rd70

i have an 85 vette when cold idles high and stalls when trying to accelerate. what may cause these issues?

gerardvg

Hi

Usually a vacuum leak or intake runner gasket leak can cause a high idle, The IAC valve can cause this also.

Check the vacuum hoses for fuel from fuel pressure regulator, in case the diaphragm is torn..

Check the IAC valve is secure (the valve on inlet manifold below TPS sensor) it has a 4 wire square plug if it gets loose will allow a vacuum leak and suck air in raising the idle.

The EGR exhaust gas re circulation valve can jam and not fully close cause rough idle or stalling.

Check all the wiring plugs are connected correctly to the MAF, TPS, IAC
do you have any check engine codes ?

kael

Check some basics too.
Fuel pressure
Spark plugs and wires, spark at plug
Air filter

Lean fuel might cause high idle.

A Peter C4

Let it warm up.