hit brakes, making sharp turn, low idle, bogs down and stalls (1 Viewer)

[amer28]

greetings and thanks for any help. 73 FJ40 with 86 350 chevy 4 bolt motor. Was doing this once in a while now about 50 percent of time.

When I slow down to take a turn onto a cross street I hit the brakes of course and turn 90 degrees. About half the time I do this my idle goes lower and lower and sometimes truck shuts off. Idle norammly set at 1000 - I like it a little high.

I have tried going straight and just coasting to a stop and it never lowers idle. It almost never does it when I am going straight and hits brakes but does do it sometimes. Sometimes when just turn it wont do it. Confusing. But if I slow down and it brake it does i more and more lately. Kinda feels like loosing gas or vacuum?? issue to carb - brakes????

Any ideas?? Thanks for any help.

 

[GeologistFelix]

I know next to nothing about chevy motors, but...

Do you have a sight glass for the float on your carb? If so, where is the fuel level? If you have a low fuel level in there, it would tend to slosh around in the conditions you're describing, and the engine wouldn't be able to get fuel.

Also, a vacuum leak could do it.

Medium 'all the time' vac leak + load on the engine from power steering + demand for vacuum from brake booster = engine gets seriously leaned out while the RPMs drop, and it can't (or can only just barely) keep itself running.

No idea how you'd test those on your engine, but those are two theories that come to mind.

 

[Fast Eddy]

Brake booster has an internal leak.

 

[FF LC FREAK]

Brake booster has an internal leak.

Yep. Lots of options for a new booster. Mini truck seems to be the most popular.

 

[amer28]

thanks for replies. Seems checking break booster is next step. Have not looked at it but would plugging off the vaccum line from carb to booster (just to test and see if it keeps stalling) make any sense if possible?? Is it possible its a leak in line? Or is it - break booster leak - thats it - done. Thanks again.

 

[subzali]

you could try disconnecting the line to the brake booster and plugging it, but be careful because you won't have power brakes.

 

[bikersmurf]

Yes, plugging off the line would help to diagnose. BEWARE... Just to state the obvious, you won't have vacuum assist so it will be harder to stop.

What carb are you running? My stock 2 barrel would stall when I jumped on the brakes... The fact that 5 lobes were worn off the cam was likely a factor.

Float level, sloshing fuel, vacuum leaks, and ground issues may all be factors.

 

[bikersmurf]

you could try disconnecting the line to the brake booster and plugging it, but be careful because you won't have power brakes.

You beat me this time.

 

[amer28]

Thanks all - I'll test - carefully - tonight.

One question - "ground issues"?? As in "negative ground" ? Could you explain - curious.

Thanks

 

[bikersmurf]

Yes, negative ground. Bad grounds can cause all sorts of weird intermittent problems. Just trying to consider all the possible sources of the problem.









Oh, and when I replaced the cam and dropped on a Quadrajet it was a completely different beast and didn't stall anymore.