Bought this car a month or so ago. 

1999 Honda Odyssey Automatic 3.5

170k miles

Have done a tune up, replaced spark plugs, coil packs, oil, trans fluid, a couple trans solenoids, timing belt, water pump, motor mount, etc

It has no cat converter, a shop installed a straight pipe

i get a code for o2 sensor but also for p0401 and often my cheap Walmart reader says p0401 with a p on the right, like shows code twice sometimes with one having a P on the right. Wtf

Anyways for a few weeks now, sometimes the car has a hard time initially starting. Like if it sits for a few hours and you try to start it, You may just have to try several times while also hitting the gas pedal for it to eventually start. 

if you drive it for a while and restart it usually it will start right up, but also sometimes may have hard time starting.

Has new battery, and battery connections are new and are fine. 

I attempted to start yesterday morning, and it would like start but bearly and would sound like shit and may hear a knock or two then shuts off, did that like twice. But hasn’t happened since, and has been starting fine for hours now. Been driving all day. Don’t hear any unusual engine sounds at all.

I see code p0401 is for something EGR related.

Backyard mechanic replaced waterpump timing belt and ever since my heater isn’t working along with the heater and ac controls they don’t even turn on.

van runs well, compression test few weeks ago showed good. Trans doesn’t slip, shifts smooth.