Ignition Miss When Cold???

[Roger924S]

Hey guys, We just added a one owner 88 924S to the Garage. Same Color & Interior as the one we have had for 13 years. It has 90,000 miles. Any when it's cold it has a miss between idle & 2500 RPM, then it smooth out. After it warms up it doesn't seem to be noticeable. I checked the ignition wires, changed plugs, checked to see if injector are firing, checked cap & rotor, checked clamps and vacuum lines. I'm puzzled, any suggestions.

[SoCal Driver]

How cold? Check the clearence on the sensors.

[Roger924S]

It generally misses or runs uneven until the engine is at operating temp, it doesn't miss at idle and after 2500 RPM. It seems to smooth out after 2500 RPM with sudden boost of power. It still feels a bit uneven at operating temp, but not as bad same when it cold. Are you thinking the timing sensor gap is off a bit. It definitely feel fuel or ignition related.

[SoCal Driver]

A bad pressure regulator will allow too much fuel and in some cases over pressure the injectors so they do not open.

Ignition system can be compromised by old wires, rotor and cap. Usually not so temp related. Replace with stock. You can replace just the wires with a little work. Cheaper than the cost of a full set.

Vacuum leaks can cause problems. Check the rubber boot between the AFS and the throttle body for cracks and not seating. Even the small diameter tubing that controls the fuel pressure regulator and damper can have cracks in both the rubber fittings and the tubing. Also seen the intake manifold being loose at one of the runners. Usually due to a stripped bolt.