having trouble tuning carby have workshop manual says look up tuning info on under bonnet decal have reset carb to factory specs fast idles at 1600.in drive 600rpms.after warm up still idles at 1600 am missing under bonnet decal decal for tuning can any body give me tuning details

I really don't think you will find any specific tuning info under any bonnet. Usually the only thing on any decal is info for where the timing and idle should be set before and after warm up. There may also be info for routing the belts, and how the emissions systems should be hooked up and that is about it.

If your needing to tune your carburetor I would look for a local shop to lend you a hand. I have never had any luck tuning a Q-jet.

Check and make sure the secondary throttle plates are closing all of the way. Sometimes they stick open a bit and ruin the idle. Check this first.

The fast idle adjustment is on a cam on the passenger side of the carb. The 1600 is usually on the next to highest step of the cam, with the car warm.

You want to set normal (curb) idle before the fast idle, or the adjustment will be off a bit.

Thanks AFTER SHARK and kysters for replies problem now with ERG system have broken ERG TVS sensor.Have got replacement.Canany body give me detailed diagram of ERG hose routing for 80LG4 notin workshop manuel if possible which hose goes where from air diverter to ERG TVS and EFE TVS top in bottom out or vise versa.problem is car fast idles ok then idles ok but soon as you put it in gear car stalls. its auto any help greatly appreciated.

hmmm, Every car that I have owned that would run fine out of gear and then die when put in gear I could usually track to a Vacuum Leak. Most of those have been on the intake manifold, but on a c3 and their complicated vacuum systems It sounds like a hose might be off.

The EGR is usually supplied by a ported vacuum at the passanger side front of the carb. This is toward the bottom of the carb. It goes to a TVS, thermo vacuum switch, which will only allow vacuum when the engine is warm, and then goes to the EGR valve.

A constant manifold vacuum supplies both the EFE, Early Fuel Evaporation valve, and the intake air temp control or THERMAC, therostaticly controlled air cleaner assy. (I think I spelled that wrong)

The THERMAC uses the manifold vac from the carb to the control valve on the air cleaner, and then to the air inlet blend door motor. (Vacuum motor)

The EFE or vacuum controlled heat riser, used manifold vacuum to a TVS that only opens cold. This could be a multiple port TVS shared with the EGR, or a seperate one. With vacuum applied to the EFR motor, the flap closes. With warm engine or heavy acelleration, the vacuum is gone and the flap opens.

im not very good on this computer stuff but thanks for your input After Shark(I spoonted on your car) great pics and kysters for info but replaced carb with holley 600 purrs like a kitten drives like a charm smiling and waving again.

I'm glad to here that you are back up and running. I have seen old carbs that would appear to be fine, but would have a vacuum leak on a metering gasket, which would actually be a vacuum leak messing with the fuel mixture causing sparatic idle and driveability issues. Metal tends to warp due to age and cause metal surfaces even with gaskets not to seal correctly and with a some time and effort to straighten those surfaces the problem would go away.

Doesn't matter what brand of carb you have its just nature of the beast.

Thank you for the compliments.