1999 f150 4.6l 5 speed manual transmission 4x4. Just hit 120k owned the truck since it had 70k. I bought the truck a few years ago needing 02 sensors and fuel pressure sensor on top the gas tank. I've been driving it the last few years the only thing I noticed after driving it like this a while mainly was when you first started sometime it would turn over a little longer before it started and sputter a little when it did then clear right up. This evening me and my pap went to go fishing I pushed in the clutch to start it as it went to start at the same time I slipped off the clutch causing it to stall right back out when it did it backfired big time. Now the the brake pedal is stiff as can be. It's backfiring here and there rough idle up down up down spots sputter when you give it gas. It sounds like i blew out the cat or resignator or something towards the back top of the motor possibly intake? The only codes shown are (p0453,p0141,p0155,p0161,p0102,) most of those if not all were already up due to the bad o2 sensors I believe. I looked at the boost the hose coming out of the front is still attached on both ends. Spark plugs are tight. As far as I can tell most the vacuums look good other then the small one going to the black canister box by the battery and one coming off the top the intake to the little black cylinder to the left of the brake booster both of those were old breaks by the way they looked. I know it's a lot to take in any help would be much appreciated thanks.

 

Sounds like you have three problems: 1) brake 2) backfiring 3) O2 sensors

These seem like independent problems to me.

I would try to get the brake problem solved first. You need 100% reliable brakes if you are going to drive it at all. Look through this article and see if any of the conditions relate to your experience

https://mechanicsdiary.com/brake-ped...sh-causes-fix/

 

I never had any issues with the brakes until I went to start the truck it backfired now it's rough idle brake pedal stiff not much pussure flowing through the hose going to the booster I pulled it off and capped it with my thumb. Whatever happened when it backfired is the cause of the rough up down idle, louder engine/exhaust leak and brake booster issues

 

If you believe the engine is the cause of these problems, then a quick easy check is to do a vacuum gauge test on the engine and see what it tells you about the health of the engine. Takes about 5 minutes to do.

Lots of videos on how to do the test and interpret the gauge readings.

Once you have the readings, go from there. If the engine comes back normal, you have eliminated a variable.

 

Sounds like the booster diaphram is bad.

 

x2.

 

Another previous issue I thought of was when my heater/ac is on and my truck was getting under a load it would pull vacuum from my vents to my defrost it sounds like I assumed that was from one of the small 1/8 inch broken hoses by the battery or the dry rotted one coming from the top of the throttle body to the canister to the left of the booster

 

 

It's backfiring through the intake and the engine is a lot louder it sounds like a exhaust leak coming from the left rear part of the engine but the plugs are tight and the exhaust doest seem to be leaking.. thoughts on spraying something to see if there is a hole in the lower intake to suck it up or suggestions?

 

Blew a hole In the Intake for all you big time mechanics