My 95' 3.9 started having power steering problems. Turning would work half way normal and then tense up. It has also began running with a hickup as I coast down the highway. A few backfires have occurred as well. It will surge and cut out.

I have replaced the computer, replaced and checked wires/plugs/cap connections, checked vacuum lines, used diff fuel, cleaned air filter. The valves sound normal.

I am thinking that my brake booster is failing. HOW DO I MEASURE the vacuum pressure??? Is it best to disconnect the main from the booster and connect the meter hose there? After checking vacuum, I will then look into the fuel pump and relay but I know I replaced the relay last summer.

 

I read that 22-25 iHM vacuum is ideal.

I disconnected the small cap plug on the booster spout (opposite of the main line)
and connected my vacuum meter there. With the engine struggling to idle, the vacuum pulls 14-17 iHM.

How can I test to find out if the vacuum is low because of the engine vs the booster?

What order do I need to test parts like... a bad valve, relay, injector, vacuum line etc?

thanks for any help.

 

The brake booster gets full vacuum right off the intake manifold. If the booster was leaking enough vacuum to drive the reading that low then you would definitely hear it whistling. Between the low vacuum and the poor engine performance I'm inclined to think your timing chain is very worn and possible jumped a tooth.