Leaking brake booster

[Oldman]

Can anyone tell me how to test a brake booster for a vacuum leak? I'm still trying to find the reason for my lean condition and am thinking it might be the power brake booster. I don't have a scan tool, so I can't just plug the line and check it out.
Any help would be appreciated.
And no, I haven't really noticed any change in the feel of the pedal.
Thanks,

[justin85]

What exactly is going on with your car? What you mean by lean?
Can you explain a little more plz,
Is it your brakes or O2?

[Oldman]

I have a code (I think it's P0171) that indicates a lean condition. I've replaced all vacuum lines and MAF and O2 sensor. Still trying to determine if it's a vacuum leak or fuel pressure problem.

[myfirstbonnie]

Have you sprayed carb cleaner around the LIM and SC to see if you have a bad gasket? If you spray and the idle changes, then there is a leak. Do this to all the vacuum fittings, SC, LIM, TB, fuel injectors and any where else there is a gasket or seal to the induction side.

[Oldman]

Yeah, I've done all that. I've smoked the engine too (see my other posts). Lots of posts. Tried lots of things. Not finding any answers. Car seems to be running good. Tired of seeing that light on the dash telling me there's a problem. Gas mileage seems to be off a little, but other than that car seems fine.

[Jfridge92]

Not sure if I missed this in your other post, but if you haven't already, go rent a fuel pressure tester from autozone and test your fuel pressure. If you've ruled out vacuum leaks at all the lines and with smoke/carb cleaner, I'd bet you have a lazy fuel pump or a clogged filter.

[justin85]

Have you replaced the front O2 sensor?

[crash93ssei]

Usually a leaking booster will also lead to a very stiff pedal as well as a hissing sound in the cabin all the time or just when pushing the brake pedal. Just had to replace the booster in my '96 Z71 because it was leaking vacuum, it was fine until I pushed the brake pedal then it would hiss and the pedal was very firm and very poor performing brakes, almost dangerous to drive.

[redzmonte]

i would think if you put small ammount of vac to the system with a gauge it should hold vac.. im sure there is a tool to test vac.. Also you cold try smoking the Booster itself threw the hose.. something like this i assume would work. I am experienceing the same thing you are.. im gunna test fuel pressure here soon and see if i can narrow it down. I found my vac block leaking where the booster hose connects to the intake, hose clamped it and my fuel trims improved but still comes on with a P0171

[Mechanical Mike]

I've only had one car with a bad booster & it's just like Crash said. You'll hear hissing in the cabin & the pedal will have a stiffer feel. Mine only seemed to leak when the pedal was pressed & it kind of felt like the pedal was pushing back when it started leaking.

You need to get a scanner on the car & check the long & short term fuel trims at idle & again at around 2,000 - 2,500 rpm. Just might as well get the MAF sensor readings at the same time.

[Oldman]

Thanks for the help guys.
Fridge, to answer your question, I have checked the fuel pressure and I have 48 psi at idle. I have submitted a post asking exactly how to test the fuel pressure since some posts state that an idle test is not sufficient. I know that there are other tests that need to be preformed, but I'm not sure what they are.

Thanks,

[Jfridge92]

You're correct that the idle test isn't complete. Sometimes a fuel pump can be great at idle, but once it's under a load it can start to fail. You really need to be able to drive the car at speed and WOT with the fuel pressure gauge hooked up and see what's going on, or like others stated, get a scanner on it and see what your short term and long term fuel trims are doing. MAF data can help as well.