Rough idle when wet...

[vwtipeii]

Hello all! I have washed my engine compartment a few times now after wheeling. After each time my yj has a hard time starting for a day nor two after, then once running the idle is extremely rough. The idle sits around 300 rpm (very low) and the engine almost stalls if I add any skinny pedal at all. Once things get a bit better I can get maybe 1500 rpm but the engine sputters and drops rpm If I add more throttle. Sputter sputter... Rumble rumble backfire. I assume it is something with water and electrical connections w sensors of some sort. Any ideas? Any recommendations how to diagnose and isolate the problem?

Thanks,B

[aw12345]

Start with sparkplug wires cap and rotor, you can even narrow down the diagnosis with a spray bottle with water in it, run engine spray sparkplug wires and distributor cap and see if it start acting up, if so replace

[Tumbleweed13]

Stop washing your engine.

[Jeeperator]

wd40=Water displacer formula 40. most likely wet wires or moisture in the cap.

[6spdYJ]

If water gets in the Throttle Position Sensor it will act goofy. See post #3.

[vwtipeii]

I don't think it is the wires or cap, but I will check. I put on one of the DUI performance distributors with the "screamin deamon" coil about 6 months ago so that should all be fine. I am hoping it is the maybe a TPS that is about 15 years old.

[Jeeperator]

Water is any ignition systems enemy I dont care what ignition system you got. Btw split fire plugs dont do shit either lol. Tps is also a good thing to check but if its missfiring its ignition related. A little bit of moisture like a few droplets can cause missfire.

[brokenujoint]

1. shopVac blowing air OUT. put it in your tailpipe(the jeeps not YOURS) and blow air into the system with out running the engine. Now spray soapy water where your manifolds join the head. Also check the exhaust for cracks.
2.. pop off your intake filter/pipe to TB so you expose your throttle body. have someone put the same shopVac to your intake BUT dont snug it up. you want the air going into it to not be so aggressive. if you have a house vacuum cleaner than can blow air use that instead or even better yet a air hose with only about 20 lbs or less of air. check intake for leaks.
3. If your inclined, pull off your fan from your fanclutch. run your engine and check with the same soap mix , your ignition system including wires, plugs and distributor. your not looking for bubbles your looking for a change in idle. also check all of your vacuum hoses. DONT run your engine for to long because no fan= overheating.
I'm pretty sure with these methods you'll find your leak!
Good luck.
PS I wrote this thing THREE times. Each time I somehow hit some button and it blew everything out. So Appreciate it sucka!

[Jerry Bransford]

I'm betting your ignition wiring insulation has just gotten old enough that when it gets wet, it is allowing the spark to arc through it to the block or other metallic items near the wires. Carry your old OE ignition coil as a spare for that "Screaming Demon" ignition coil, mine crapped out on the trail and I had to borrow an ignition coil from someone who happened to have one. Having one owned a Screaming Demon coil, save your $$$ and stay with the OE coil which is better made and far more reliable.

And if you do replace your ignition wiring, ignore the mostly junk ignition wiring sets at your auto parts store and install the OE wiring from the dealer. Most of the wiring sets sold in the auto parts stores, particularly the ones that scream "Low Resistance", are mostly junk that will cause interference with your AM or CB radio or the engine computer. Not to mention many aftermarket ignition wiring sets are so poorly constructed that they pull apart the first time you replace your spark plugs.

[brokenujoint]

Ive learned lessons over the yrs. I'm no geezer but I'm pushing 40 and have been jeeping for 25 yrs. What I've learned is not to mess with stuff under the hood. Build your axles to the TILL, but stuff like plugs, wires, starters, valve train, oil pumps, clutches... all that stuff.. keep it dealer OEM.. My 97 TJ with 126,000 miles is running STRONG and its still got the original plug wires and distributor. Sadly I have to admit I have a new distributor cap... lol... no cracked headers, no electrical issues.. nothing.

My 1st jeep I had I bought a holley carb, (GARBAGE), mallory ignition system for like 450.00.. garbage. all this summit racing stuff... waste of time and money.
As Jerry stated and it cant be overstated.. when you find the problem replace it with dealer oem. It cost a little more but its WAY worth it. Stay away from all of those Vato-zone, Pep-boys garbage.

[aw12345]

Yup most of the Racer Brown aftermarket crap isn't worth the packaging it comes in. For reliability go for oem engine and ignition parts

[Lumpy Grits]

Water is a conductor.....If your SP wires are more than a couple of years old replace them. Wet wire(s) could be arcing to the block.
Get the best wires that NAPA has. Stay away from cheap chain store crap.
Also, you could have condensation forming under your "dizzy" cap. Causing a cross-fire with in the cap.
Back off on hosing the eng. down to maybe twice a year. Blow the dust off with an air compressor.
Cheers,
LG

[vwtipeii]

Thanks for the feedback. The wires are brand new and they are pretty beefy. They are the http://www.performancedistributors.com/jeep4.0.htm. I can't remember if the Jeep did the same thing before I put on the new cap/rotor/coil. I am running regular oem plugs. I think it is the TPS or the wires that go to it. I will play around with the shop vac in the next few days

[Lumpy Grits]

Go back and re-install the OEM ing. parts and see if there is a change with a wet engine.
LG

[aw12345]

I would go with my original advice get a spray bottle, fill with water, idle engine, preferably in the dark and spray away till it starts running crappy., You see sparks of any ignition part then you know what to do. If a TPS fails due to water it's generally toast. In other words it doesn't fix it self