I recently bought a 1988 SR5 pickup with a 3vze and a 5 speed. Here's my problem. My brakes don't seem to be working correctly. The pedal is pretty hard and takes alot of effort and it doesn't seem to brake very well for all the effort applied. When I started looking into things I pulled the large vacuum line that runs from the passenger side of the intake manifold to the brake booster on the drivers side. removing the line makes no difference in the idle of the motor, or the feel of the pedal. Also it doesn't seem like there is a vacuum being drawn into the manifold through the line. I even tried to feel for vacuum directly at the port on the manifold and i found no vacuum. However there is a vacuum being drawn by many other vacuum lines coming from the manifold.

Any ideas?

Also I don't know if it matters but the truck usually seems to idle around 1400-1500 rpms.

 

no vacuum, in the line to the brake booster? i wonder if there is carbon blockage, in the intake manifold, i'm not sure if this will work on our trucks, cause I've never tried it, but with the intake piping removed, and the truck running, blip the throttle while spraying into the intake manifold, don't go too crazy cause it can be a little dangerous. don't be afraid to use the whole can, afterwards shut the truck down, and shine a light inside to see how clean it is. let the truck run a little bit to clear the system. someone may know a better way. or a better answer

 

Thanks, I'm kinda assuming that a blockage of some sort is the only thing that would keep it from pulling a vacuum cause there doesn't seem to be a leak anywhere. I just recently replaced the fuel line for the cold start injector and had to replace the intake plenum gasket and i'm sure there is no leak. This problem was around before the intake removal & replacement.

I tried it but the truck wouldn't run with the intake tube removed. I may try disconnecting the mass air flow sensor, I'm assuming that should put the ecu into closed loop and maybe it will run without the tube connected. If that doesn't work I'll probably try disconnecting the crankcase breather tube that is just before the throttle body and spraying it in through there.

Or I may just try carb cleaner through the port that the vacuum hose for the brake booster connects to.

If anyone else has any words of wisdom I am all ears.

Thanks in advance.

 

disconnecting the MAF sensor would be the solution to the no start

 

Check and see if there is a vacuum check valve between the brake booster and the intake manifold, if there is, make sure its not installed backwards. It should pull vacuum towards the intake manifold, so the brake booster always holds a vacuum, if its backwards or stuck your brakes won`t get any vacuum from the intake manifold.

 

As far as i could tell there isnt a check valve in that line. There was a check valve in another line that doesn't seem to lead to the brake booste in anyway but i cud be wrong. that check valve works properly & i will reconfirm the direction in the am

 

Well after finding a picture of the location of the vacuum line I realized that the vacuum line was connected to the wrong port. So I switched the lines and all is well. Now the truck brakes better than ever. Thanks for all the help.

 

Not all trucks had the check valve, just throwing out any ideas that i could think of. Try pulling the vacuum line for the brake booster off of the intake manifold and stick a screw driver into the vacuum port, its possible that its plugged with carbon, also remove the hose that goes to the booster and see if you can blow through it.