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Rough And Rolling Idle Problems


mts
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Originally posted at about.com

 

 

 

Mazda 626 Rough And Rolling Idle

 

 

 

After a normal drive, 10 to 15 minutes, if I pull to a stop, and then shift to PARK, the engine stops by itself; if I don't shift to PARK and just keep the brake on, it runs fine, engine speed stays at 500 rpm, don't know if that's too low.

 

Then if I start the car again, the engine speed gauge jumps to 1,000 to 1,500 rpm upon ignition, then it would drop below 500 rpm, dangerously dangling near 0, with the engine body vibrating and shaking, as if it's going to stall, then after 3 or 4 seconds of struggling, it would come back and the speed gauge stays around 500 rpm.

 

This does not seem to happen when the car is cold, such as when I start it in the morning, engine starts at about 500 rpm, or when I drive it for a short distance. What could be the problem? Could it be that I haven't changed the timing belt? On rainy or damping days, I often hear squeak noise from the engine that sounds like loose belt, is that related to this problem?

  • 1996 Mazda 626 LX
  • 2.0-liter DOHC-16V
  • Automatic transmission
  • 69,000 miles
  • Fuel Injection
  • P/S, A/C, Cruise control
The 1996 Mazda 626 with the 2.0 liter engine and automatic transmission up to and including VIN 1YVGE**C*T5525968 had bad Mass Air Flow (MAF) sensors. Mazda has a test procedure to confirm this. Here is an excerpt from the TSB addressing this problem.

 

DESCRIPTION:

Some vehicles with over 20,000 miles may experience any or all of the symptoms listed below. This may be caused by contamination build-up on the heated elements of the mass airflow sensor (MAFS). MAFS with date codes after 5K05 (1995, October, 5th) are less susceptible to contamination. Customers complaining of these symptoms should have their vehicles inspected and, if necessary, repaired according to this bulletin.

 

 

 

SYMPTOMS:

  • MIL illumination
  • Rough Idle
  • Hesitation
  • Lack of power
  • DTC 181 (OBD I vehicles)
One thing you can try is to take the MAF out and clean it out. Go to an electronics store and get a can of Contact Cleaner. Then spray the inside of the MAF thoroughly, being careful not to get too rough with it.

 

IPB Image While you have things apart, you may as well give the throttle body a good cleaning as well. here's how to do it.

  1. Remove the throttle body. Refer to section F of the workshop manual.

    NOTE: DO NOT remove the IAC Valve (V6), ISC Valve (4cyl) or the TPS.

  2. Thoroughly clean around the IAC Valve (V6), ISC Valve (4cyl) and the Air Adjust Screw ports in the bore of the throttle body. Use a clean shop towel for cleaning.
IPB Image
  1. Apply masking tape to fully cover the IAC Valve ("6), the ISC Valve (4cyl) and the Air Adjust Screw ports in bore of the throttle body.
NOTE: The masking tape is applied to prevent cleaner from entering these ports.
  1. Looking at the back of the throttle body, cover the IAC Valve (V6), ISC Valve (4cyl) and the Air Adjust Screw pons with masking tape.
WARNING: SAFETY GLOVES AND SAFETY GLASSES MUST BE WORN WHILE WORKING WITH THIS SOLUTION.
  1. Fill a small container (glass or cup) with Heritage S.W. 1000.
NOTE: This solution must be used full strength.

 

IPB Image

  1. Place a small plastic bucket or drain pan under the throttle body and slowly pour the container of solution through the throttle body bore.
  2. Pour the solution in the bucket or drain pan back into the small container.
  3. Repeat steps 6 and 7 (five to six times).
  4. Allow the throttle body to sit for 5 minutes.
CAUTION: DO NOT immerse the throttle body or any electrical components in the solution.
  1. Use a shop towel to wipe carbon deposits from the throttle body bore and throttle valve.
NOTE: Remove all carbon deposits however, give special attention to the throttle valve to bore contact area.
  1. Repeat steps 6 - 10 if necessary.
  2. Blow the residue from the throttle body with compressed air.
  3. Remove all masking tape.
  4. Install a new gasket.
  5. Install the throttle body.
  6. Start engine and run to normal operating temperature.
  7. Inspect idle speed, adjust if necessary
I'm sure that one, or both, of these cleaning procedures will resolve your problem.
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