High RPM's, high idle, when driving will not coast due to high RPM's

WWOOD

MEMBER
1998 SATURN SL2
1.9L
4 CYL
2WD
AUTOMATIC
187,450 MILES

Hello. Car is experiencing high rpm's. At cold start, will get to about 1,800- to 2,100 rpm's. The rpm's steadily come back down to about 1,100. From park to drive, rpm's stay about 1,100. From drive to neutral, rpm's spike to anywhere from 2,100 to 2,300 and start to come down slowly to again 1100 rpm's. From neutral, to drive, the rpm's raise to about 1,500 rpm's, then taper back down to 1,100. After car is warm from driving there is still higher rpm's. On a flat road, the car will increase speeds without touching the gas pedal. This occurs at slower speeds, around 20 to 30 mph. At this speed, put car into neutral, the rpm's stay at about 1,800 to 1,900 without any changes even though the transmission is in neutral. Putting car back in drive, the rpm's come back down to a normal rpm based on speed. From highway speeds, the car will slow down after gas pedal has been released, however, the car does not coast like it should since the gas pedal is not being pressed. The idle air control valve has been replaced as well as the throttle body cleaned with no changes. There is not an SES light or check engine light on. Temperature gauge appears to be normal and within the normal operating range.

Saturday, January 26th, 2019 AT 7:56 PM

3 Replies

KENW1

MECHANIC
213 POSTS

Thanks for visiting2carpros.com. This may be one of two things or a combination of both.

1 A vacuum leak
2 A sticking idle air control valve.

I'll post a guide below on checking for vaccuum leaks

https://www.youtube.com/watch?time_continue=5&v=4ktw1X4W_-k

This generation of GM/Saturn vehicles also had very common idle air control valve failures. It is valve that blocks or unblocks a hole in the throttle body to allow engine speed changes independent of the throttle. When they fail the symptoms you describe can occur. Replacement is pretty straight forward. It's located on the side of the throttle body. If you follow the intake tube from the air filter you'll find it. I'll post info on that below.

REMOVAL
1. Turn ignition Off.
2. Remove air intake tube and resonator.
3. Remove electrical connector from the IAC valve.
4. Remove screws and IAC valve.

NOTE:
The IAC valve is an electrical component and must not be soaked in any liquid solvent; otherwise damage could result.

5. Remove O-ring from IAC valve and discard.

INSTALLATION

1. Clean the IAC valve seating surfaces on the throttle body to assure proper seal of the new O-ring and contact of the IAC valve flange.

2. Lubricate new Oring with clean engine oil and install on IAC valve.
3. Insert IAC valve in throttle body.
4. Install IAC valve attaching screws using thread coating, Saturn P/N 21485277 (Loctite 242 Threadlocker or equivalent).

Torque: 3 NM (27 in. lbs)

5. Connect electrical connector to IAC valve. Push in connector until a click is heard and pull back to confirm a positive engagement.

Image (Click to make bigger)

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Sunday, January 27th, 2019 AT 6:07 PM

WWOOD

MEMBER
2 POSTS

KenW1
Thanks for response. Prior to posting the question, the IAC was replaced with a Borg Warner component with no changes to rpm levels or driveability conditions. Vacuum leaks will be checked. The car is not readily available. This will not take place until later in the week around Th to Saturday.

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Sunday, January 27th, 2019 AT 6:35 PM

KENW1