Thanks to the guys at Jag-Aire, we may have made a breakthrough in trying to figure out the non-operational HVAC issue in my '87 XJ6. However, we may have stumbled upon a larger problem.

David Crosby at Jag-Aire advised me to inspect my vacuum canister for rust or punctures. While the canister looks to be in fine shape, one of (or the only) main vacuum lines simply plugs into nothing. There's a vacuum hose with a white stripe that goes behind the engine and it's just completely disconnected. If this hose used to go to the heater core valve, I can explain it, as that valve has been removed from this car and a spigot-type valve installed so that we can manually close off or open up the heater core. However, if other things run off that same vacuum line, we have trouble.

This car has already been upgraded to a modern PCV valve rather than factory-style breather system at the top front of the motor, so now we're into comparing new vacuum lines to old ones and trying to figure out what we're missing. Given that David believes we have no vacuum coming into the cabin at all (I agree with this assessment), I'm betting it has something to do with that hose.

Also, in the last week or so, I'm not running pig-rich with a raw or half-burned fuel smell. There are no obvious leaks. But on a highway trip I usually get 23-25 mpg on today, I got 13. It also has a rough idle. The reason I think these issues may be somewhat connected is that this car has always been notoriously hard to start but once it gets started and warmed a bit, it picks up a smooth idle and then runs for as long as you want it to. We've replaced all injectors, all fuel hoses, fuel filters, spark plugs, plug wires, you name it. Now I'm wondering if there isn't some kind of vacuum issue afoot.

I guess I need an underhood vacuum diagram if anyone has access to one of those, and your take on these problems and whether you think there's a connection.

Jess

 

you can download vacuum diagrams from my website:

https://jagupgrades.webstarts.com