When I depress the accelerator it travels 2" before I get any response and then it's VERY sensitive. It's hard to keep it at a constant speed. Any ideas?

I only have 123 Experience. On mine if you trace forward of the Bell Crank that is on the Fire Wall there is a Rod that goes to the Linkage and on it is a piece of metal with a Kidney Slot and a Bolt with a 10mm head to make an adjustment there.

Also the Plastic Ball behind the Bell Crank that is the Bushing wears and the plastic can fall apart.
So it may be you just need to find out what is now worn out.

In the 123 Manual they show the 3 different types of linkage setups and they give the stock lengths of all of the adjustable Linkage Rods; so the real manual for your year and model would be handy to have.

If none of the above is applicable it could be some issue with the IP.

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84 300D, 82 Volvo 244Gl Diesel