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If you have a vacuum gauge, connect it to the intake manifold. What it is the vacuum at idle with engine warmed up? If you have low manifold vacuum to begin with, activating the brake booster can kill the engine.

I found one person's perception of an engine running fine may be different than another person's. We had a customer with a dead misfire and they swore up and down the engine was running fine and had plenty of power.

I appreciate the responses. Had the transmission rebuilt around four months ago and after it was installed, truck just died on way to work, like three weeks later. After sitting for around an hour cranked back up and he discovered the distributor was shot. Replaced the distributor and everything was fine till it started stalling at stops and when you put it in gear. Replaced brake booster and just about every sensor and module including new computer on truck. Ended up buying new crate motor (original had 275,000 mileage) and after installation, still doing same thing, stalling when you put it in gear. I am thinking it is in wiring but he has so much time invested he is bound and determined to figure it out himself. Vacuum seems to be fine when he checked it.

If you are in park or neutral, if you pump the brakes it will raise rpms but if you switch into drive or reverse and hold brake, it will stall. If you hold brake lightly it doesn't stall. If you are pressing brake hard it stalls every time. Also stalls when driving in traffic and coming to red light or stop sign. After you stop the rpms will start acting erratic and then it will die. Starts right back up.

He has discovered if he unplugs the temperature sensor the truck idles fine and doesn't stall when you put it in gear. Replaced with oem but when it is plugged in it stalls when you put it in gear. He checked the check valve on booster, seem to be working properly.

I've ran into one of those where when you pressed on the brake the engine would stall out. What happened on that one was the brake lamps and the fuel pump share the same ground point on the frame. The ground had a bad connection and when the brake lights were operated that would cause the fuel pump to quit or slow down due to the voltage drop happening across the poor ground point.

Unplugging the temperature sensor (ECT) will cause the engine puter to add more fuel because it will think the engine is running cold. Maybe the low fuel pressure when the brakes are applied is being offset when you have the ECT unplugged. Just a theory.

Fuel pump ground is located somewhere in the back on the left frame rail...I believe.

You could also do a voltage drop test on the pump ground circuit to see if it has excessive voltage drop when the brakes are applied for confirmation.

Getting to be a waste here. Which sensor, one for fuel delivery that would cover the vacuum leak your booster probably causes? That or the one for a gauge which would do nothing for this.


Nothing conclusive for tests or proper anything on this so far. If someone is just going to tell you it's all fine and you believe it than why is there a problem? Thread is messed up,


T

1991? I don't think ABS messes with vacuum in power assist? Try this: Engine off, deplete power assist by depressing brake pedal till it feels hard. Hold there and start engine and pedal should fall some with renewed assist.


It should also hold power assist long after engine is shut off for a couple stops or at least one decent one. If not vacuum is leaking and everything from check valve to even new booster in question. If somehow master and booster are not compatible with pushrod to master things could be messed up there,


T

What is actually bad on it, the pump or hydraulic assembly?

from what i understand, it is the entire unit. the unit that is in there cannot be repaired.

A-1 Cardone can return and rebuild your hydraulic unit for around $500 ($100 core). Most local part houses deal with Cardone. Hopefully the mechanic diagnosed the problem to the unit itself. You can test the pump motor on the vehicle to be sure that part of the system is working.

the unit in question is called the abs accumulator hydaulic unit. is their website cardone.com?
thanks for all your help.

Thanks Discretesignals, youve been a big help.

Your welcome. Let us know how things turn out with that.

ive been in touch with cardone and they told me i can send them the unit but it first has to go thru a local dealership like napa, carquest, fisher, or autozone. ill try and contact one of them tomorrow and see what the cost/process is. ill let you know how it turns out.
thanks again