excessive revs with hot engine

[Flyair]

Although the renovation of my Pagoda is not yet fully done, the car is already looking great and - in principle - mechanically sound, just in need of some fine-tuning. The car run well enough to allow me for checking in the 2nd Polish Pagoda owners gathering last Saturday. At least that was the plan. The reality turned to be less rosy.

Here is what happened:
After starting the car and driving for about two kilometers, I noticed that the engine revs don’t decrease when I release the pedal. What's worse, driving further I noticed that the revs grew till about 5000/min and the efficiency of the brake system was already at the limit of safety. After stopping the car, I opened the hood and saw that the throttle rods do not return to the starting position at idle. I also noticed that it occurs only when the engine is hot. After it cooled down, the system operated normally again, i.e. the springs were capable of moving the rods back in the initial position and the revs returned to about 800/min in idle.

Adjusting the springs did not help. I just hope it's not the FI pump. My mechanic said that this problem is beyond his capabilities, so from Monday I'll have to look for a specialist in these matters  :'( :'( :'(

[wwheeler]

The linkage system is quite complex and has many areas that could tighten up with heat. I would say the first step would be to lube ALL pivots. That would include linkage ball sockets, rod shaft bearings/bushings. Be sure to look at the pivot just below the exhaust manifold on the right side of the engine block. The other place could be the Venturi flap (air intake) could be binding. There are also aluminum bearing blocks along the firewall that could bind. The last and worse place to bind would be the IP. Not sure why that would bind with heat unless the oiling wasn't sufficient.

I lube my linkage system at least every year. I use a small needle point oiler with motor oil. You should also check all fasteners and make sure they are all tight.

Others may have suggestions.   

[w113dude]

Maybe throttle body is sticking in open position when hot.

[ja17]

Hello,

First dis-connect the linkages to isolate the problem.  Find which component is the problem. 

Most likely is the pivot on the block under the intake manifold.

[Flyair]

Joe, Shaun and Wallace,

many thanks for your kind advices. I will start checking on that and hopefully report on both the issue and its solution as soon as it is over

[stickandrudderman]

First dis-connect the linkages to isolate the problem.  Find which component is the problem. 

Most likely is the pivot on the block under the intake manifold.

Seconded.

[Flyair]

Stick,

Thanks for the opinion. I am going to meet the mechanic today and remain optimistic so far that soon it will be fit and running as it should 

[Flyair]

Your advice was spot on. The linkage was blocked exactly as you said, so after greasing and enlarging one rubber sleeve under the manifold block, things went back in order and the engine works perfectly well (I should like to think: better than new )

As I think about it, based on this and many other cases, some of you guys should be able to conduct Pagoda e-learning courses, or even better a e-restoration and repair shop, advising and monitoring simple mechanics online worldwide .
 
Anyways, thank you very much again for good guidelines.