Dear Steve,

Good p.m. and may this find you well. Cost-free, quick things to try:

(a) Wiggle the wire that runs to the RPM/Crank sensor. This sensor sits atop the tranny bell housing, at the 10 o'clock position, when you face the engine. If engine performance varies, when you wiggle the wire, that is a sign of a failing sensor. Usually, when the sensor fails or "goes bad", the engine simply stops. However, if a wire insulation failure is producing an intermittent or weak short to live, it might produce inconsistent engine operation.

The wire runs straight down from a connector on the center of the firewall, just above the engine. The connector is below a harness, covered in a ridged plastic coating.

(b) the constant idle motor might be dirty. It is located on a bracket, next to the intake manifold (driver's side of the engine, US/Canada models). See the FAQs under FEATURES, above, for the cleaning procedure.

(c) the fuel injection relay (radio interference suppression relay) is located in the engine bay, next to the power steering fluid reservoir (for turbo models). This relay should interchange with the cooling fan relay. If the fuel injection relay supplies power to the injectors. If it is failing, fuel delivery to the cylinders will be inadequate, even though the fuel pump, fuel regulator, and throttle are all working 100%. If taking the cooling fan relay and putting it in place of the fuel injection relay produces an improvement, then you've found the problem.

There are other things to check, but you'll need to get "analytical parts", i.e., spare parts that definitely work, even if used.

Hope some of this steers you in the right direction.

Yours faithfully,

spook