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Question

1997 Jeep Grand Cherokee. Idles rough in park and even rougher in drive.

Submitted: 540 days and 4 hours ago.
Category: Car
Value: $9
Status: AWAITING CUSTOMER ACTION
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Optional Information

Optional Information:
1997 Jeep 4x4 4.0

Posted by OnlineHelp 540 days and 4 hours ago.

Info Request

Hello and thank you for choosing Just Answer.

Do you have a check engine light that is on?

Other than idle problems, are there any other symptoms while driving?

540 days and 4 hours ago.

Reply

No the check engine light is not on.

None that I am aware of.

Accepted Answer

Thank you.

You need to inspect/replace your idle air control valve. This valve is located on the throttle body. It allows air to bypass the throttle plate when the gas pedal is not pushed and the throttle is closed. This allows the car to stay running, however if this valve is clogged or dirty you may experience stalling while idling.

The Idle Air Control valve, or IAC valve is mounted on the back of the throttle body. The valve controls the idle speed of the engine by controlling the amount of air flowing through the air control passage. There is a factory pre-set throttle screw located by the valve which is not connected with the valve and should never be tampered with.

The IAC valve consists of electronic motors that move a pintle shaped plunger in and out of the air control passage. The valve receives an electronic signal from the PCM.

When the valve plunger is moved in, the air control passage flows more air. This raises the idle speed. When the valve plunger is moved out, the air control passage flows less air. This lowers the idle speed.

  1. Remove the air intake duct at the throttle body.

  2. Disengage the IAC valve wiring connector, remove the two mounting screws and carefully pull the valve from the throttle body.

  3. Installation is the reverse of removal.

Removing
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Removing the IAC valve from the throttle body

Picture
Expert: OnlineHelp
Pos. Feedback: 99.0 %
Accepts: 
Answered: 5/31/2008

Mechanic

Mechanic

539 days and 21 hours ago.

Reply

Reply to OnlineMechanic's Post: replaced the IAC and the problem still exists. Now the engine light comes on blinks every now and again. In drive the idle is 250 rpm and feels extremely out of time.
Whats next?

Posted by OnlineHelp 539 days and 21 hours ago.

Info Request

Okay the blinking check engine light indicates that the car is misfiring. You may want to inspect the timing chain and see if it may have jumped.

Also does the engine light come on as soon as you turn the car on?

536 days and 21 hours ago.

Reply

YES, REPLACED THE PLUG WIRES, STILL ROUGH, 250 RPM ALMOST WANTS TO DIE. WHEN PULLING THE NUMBER 3 PLUG WIRE THE ENGINE ALMOST WANTS TO DIE, PULL ANY OTHER PLUG WIRE, ENGINE STILL IDLES ROUGH BUT DOESN'T WANT TO DIE.

Posted by OnlineHelp 536 days and 11 hours ago.

Answer

Do you have a spark tester, so that you can check for spark. The fact that little change happens when you pull all others would indicate they are misfiring.

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