Throttle sticking, Seeking advice for sticking throttle Options

[turtleman]

I am a new owner of a Porsche 914 1.8L . The engine has been running strong since I purchased this car about a month ago. Then one day after driving it an hour from my home it started misbehaving on my return trip after 15 minutes of the 60 minute drive back. The throttle seemed to stick and remain at the last RPM level. (sort of licke cruise control when you do not want it!) If I blipped the gas pedal, the rpm's still would remain at the higher level. I recall the rpm's would increase even further if I had it in neutral or the clutch in.

I replaced the accelerator cable, and by the looks of it, one would have thought it definitely was my problem. However, the condition persists. I then removed the throttle body and cleaned it thoroughly. After replacingf it and trying it again the high rpm's remained.

I then took a closer look at the Haynes manual and noted that their was a spring that went from the upper lever on the throttle body toward the rear 'firewall' lip between engine bay and rear trunk. I am missing that spring, so I tried to firmly push the upper lever away from the direction that the accelerator cable would pull the lower lever if one were to depress the gas pedal. When I pushed the upper lever there was no effect on the rpm's. When I pushed the lower lever in this manner this seemed to lower the rpm's, howver, it only lowered them a little.

I had been advised that my problem could be: (1) advanced timing (But would the timing actually slip/retard while driving?); (2) vacumn leaks before or after the throttle body; (3) the decel valve and/or the air regulator

I am totally inept in diagnosing and would appreciate any suggestions on how to
isolate these factors and test for each separately; ie. how do I check for vacumn leaks? how do I check the air regulator?, the decel valve?

I appreciate any advice and any further suggestions on other potential causes for this problem.

If I can not fix it myself I will have my mechanic check it out however, I would prefer to learn myself in case I get stranded in the future. Also my mechanis is booked and I want to be on the road!

Thanks in advance for any advice and your patience with a novice.

Chip