I recently drove through a deep puddle in which water rushed over the entire front end of the truck. Afterwards, the engine idled rough and shook. I also noticed a loud knock. I replaced the spark plugs, spark plug wires, and air filter. However, the knock is still persistent. The truck is a 1994 XLT model and has a V-6 and distributor ignition. Does anyone have an idea as to what is causing the knock? I appreciate any input. Thanks!

 

It sounds like you hydro-locked the engine and damaged something internally. :-( You might have a bend rod or a bent valve.

 

This is what i was thinking too, but to be on the optimistic side you could have just ruined a sensor.

How long has it been doing this?

 

The knock was noticeable after having drove through the puddle.

 

yep, you definantly have a bent rod.......My friend and i were driving an 02' ranger (4 cylinder) and were going through some deep puddles,the last one we through stalled the engine......it was hard to crank back, and when it did it started knocking.....about 500 miles later it threw a rod out the side of the engine block, so there you have it

 

Wow, that is about the biggest NO-NO in off-roading. NEVER EVER start an engine right after it stalls in a deep water puddle!!! Or you'll end up like Brandon_man. Big problems. For future refernece, if you ever go through a puddle, and your truck dies, DO NOT TRY TO RESTART! Now, its time to get wet.....get out and if you have a buddy around (which you should), have him tow strap the truck out of the water. Next, pop the hood and remove all the spark plugs. After you have removed them, with them still out, get in the truck and crank it over for a little bit. This will evacuate all, or at least a majority, of the water out of the cylinders. Next, reinstall the plugs. Now, you can restart. But keep in mind, the damage may have already been done when the truck stalled. This is just in case it does happen, you might be able to save it.

I'll tell you what, I've never seen anything kill more trucks off raod, than people driving through water that is too deep, going too fast. It may look cool, but it is way more problematic than it's worth. If you HAVE to go through deep water, make sure it is at a very very slow pace. And if it going to be bumper height or more, just find a different path. It'll save you a lot of problems on down the road.

 

Had three people this year bring in subcompacts that they did the "cold air mod" by slapping on a k&n and directing it down by the front tires. Since it has been a wet summer they just kept restarting and driving. The Ford Focus was the most graphic, about 4 holes in the engine, and he said "that couldn't have caused it". Missouri roads are not for some mods, any rainy year is pothole puddle season.

 

That's what I'd suspect.
Water in the air intake, into the cylinders = bent connecting rod.

Does it knock at all engine speeds, under all loads, and does the knock speed increase and decrease exactly with the crankshaft RPM?

Is it a little louder while revving up, then while revving down, but still audible at all RPMs? If so, rod knock is indicated.

Get yourself a stethoscope from an auto parts store.

It might be a cracked exhaust manifold, but that wouldn't have stalled the truck in the first place.