Strange noise

[papadave]

I own a 97 xl explorer auto,4.0 liter. The vehicle works fine motor wise until the outside temp.gets below 20 or so degrees then sometimes there is a sound like a low volume fog horn that comes from the under side of the drivers side and will only last for 15-20 sec. unless you step on the gas feed. This only happens when iddling. Have replaced fuel pump & fuel filter and are looking for other suggestions

 

[sparky2263]

Article No.
98-1-18

01/19/98

NOISE - "BOOMING" NOISE AT 700-800 RPMS
DURING COLD START - 4.0L SOHC VEHICLES

LIGHT TRUCK:
1997-98 EXPLORER

CALIBRATION:
7-58C-R11, 7-58V-R11, 8-58C-R05, 8-58V-R05

WARNING : THIS MODIFICATION IS AUTHORIZED ONLY FOR THE LISTED ENGINE. PERFORMING THIS MODIFICATION ON OTHER ENGINE CALIBRATIONS IS UNAUTHORIZED AND COULD CREATE LIABILITY UNDER APPLICABLE FEDERAL OR LOCAL LAWS.

This TSB lists the latest level calibrations, all past revision levels are also included.

ISSUE:
An audible "booming" noise may be heard at an idle with engine speeds between 700-800 rpms on cold startups on some vehicles. This may be caused by a resonance within the exhaust system.

ACTION:
Reprogram the Powertrain Control Module (PCM). The revised calibration will limit the amount of time the vehicle's rpm stays in the critical range which is causing the noise. Refer to the Recalibration Cross Reference Chart for the correct PCM calibration.

Perform all normal diagnostics as outlined in the appropriate Explorer Workshop Manual.

Obtain an Authorized Modification Decal (FPS 8262 - obtainable through DOES II, 25/pkg) and list the date, dealer number, and summary of modifications performed. Select a prominent place adjacent to the Vehicle Emission Control Information Decal suitable for installing the Authorized Modifications Decal. Clean the area, install the decal, and cover it with a clear plastic decal shield.

NOTE : PCM REPLACEMENT IS NOT AUTHORIZED BY THIS TSB. REFER TO THE POWERTRAIN CONTROL/EMISSIONS DIAGNOSIS (PC/ED) SERVICE MANUAL FOR APPROPRIATE DIAGNOSTIC PROCEDURES IF PCM HARDWARE CONCERNS EXIST.

OTHER APPLICABLE ARTICLES: 97-7-6

 

[dogfriend]

s there is a sound like a low volume fog horn that comes from the under side of the drivers side and will only last for 15-20 sec. unless you step on the gas feed. This only happens when iddling.

Does it sound like this?

 

[Mommystrucky]

that would be your iac just replaced mine

 

[papadave]

Thanks will give it a try