I recently changed my CKP to resolve a P0335dtc. But hard starting is still an issue. I have to hold down the accelerator to get it started. Once I put the car in gear I automatically get an engine fault warning but no check engine & no dtc.Now once we're on the highway I get a temporary gear box fault while trying to get up to highway speed. Hard shifting & a grinding/vibrating feel between 60-70mph. and the worst part is random surging & in a few cases powerloss & even engine stalls all while driving at highway speeds #scaryshit! Now again these things happen everyday in several varying combos. Sometimes it shifts up to 70 as smooth as silk but randomly surges & jerks at that speed. Its a 97 with only a small oil leak off the left valve cover. No dtcs. What the hell kinda demon am I dtiving?

 

if you get a gearbox fault, there will and should be a stored code. Random surging could be either fuel or air problems...easy to diagnose with a code reader/scanner hooked up and you watching real time air, fuel, and those trim readings...along with engine load.

The demon sounds like it has multiple problems...making it more difficult to diagnose the individual issues. Start with one at a time, diagnose for what you know you are capable.

 

My guess is you have the two most common issues on the early XK8. First you have throttle body issues. Might just need a good clean but quite likely that the sensor is on its way out and you will need a new one. Secondly the ZF five speed box may have never had an oil change, it might help if it has one but the symptoms point to possible clutch pack failure

 

As Matt says - sounds like fuel to me.
If you don't have an OBD reader that can do real time stuff start by measuring fuel rail pressure at the Schrader valve
JagRepair.com - Jaguar Repair Information Resource

 

I think I hear a hissing around the throttle body while idling.How do I correct?

 

A smoke test would be the right thing to do, provided you have the tools and know how.
Do you have access to a scan tool to check fuel trim?
If no to either, try spraying the area with soapy water while its running and see if it smooths out, you should be able to narrow it down from there.
A couple of common leaks in the back of the engine are the EGR valve bolts coming loose and map sensor hose cracking/or coming off.

 

Update: ok I think I need to do the tranny service. What type of tranny fluid do I need? Does anyone know a good jag mechanic in south florida?