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1993 Bronco XLT 5.8l
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Discussion Starter #1
Hello everyone,
I’m getting a loud vacuum leak type of noise on my 1993 5.8 that goes away when I give the truck throttle. I’m not sure if it’s actually a vacuum leak, just sounds a lot like one. I can’t find any leaks anywhere, anyone got any ideas?
 

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What you are describing sounds 100% like a cracked flexplate. When these crack, the noise from them goes away with throttle.
 

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Registered
1993 Bronco XLT 5.8l
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4 Posts
Discussion Starter #4
What you are describing sounds 100% like a cracked flexplate. When these crack, the noise from them goes away with throttle.
It’s more of a consistent air flow noise then a chirping or knocking, that’s the only reason I don’t think it’s the flex plate
 

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Back in 1993 on my trip to South Carolina, I had the same exact thing... started as whirling nose. 2000 miles later, it started the knock on the deceleration and nothing on the acceleration. Steady throttle, it was evident.
 

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26,956 Posts
Yo Nick,
Welcome!

See my Vacuum leak test in post #11 incl jowens126's HVAC Control Panel info & Mikey350's tests @ Help with dtc codes and idle

Excerpts:
One way to do a quick check is to grab a vacuum gauge. Some parts stores will loan you a gauge with refundable deposit.
The vacuum gauge should read between 15 and 22 in-Hg depending upon the engine condition and the altitude at which the test is performed. SUBTRACT ONE INCH FROM THE SPECIFIED READING FOR EVERY 1,000 FEET OF ELEVATION ABOVE SEA LEVEL.
The reading should be quite steady. .
When engine is rapidly accelerated (dotted needle), needle will drop to a low (not to zero) reading. When throttle is suddenly released, the needle will snap back up to a higher than normal figure.

When vacuum leaks are indicated, search out and correct the condition. Excess air leaking into the system will upset the fuel mixture and cause conditions such as rough idle, missing on acceleration, or burned valves. If the leak exists in an accessory unit, such as the power brake, the unit will not function correctly. Or Air Conditioning when in MAX mode may switch to Defrost.

If you have the E4OD, Transmission Control Indicator Light (TCIL) is a LED with an overdrive on/off switch at end of the Transmission shifter stalk; flashing OD light is an indication of a transmission related trouble code in the Powertrain Control Module (PCM).
Is it flashing while driving?

Try a Self Test for Diagnostic Trouble Codes (DTC)s by my pal, BroncoJoe19 @ Code Reader
●□●
Find out if speed control, if equipped, recall work completed. Check @ Recalls Look-up by VIN (Vehicle Identification Number); or @ Welcome to Ford Owner | Official Ford Owner Site; or ... have VIN ready. While there, see most Ford dealer maintenance/repairs done @ any dealership nation-wide.
"Summary: ON CERTAIN PICKUP TRUCKS, PASSENGER VEHICLES, SPORT UTILITY VEHICLES, AND MOTOR HOMES CHASSIS, THE SPEED CONTROL DEACTIVATION SWITCH MAY, UNDER CERTAIN CONDITIONS, LEAK INTERNALLY AND THEN OVERHEAT, SMOKE, OR BURN. THIS COULD RESULT IN AN UNDERHOOD FIRE."
See this guide by jowens1126 to confirm recall status @ 93 & 94-96 Cruise Control Recalls Repair
Note that the 93 recall is different than 94-96.

For any Bronco questions or to chat about desired modifications or build, it's better to post each seperately in Noobie Bronco Tech Questions. Flame free zone. This will get more attention and you can build up your post count to get into other sections such as Bronco and Ford Parts/Accessories (75 posts required to participate due to scammers who preyed on our members ).

Here is the 1993 Bronco Dealer Brochure in Google Drive @ 93Bronco.pdf

1993 Bronco Dealer Training Video via silver70 @

1993 Bronco, Venezuela Commercial @

Our Forum FAQs includes for example, How To Upload Images To Posts & How to Use Search. See more tips!

Baba Looey's Favorite FSB Links (lots and lots of tech links)including, "how do I get the tailgate glass to...", etc

Try to find time to participate in our Full-Size of the Month Contest and current Full-Size of the Year Contest @ Voting
See pictures & build info of each Bronco nominated.
You will get ideas by those competing. Also see the prizes! They are awesome as compared to other sites' "contests"!
Al
 

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Registered
1993 Bronco XLT 5.8l
Joined
·
4 Posts
Discussion Starter #7
Yo Nick,
Welcome!

See my Vacuum leak test in post #11 incl jowens126's HVAC Control Panel info & Mikey350's tests @ Help with dtc codes and idle

Excerpts:
One way to do a quick check is to grab a vacuum gauge. Some parts stores will loan you a gauge with refundable deposit.
The vacuum gauge should read between 15 and 22 in-Hg depending upon the engine condition and the altitude at which the test is performed. SUBTRACT ONE INCH FROM THE SPECIFIED READING FOR EVERY 1,000 FEET OF ELEVATION ABOVE SEA LEVEL.
The reading should be quite steady. .
When engine is rapidly accelerated (dotted needle), needle will drop to a low (not to zero) reading. When throttle is suddenly released, the needle will snap back up to a higher than normal figure.

When vacuum leaks are indicated, search out and correct the condition. Excess air leaking into the system will upset the fuel mixture and cause conditions such as rough idle, missing on acceleration, or burned valves. If the leak exists in an accessory unit, such as the power brake, the unit will not function correctly. Or Air Conditioning when in MAX mode may switch to Defrost.

If you have the E4OD, Transmission Control Indicator Light (TCIL) is a LED with an overdrive on/off switch at end of the Transmission shifter stalk; flashing OD light is an indication of a transmission related trouble code in the Powertrain Control Module (PCM).
Is it flashing while driving?

Try a Self Test for Diagnostic Trouble Codes (DTC)s by my pal, BroncoJoe19 @ Code Reader
●□●
Find out if speed control, if equipped, recall work completed. Check @ Recalls Look-up by VIN (Vehicle Identification Number); or @ Welcome to Ford Owner | Official Ford Owner Site; or ... have VIN ready. While there, see most Ford dealer maintenance/repairs done @ any dealership nation-wide.
"Summary: ON CERTAIN PICKUP TRUCKS, PASSENGER VEHICLES, SPORT UTILITY VEHICLES, AND MOTOR HOMES CHASSIS, THE SPEED CONTROL DEACTIVATION SWITCH MAY, UNDER CERTAIN CONDITIONS, LEAK INTERNALLY AND THEN OVERHEAT, SMOKE, OR BURN. THIS COULD RESULT IN AN UNDERHOOD FIRE."
See this guide by jowens1126 to confirm recall status @ 93 & 94-96 Cruise Control Recalls Repair
Note that the 93 recall is different than 94-96.

For any Bronco questions or to chat about desired modifications or build, it's better to post each seperately in Noobie Bronco Tech Questions. Flame free zone. This will get more attention and you can build up your post count to get into other sections such as Bronco and Ford Parts/Accessories (75 posts required to participate due to scammers who preyed on our members ).

Here is the 1993 Bronco Dealer Brochure in Google Drive @ 93Bronco.pdf

1993 Bronco Dealer Training Video via silver70 @

1993 Bronco, Venezuela Commercial @

Our Forum FAQs includes for example, How To Upload Images To Posts & How to Use Search. See more tips!

Baba Looey's Favorite FSB Links (lots and lots of tech links)including, "how do I get the tailgate glass to...", etc

Try to find time to participate in our Full-Size of the Month Contest and current Full-Size of the Year Contest @ Voting
See pictures & build info of each Bronco nominated.
You will get ideas by those competing. Also see the prizes! They are awesome as compared to other sites' "contests"!
Al
Thank you! Much appreciated. So I feel like an idiot, but I came across a separate post about similar issues being cause by loose bolts on the upper intake manifold. Low and behold, my back right bolt was very loose. Tightened it up a little bit and the noise is gone and my idle has shot down to 1500 rpm. I’m still gonna test for vacuum leaks just in case, because I guarantee I probably have one. Thank you everyone for the help!
 
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