Engine stalls when braking or idle (1 Viewer)

Joined
Jun 11, 2011
Messages
54
Location
Bakersfield
I was hoping I could get some help from the forums. I have an issue with engine stalling when braking and it stalls periodically when at idle. Pretty scary situation when it happens especially while vehicle is still moving. Oil pressure gauge is dropping very low after the engine warms up. The engine runs perfect when driving above 1500 rpm and you would never expect it to have problems.

What I have done:
I have done some research and have checked all vacuum lines and everything appears to look good. I also checked break booster hoses and intake hoses and I do not see any cracks. However, when I removed the intake hose I saw a "T" for vacuum line exposed with no line attached underneath the throttle body. There is orange connectors and one side is not connected but I do not see any hoses to attach to it. But it is very tight and I don't want to take apart the throttle body. I will attempt to add picture of what I saw. Any help is appreciate.

image.jpeg
 
Joined
Jun 11, 2011
Messages
54
Location
Bakersfield
Awesome I see where the missing goes, not if I can figure a way to get to it. Otherwise I'm going to have to do some wrenching
 
Joined
Jun 29, 2009
Messages
525
Will most likely fix it completely. A missing bolt in my egr made it run so bad, I had to time the lights to get home.

Replaced the bolt, all good.

Throttle body is 4 bolts that are easy to reach. You don't have to undo the throttle cables either. Just take the 4 bolts out and move it out of the way. You'll be abke to see it.
 
Joined
Feb 2, 2004
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10,975
Location
Washington
I think there is something going on with the brake booster/master cylinder we are starting to see vacuum leaks on these trucks now that they are getting old. I think this is the 3rd or 4th post I have seen with vaguely similar issues, where when the person is on the brakes and or turning at idle the engine will die. Do you have the sinking pedal on occasion as well?
 
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Joined
Jan 6, 2013
Messages
1,811
Location
Golden, CO
I just replaced my booster. Was failing slowly. Eventually wouldn't hold vacuum more than a few seconds after shutoff. Then it started randomly not providing assist which got scary. No problems with idle though.

Also, my brakes are awesome now. I replaced the master too at the same time.
 
Joined
Jun 11, 2011
Messages
54
Location
Bakersfield
I think there is something going on with the brake booster/master cylinder we are starting to see vacuum leaks on these trucks now that they are getting old. I think this is the 3rd or 4th post I have seen with vaguely similar issues, where when the person is on the brakes and or turning at idle the engine will die. Do you have the sinking pedal on occasion as well?

I do feel weakness in the brake pedal on occasions and i end up pumping the brake.
 
Joined
Jan 6, 2013
Messages
1,811
Location
Golden, CO
That's indicative of a bad master cylinder. That wouldn't cause the engine trouble though. A bad booster would give you a firm pedal that results in very weak braking. The booster could potentially cause the engine trouble. It's possible both are failing.
 
Joined
Sep 15, 2012
Messages
77
Location
Woodland Hills, Utah
I'm with @scottryana on this one. When you apply the brakes at idle and it results in your rpm's dropping, booster is bad.
I have been chasing intermittent low rpm to the point of stalling on my 97 LC. 270000 on the clock. It happens only when the truck is hot and when I use the brakes coming to a stop at the bottom of an off ramp, or at the top of a hill. Never does it at a plain standstill. Reading this thread, I realized it's only happening only when brakes are applied. Never occurred to me it could be the booster. I've checked all vacuum hoses. EGR system etc. I replaced the Idle air control valve. no results. I ordered an after market booster. If that doesn't solve it, I will install it on my LX 450 because I already know that booster is toast ( when it's real cold it hisses when I apply brakes.) I will post results next week when I install the new booster.
 
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