Contour Enthusiasts Group Archives Forums General Troubleshooting Washed engine, now car won't stay running

ContoursKickAss,
I've washed my SVT's engine several times, just last Saturday in fact, & have not had any starting or running problems.

As ScottK & el contouro mentioned, the most likely culprit is moisture inside an electrical connector or device.
I assume you used a high-pressure water wand or similar apparatus to clean your engine, hence the likelihood of moisture penetration is increased compared to just using a garden hose as I do.

Another possibility is the high-pressure may have caused a vacuum or other hose to become loose which may create some kind of air leak that your EEC computer is attempting to compensate but does not show up as a trouble code.

I had this happen on my Saleen Mustang one time when for some inexplicable reason it would not maintain a steady idle & would constantly stall.
After several agonizing attempts to isolate the cause, I finally traced it to a flexible connector between my supercharger's discharge tube & the throttle body inlet. There was just enough of a mismatch between the two that it wasn't readily apparent to a cursory inspection, but it was enough to allow the pressurized air to escape, causing the computer to go a bit zany.
Once I realigned the connector & tightened it, the idle returned to normal.

I'd suggest looking closely under your hood for loose connectors, hoses & any residual moisture.