Surging/lurking in first gear?

Bronconnoisseur

New member
Joined
Jan 10, 2021
Messages
13
Location
Eau Claire, WI
I’ve noticed that in first gear, whether it’s in 4x4 or not, there’s a pulsating surge at times at very low speeds...like when I’m just crawling through residential streets in the snow is when it is most pronounced so I don’t know if that’s related but yep only first gear it’ll surge 1000rpm and pulsate back and forth up to like 1200-1400 and back to 1000 as many times as I let it
 
Last edited:

miesk5

96 Bronco 5.0
Staff member
Moderator
Joined
Oct 18, 2005
Messages
7,923
Location
Coronado, CA
Yo Bronconnoisseur,
Pull the vacuum line off the mod. If fluid comes out of the vacuum line your modulator is no good.
Check vacuum line to modulator from engine intake manifold source.
See Vacuum Gauge Diagnosis - BEST!; Normal engine; Steady gauge 18"-20" at all speeds..." READ MUCH MORE
Source: by Craig U @ Reading your vacuum gauge

Vacuum Modulator; The vacuum modulator is a vital component of an automatic transmission. It tells the transmission what kind of load is being put on it allowing the transmission to react with the proper line pressures and shift points. Over time, modulators can develop leaks, get ruptured diaphragms, get bent, etc. Not only can this cause annoying drivability issues, it can lead to premature transmission failure.
Inspect vacuum modulator, and it's vacuum hose back to intake manifold for leaks, etc.
It's at rear of C6, passenger side..


Screenshot_20210116-155650_Chrome.jpg
 

Bronconnoisseur

New member
Joined
Jan 10, 2021
Messages
13
Location
Eau Claire, WI
Yo Bronconnoisseur,
Pull the vacuum line off the mod. If fluid comes out of the vacuum line your modulator is no good.
Check vacuum line to modulator from engine intake manifold source.
See Vacuum Gauge Diagnosis - BEST!; Normal engine; Steady gauge 18"-20" at all speeds..." READ MUCH MORE
Source: by Craig U @ Reading your vacuum gauge

Vacuum Modulator; The vacuum modulator is a vital component of an automatic transmission. It tells the transmission what kind of load is being put on it allowing the transmission to react with the proper line pressures and shift points. Over time, modulators can develop leaks, get ruptured diaphragms, get bent, etc. Not only can this cause annoying drivability issues, it can lead to premature transmission failure.
Inspect vacuum modulator, and it's vacuum hose back to intake manifold for leaks, etc.
It's at rear of C6, passenger side..


View attachment 21985

I joined this site hoping someone like you would exist miesk5...I’ll post an update mid next week
 
Last edited:

sinker4

New member
Joined
Dec 17, 2010
Messages
17
My 95 would start then stall. On the second attempt it would start and run rough for a few seconds then smooth out as it warmed up. I replaced the original Idle Air Control valve and the problem went away
 

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