OBDII Scan Tool? (Not to be confused with a simpler OBDII Code Reader)

I have not done this yet, but have read that a Scan Tool can read actual sensor data while engine is running, so that you could for instance see what the engine coolant temp sensor is actually reporting to the ECU.

[Jigg007]

Does it matter the temperature when its cold for the cold idle? Like is there a threshold for when it just kicks in for a cold idle or is it linear/logarithmic with outside/coolant temp?

I'm thinking the later because when its 40~ degrees outside Id say my idle is around 1200-1400 abouts, but when its closer to 0 and 10 the idle is 1700+

Which when its near that 2000rpm mark the car idles down the road at like 20mph, haha.

EDIT: Oh, and for OBDII scanning you can pick up a device that will convert OBDII infomation/plug into serial or USB interface for a laptop. You can read all sort of sensor values, and even freezeframe data, its really neat.

[sarsman45]

Originally Posted by oyovillage

Anybody know anything about high idle speed (1500 rpm +/-) at initial engine startup, for '98 Avalon?

Idle speed drops to normal (700 rpm +/-) after a few minutes of runtime.

(Service manual addresses idle speed when engine is warmed up.)

Thanks in advance for any info.

I have the same problem with cold starts on my '96. I have asked my mechaninc (since it revs from 1500-1800 range on cold starts) and he says that normal (given the age of my car, temperature of the engine, and the outside air.) I dont think you should worry too much since it does return to the normal operating range. As long as your car runs, its all good! (my fuel pump circuit is a little messed up so sometimes it stalls on startup.)

[artbuc]

Originally Posted by oyovillage

Did you check the coolant temp and other sensors using OBDII Scan Tool? (Not to be confused with a simpler OBDII Code Reader)

I have not done this yet, but have read that a Scan Tool can read actual sensor data while engine is running, so that you could for instance see what the engine coolant temp sensor is actually reporting to the ECU.

I checked the ECT sensor with an ohmmeter. Also swapped ECT sensors (Rx and Avalon). ECT sensor is not the problem.

[artbuc]

Originally Posted by sarsman45

I have the same problem with cold starts on my '96. I have asked my mechaninc (since it revs from 1500-1800 range on cold starts) and he says that normal (given the age of my car, temperature of the engine, and the outside air.) I dont think you should worry too much since it does return to the normal operating range. As long as your car runs, its all good! (my fuel pump circuit is a little messed up so sometimes it stalls on startup.)

I agree it isn't anything to worry about since the problem is confined to the cold fast idle circuit. However, dropping it into drive with the engine revving at 1800 rpm can't be doing the trans any good. Also, braking at that first stop sign before the engine warms up is a pain.

[TMack409]

Originally Posted by artbuc

The ECU is preprogrammed to set an initial fast idle speed based on engine coolant temp. As the ECT warms up the ECU steps down idle speed. When eng temp reaches normal, the fast idle circuit goes off and other engine parameters control idle speed via the IACV.

The type of engine oil you use has more to do with this cold start, high idle speed than anything else you can affect.

When I bought my car (used in 1998) it had dino oil in it (prolly 10W30) and I never noticed a problem with high idle. On the very first oil change, I switched to synthetic oil and the cold morning, cold-start idle rpms jumped thru the roof. Failing to make the connection, I took it to the dealer and complained. They found nothing wrong and said they had tried over the years to "fix" this "condition" - to no avail. It is a function of the coolant temp sensor and the ECU. Nothing can be done about it. Except use thicker, dino oil - which is not very efficient.