"CHECK ENGINE" light came on---why?

[trshman]

I bought a '98 Exped XLT/ 2wheel drive last Sept. One owner, 93K on it, Carfax gave it a clean bill of health. Car's in great shape. My mechanic checked it out; only thing he said it needed were upper & lower ball joints which I replaced along with an oil change and filter for the tranny. Cars been running GREAT, VERY happy with it.......until
Last month I got delivery of my Griot's engine cleaner. Took it to the do it yourself car wash, sprayed on the cleaner, let it soak then sprayed down the engine, gave it a good soaking.

Within minutes after leaving she began to misfire and the "check engine" light came on; felt like it was running on 4 cylinders. I figured I got something wet, kept driving and sure enough about 15 minutes later she began to run normally again. Haven't had a problem again, until today.

Went to the do it yourself car wash again. This time I didn't pop the hood and wet down the engine, just washed off the dust with straight clean high pressure water.

About half an hour after leaving the "check engine" light came on and she started running as if she was firing on 4 cylinders. It eventually cleared up.

Any ideas or suggestions as to what I should check to find the cause ?

Thanks in advance, Bob

[alloro]

Which engine?

[projectSHO89]

#1: QUIT WASHING THE ENGINE!!! (Caps intentional).

You are getting water down in the plug wells and are shorting out the spark.

You may need to pull the COP (or wires) and blow out the cylinders.

Steve

[Gevans17]

beginning to see a pattern here?

[AtlPikMan]

My guess would be Warter on the Plugs......

[JLMoreno911]

if you guys read his post...he only washed the engine once...the last one was just a car wash...

you might be getting water into the air intake if it did that even when you didnt open the hood...
next time you give it a wash you should pop the hood when your done to see what is getting wet...
like previously stated check plugs...distributer [if any], air filter...good luck finding the problem...

[trshman]

Howdy folks, thanks for the replies.

1. it's the big engine 5.4L
2. I didn't pop the hood and spray inside the engine compartment yesterday but I did spray into the vents at the base of the windshield.

I mention this because when I cleaned the engine last month I noticed what looks like a black plastic cover on the firewall / passenger side just below the vents.
I remember spraying that sucker pretty good and am wondering if it conceals any electrical connections I might have shorted.

Bob

[alloro]

The main battery power and fuses and all of the engine control wiring the goes to the computer is behind that cover.

[trshman]

alloro,
all the control wiring and fuses eh. well that sure sounds like a possibility to me

I'm a little concerned that I could cause the problem with the hood closed. With the rainy season upon us here in S. Florida I'm a little concerned if I'm going to have problems during the heavy rains this place is famous for.

I'm going to take a closer look at it and see if there's something I can do to protect it a little better.

Thank you and everyone else for your input.
Hope I can return the favor. Have a good one, Bob

[sbclemens]

Originally Posted by projectSHO89

You may need to pull the COP (or wires) and blow out the cylinders.

Steve

Pull the boots and use dielectric grease on them. If the boots aren't protected even high humidity can cause a short.