I have a water-related misfire.

It first happened when I washed the engine compartment for a car show. I was very careful with it...the car sat all night in a dry garage and the next morning, ran like absolute crap for the 15 minute drive there, no SES light. After it sat all day in the hot sun it was fine.

Today it was pouring like crazy, horrible, horrible shaking-like-a-*****-in-church misfire. Flashing SES light and all (multiple cylinder misfire obviously).

When I got home I popped the hood and looked for something obvious, it appears nothing is getting wet, every piece of the ignition system was dry...there was a small bit of water puddled around the fuel injectors but that should be of no concern, correct?

Anyone else have this problem? Only when it rains.

My car -->> airlid/headers/ls6intake/ORY/catback car.

 

I also have this problem. After much work and many new parts I've just decided to make sure I never get caught out in the rain. Just for reference I put on new plugs and wires with the problem occuring before doing my major engine work. I've also tested each coil on it's own as well. My only suggestion is to take a squirt bottle of water and start hitting stuff until you find where the problem is. Myself I've been working on this for over a year and still havn't figured it out. Let me know if you or anyone else figures this out.

 

Exact same problem. I have checked for arcing somewhere in the ignition, but could not find anything. I thought at first that it was the ghetto fabulous wiring extensions that I did for the front O2's but I'm not getting any O2 codes, just that god awful P0300, no other codes. And it only happens when it rains, which here in Central Florida is every damn day. I have no clue what causes this problem, but I have this problem with my car and so does my friend who has the same header/exhaust mods I do. I would love to solve this as he has other vehicles to drive, but with a motorcycle and a car that barely runs in the rain Central Florida is a crappy wet place to live for between 6 to 9 months a year.

Abe

 

I believe it may be 02 related. The car drives fine for the first couple minutes (open loop) but as soon as it hits closed loop, the trouble begins. Monitoring the 02s showed that the passenger side sensor is not moving at all like it should...going to get another one and try it.

 

Might work....keep us posted!

 

OK Kelly, 2 questions. Did you actually pull codes? I'm assuming you did, and got P0300 (random miss) like me. Any 02 codes? Wouldn't you throw some O2 codes if you had an 02 mis?

2nd ?: I have similar setup setup to you, do you know if rear 02's are same/interchangeable with front 02's? Because I still have my rear 02's (catalyst monitors) and was wondering if they are the same.

Lemme know what up.

Abe

 

This may sound silly- but how long did it run for?
You might have residual water in the manifold or air intake tract somewhere.

Make sure no electronics were damaged.

In all honesty, if it were my car, I would replace the plugs and wires as a start.

 

The problem is not only just after a wash, but also in the rain. In addition, I for one have already replaced my plugs and wires more than once to no avail. Thanks for the thoughts though.

 

I am positive it is an o2. I flashed the car to stay in open loop until I could get a sensor, and it has run without any issue since then. The vette 02's from the dealership are $120 my cost, which is too much $$. The bosch ones are $70 @ advance auto but people say they suck bad...I am just going to take one of my stock rear 02's and extend the harness so that I may use that 02 once again.

 

See I was also running fine at WOT, which led me to believe it was an O2 issue on my car as well, but I didn't get any O2 codes and I don't have a scanner, just the chump down at the local AutoZone to pull codes for me. My thoughts were also to use my rear O2s and extend the harnesses (maybe doing a less ghetto fabulous job this time) but I am very lazy.

Please please please let me know if this solves your problem. I would love to be done with this crappy problem. Thanks.

Abe

 

I will let you know Abe, I've just been dragging *** about fixing it because I've been so busy at work...and the last thing I want to do after fixing cars all day is fix my own. An o2 problem will disapear at WOT because the computer ignores the sensors and dumps fuel into the car.

 

Yeah I know what you mean about working on your car after turning wrenches all day Kelly.

Anyway, the whole reason this problem we're having is driving me nuts is that the car runs fine at WOT when it's misfiring at partial throttle or idle. Which obviously points to an O2 problem! But no damn O2 codes! And a P0300 Random Mis code! What the hell is that supposed to mean? I mean it runs fine at WOT, so that tells me the ignition is working fine, the fuel delivery is there cause it runs just as strong at WOT as it always has, I can't find any arcing and the plugs look like they have less than 10K miles on them, because they do. AAAARRRRRGGGGGHHHHHHH!!!!!

Well that's enough venting. As far as the Bosch O2 sensors go, I've never had any problems with them on any customer's vehicles I've put them on at my old job, and from what I've seen with a couple friends with more miles on their LS1's than me, the OE ones suck ***. I was under the impression that the O2 sensors on these cars are somewhat notorious for going bad, whether on stock or unmodified cars....

Maybe tomorrow I'll stop being lazy and jack my car up and crawl under there to try and switch those sensors out. Do you know for sure that the front and rear O2s are the same parts? I am once again lazy and haven't bothered to research the part #'s or check visually to see if they're the same. I guess let me know if you make any progress and I'll post back if I get not lazy. Thanks.

Abe

 

I suppose that when an o2 begins to fail, it does not necessarily set a code right away, but can send your driveability to the ****ter. I have fixed cars like this at work as well (Dodges, but same idea where there is no o2 code, just a misfire). A random misfire 0300 could be from anything...I just figured that since my o2 was hanging low when I looked @ it with the scan tool, that the car was just dumping fuel into it, making for a horrible idle/slow driving around town. Since the o2 hadn't failed enough (yet) to set an o2 code, it went with the next best applicable thing which would be a random misfire. If you don't have a specific misfire code (i.e. cylinder 1 etc) then I wouldn't worry about the ignition too much if you know that it is good...

Try swapping o2s. They have the same part number, they have to be the same thing. After all if fronts weren't the same as rears, then I would imagine people would not use the rear vette o2 sensors as front o2 extensions for header cars like they do.