93 XJ6 VDP Dangerous redline on Cold Start
 

So I just finished doing a Head Gasket on my 93 VDP. Everything is put together and it starts. But when it starts without touching the pedal it bounces on the redline. Before it redlines, I shut it off to prevent engine failure. Ive been trying to troubleshoot but havent figured it out. I wanna get my car running asap. Does anyone have any advice on this???

Sounds like your throttle is wide open or the throttle position sensor is stuck in the "full on" or wide open throttle position.

Hi AbstractCustoms,

Welcome to the Jaguar Forums! It's great to have you with us.


Thinking out loud with a tired brain:

Was the throttle return spring reinstalled correctly? If it is unattached or attached to the wrong point the throttle might be wide open as Larry noted.

Is there an air leak somewhere between the MAF sensor and the intake manifold gasket? For example, if the hose clamp is overtightened where the air intake elbow attaches to the accordion hose that leads to the throttle body, the underside of the elbow can collapse inward, creating an air leak that can't be seen from above.

Were the EGR pipe and carbon canister purge valve hose properly reconnected to the port on the underside of the intake manifold?

Are any crankcase breather hoses cracked, or any vacuum hoses detached?

Did you use a new intake manifold gasket and were the screws and nuts properly torqued? The torque spec is fairly low, and overtightening the fasteners can crack the plastic core in the gasket.

One thing you might do is check the Vehicle Condition Monitor (VCM) for any stored Diagnostic Trouble Codes (DTCs) that may help narrow down the diagnosis.

Hopefully other members will have additional ideas.

In the meantime, please visit the New Member Area - Intro a MUST and post a required introduction so we can learn something about you and your Jaguar and give you a proper welcome.

Cheers,

Don