Would these exhaust leaks cause my trucks RPMs to go from 550-650 after warm up?

Speaking of stink: Decades ago I was changing some ancient diff oil (hypoid) and my wife decided to visit the garage. To this day she wants to barf just from me reminding her. That is some serious stank.

 

I use a scan gauge for coolant temps and rpms due to my truck not have a tach. The truck starts awesome it’s after it’s fully warmed up (188-190) that it’s starts having a small jitter. At the light I see my rpms go down to 550 and fluctuate to 650 max. Park its 700ish. I turn on the ac and the it tends to balance out making the truck run smoother. I can hear the cat rattle a bit and a bit of air coming out from where the gaskets go and side of the cat. Not sure if that’s relevant.

 

just changed my rear differential oil due to a flood and hoo wee. I’d rather smell pb all day. Lol

 

Yep. I remember ages ago when a friend bought some old crapped out 50's era truck. The smell of its 50 year old gear oil hung around the garage for a month. Smelled like death. I feel like I can taste it while remembering.

 

Reminds me of old supercharger oil….ugh

 

Sounds like vacuum leaks. Smoke it. It only takes a few small vacuum leaks before these engines idle like crap. And you can get a really capable smoker from Amazon for under $100. It's a hell of a diagnostic tool.

 

You can either squeeze off the vacuum line from the brake booster to the intake manifold or disconnect and plug it to see if the idle improves.

If you can slide the throttle shaft back and forth or up and down even a little bit the idle will fluctuate.

 

How do your long term fuel trims look? Your engine probably having a hell of a time burning all that extra fuel. The first thing I'd do is fix all those exhaust leaks 100% and get your long term fuel trims in spec. You may have more than one problem causing this but the leaks have to be fixed no matter what. You already smoked the intake so you can pretty much rule that out.

 

gear oil IS THE WORST
Auto diff or lower unit from boats
IMO…..3 days minimum to get rid of the stank from your hands