BREAKING THE C5 IN THE DUMBEST WAY PART 2! THIS THING IS STRESSING MA OUT | SUGGESTIONS APPRECIATED!

[@floodx4947]

Compression test first before anything else. Rule out the worst case scenario. If it's not internal, I think some in-depth diag is needed. Need to scope out what the ECM is doing. You have already ruled out all the basics. I would start by looking at what the signal from the 02 sensors look like. And from there, there is a whole slew of sensors that would need to be looked at. 'Something' is obviously not making cyl 6 happy. Crank / Cam position. Injector pulse.

[@TJsVette]

First off, congrats on the new baby! Second, definitely do a compression test on that cylinder. Nothing in oil like water or anything? Could be a head gasket leak? Double check the ECM to make sure connections are nice and dry and no corrosion.

[@NY-DIYMECH]

Maybe do a compression test, along with a leak down test. Oh, as also scope it, just to attempt to eliminate Mechanical failure. Outside of that, start looking more electrical. Maybe take a look at the crank sensor connection? Trying to throw out basics. Hope it helps. Cheers

[@karltuto]

C5 French owner here. - Take a look at your grounds - take a look at your electrical connector, maybe blow some air inside the engine bay - ecu inside the fender is waterproof but maybe take a closer look to the connectors ? - you have fuse box on the passenger side check everything is dry and fuse are okay. Once my water drain got clogged near ecu and water goes everywhere inside. Hope everything will be fixed ! Bon courage !

[@jaredamyjones6431]

2004 Z06 owner, I would start looking at all of the many grounding lugs.

[@dannpd1955]

I think that I would bore scope that cylinder. Another thought is a wet wiring connector on the ECM. Hope that you find your problem. I would like to know what you find.

[@TheSwampDonkey]

2 more things I can think of, take a look at the mass air sensor, blow out any water in the connectors, clean the sensor. Also, disconnect the engine control module. Unplug and make sure no water is in the connectors. Hell, you might just pull it out, let it sit and air out. Due to the location of the ECM, its possible some water got in this connectors. Hopefully you don't need a new one. Good Luck, I know the feeling, back in the day I had a C4 and decided to clean the engine, ya know, typical spray it down with water. Big Mistake. I quickly found out what an opti-spark was and 1000.00 later it was running again. I know the C5Z doesn't have that but point being, I get the feeling of your pride and joy being down.

[@GregorioLonewolf]

This is part 2 and I've seen most all of the other comments so will focus on other possibilities. Oh, 1st I saw someone mention the Throttle Position Sensor and I am not an ASE tech but my experience is that the TPS would make the entire engine run rough or smoothly as it should. Now, I haven't seen any mention of you checking the oil. Is it possible that there is some coolant mixed in? I say this as on my 87 C4 Z51 it ran very similar to what you are saying and I only had 1 cylinder miss fire. Unfortunately it was also cylinder #6. Closer inspection I found a cracked block between 6 & 8. That is the worst case scenario and hopefully not your issue. Trying to cover some outside bases as I'm thinking it's electrical and or a ground some place. It is my hope that it turns out to be something so simple that is causing all this frustration. Simple things are more frustrating to find than big things. Good luck and keep us posted. I, too have a 2003 Z06.

[@jimcear1766]

Oh boy , have I been there too. Chased a CEL light for months on a ferrari 360. It was a simple vacuum leak I caused. I’m hoping you find it is something that simple. Hang in there .

[@Mattschindig]

You said 7 inches of water. So what would be in that vicinity? Connectors, PCM and TAC. I would lift it up and disconnect everything you can and clean all the connectors. Let them dry for a couple days that way you can take care of your other business and let things dry out while you wait.

[@phynixbrd]

Agreed. Pull that passenger side access panel in the wheel well. Its very low and driving in water that high can get in there and drown the computer. And main wire harness.

[@greenscobie86]

Hmm. So a good known wire and coil + new plug didn’t fix it. Is it just throwing a P0306 and nothing else? Can you check misfire counts at idle? If the car didn’t suck up any water I really don’t think it’s a mechanical issue(low compression/valve train problem/etc.) Checking grounds might be another good move along with the harness for injectors/coils.

[@ImBadAtErrrthing]

When you said you looked at the MAF sensor, did you still try to clean it? That might be one of the simple things you might have overlooked because it looked clean. Those things are more sensitive to contamination than SNCOs ego

[@sherryswisher8911]

I think compression too but it would miss at idle. It has to be something under the battery. That water can get in there. I’m thinking ecm. Love. Your videos it really has helped hope my 2 cents starts some paying you back. I got caught in rain in Aug. 2 inches on 30 min. Water was splashing over the front bumper. I worried as the water has to have gotten into that well. I got lucky. Also check the new 02. They can still be bad.

[@joels6736]

For peace of mind run a compression test. Once you've confirmed no water made it into the engine and compression is there, then turn your attention to the wiring/ECU. My guess would be you either shot water on the ECU under the battery, or tsunami'd it under rolling water. The ECU sits very low in the chassis and it's a low car as is. Pull the ECU out and remove the 4 screw side cover. Spray circuit board cleaner all over it and dry it with a blow dryer. Just make sure you don't soak too much heat in one spot for too long with the blow dryer. It's highly unlikely you would reflow solder with just a blow dryer, but better safe then sorry. Report back after.

[@Millertyl]

Pull off the front passenger fender to get a good look at your computer and harnesses under the battery tray. It's located dangerously close to that 7" line and would only takes one short to cause chaos.

[@thereissomecoolstuff]

Sounds like a bent rod. Hoping for the best.

[@NBJeeper1]

TPS? I recall having a similar issue with my Jeep after some deep water/mud crossings. The Trottle Position Sensor had to be replaced.

[@Legobatmanmw3]

Compression test. I’d think you may have a collapsed lifter, broken rocker arm, broken valve spring, bent push rod. Pop that valve cover and take a look.

[@jonranper]

Congratulations on the new baby! With all that you have going on right now the most logical thing to me would be to get the car to a trusted shop so you can get on with your life. If you have time and the tools you might do a compression test followed by a leakdown test of cyl.6 and a known good cylinder for comparison. Many possibilities but you may have damaged a valve.

[@VetOnVettes]

I'm thinking a valve issue as well. I pulled the valve cover this morning & luckily the springs are good. 🤷🏼‍♂️

[@josephberger9441]

You could buy a borescope pull out a plug and look down into the walls to see if they are all right. Those things are not expensive to buy to have.

[@andrewdoman6294]

Check the injectors a poor amount of fuel will make it run like crap I had the same problem on my old 89 Vette couldn’t figure it out until I took it to a Vette specialist and he found it

[@christianleroy-hernandez2437]

Denso’s, AC Delco and NGK are crap 02 sensors on the C5. Use Bosch exclusively. Seen it time and again on multiple C5’s. Still doubt your issue is the 02 sensors though.

[@VentureNW]

I'd lean towards connectors around the ECM - dry dry dry. So much of what is happening is controlled by the computer.

[@adam96blackss]

I would do a compression and a leak down test and go from there. I would do the whole bank for that matter just the compare and contrast. I'm hoping you didn't suck in water hydrolock and bend a rod.

[@TheSwampDonkey]

What about a ground issue? Water got in a place where a ground is, higher up that typically wouldn't see that and its causing some grounding issues?

[@joenarron6067]

Take it to DPS Racing off Indian River Rd. in Chesapeake.. they're pretty sharp and do a ton of fast cars.

[@Torches-n-Tap-Sets]

Bad life timing. Always the way. Nothing new here vs other comments. Verify no hydro damage internally. Refresh grounds and add some No-ox-id to protect them. It is not a cam or crank sensor. Not the chain. I'm sticking with electric as the problem. Something shorted or cooked. Try swapping your #6 coil for another. You might also toss a spare plug in there or wire if you have them. I have too much junk like that kicking around between too many project cars.

[@paulmchenry7426]

I couldn’t tell if you said you swapped the injector or just listened to them. Different but similar - a friend and I chased a misfire on my LT1 C4 (OBD1) to the point that I replaced the optispark and ECU with no luck. Before that work we had listened and confirmed that the injectors were “ticking”. Since we had no idea what to do now we started pulling the connections off the injectors to see if anything would change and as we pulled the connection off the second passenger side cylinder fuel shot straight out at us. It was “injecting” but not into the combustion chamber. Probably not your issue based on the circumstances but maybe swap the injectors and see if the issue follows. Again, you may have done that but I listened a couple times and couldn’t tell if you just listened or actually swapped. Good luck. I really like the C5 content.

[@sugarbea]

a faulty camshaft position sensor might cause this problem.

[@TheSwampDonkey]

Worst case, it could have bent a rod pushing it though the water, keeping the RPM's up. Hopefully not but water could have gotten in for a brief period to do the damage.

[@kimgrigsby3748]

Hey, I have a 2002 c5 and I pulled the inner wheel well off to see what it would look like in there and took some pictures. i have lowered my car about 1in and the measurement to the bottom of my ecm connectors is at 8ins. would you like to see the pictures that I took.

[@autogaragelife]

Always when you are busy! Rest of the time they behave!Is it code P0306 you are getting?

[@VetOnVettes]

Correct

[@autogaragelife]

@@VetOnVettes lots of compression test suggestions already but have you tried swapping the injector over to another cylinder and see if the code changes? (If you have ruled out spark, coil and line already). Hopefully its not something more serious. Take it that you can still feel the misfire and its lumpy? Read an old forum post saying the crank relearn process on a z06 2001 cleared a misfire code but it was for code P0300.

[@bkeato2336]

Unplug your MassAir flow sensor while the car is running. If the car continues running when you unplug the sensor, it’s a bad MAS.

[@ronaldsmith4479]

Stick a timing light on that spark plug wire to make sure it is firing. If not since you have swapped the plug, spark plug wire, & the coil pack, the wire from the ecu to the coil pack might have gotten buggered up or the coil pack ground could be bad.

[@VetOnVettes]

That sounds like a good troubleshooting route. Will probably do this by the weeks end.

[@casualcombine]

Contact cleaner + wire brush on the connector on the coil pack, and the main white coil connector. 100% sounds like an electrical issue, anything mechanical you would see a lot sooner. Maybe fuel pump connector causing is to run at 100% all the time?

[@TerrySagona]

I had a misfire because of a lost ground. Check your grounds.

[@ronaldday4870]

Maybe check your fuel, filter and tank

[@chrispopiel1162]

I don't know if you have the stock air filter on your C5 might want to check the air filter to see if it is wet. This may tell you if it swallowed any water.

[@beerrun1550]

If it idles fine with no miss it’s not mechanical. Mechanical doesn’t care about RPM. Sounds definitely electrical but that could take some digging.

[@VetOnVettes]

Yeah, I'm leaning that way

[@traywarren]

Check timing chain had a similar issue with a camaro. Same cylinder

[@marcus-gm3sc]

Have you disconnected the battery?

[@VetOnVettes]

I have. It spent 24 hours disconnected. 👍

[@Nontent-z4j]

Put the ECU in rice, located inside your passenger fender

[@VetOnVettes]

Yeah, I took it out two days ago. I didn't appear wet and the connections were clean. Still letting it air out in my office with a dehumidifier. Going to throw it back in tomorrow night 🤷🏼‍♂️

[@drewphillips3961]

Do a compression test on cylinder 6.

[@VetOnVettes]

That's the next thing on the list. 👍🤙

[@ah4800]

I assume you checked all the fuses?

[@VetOnVettes]

Fuses checked. I'll probably check again 🤷🏼‍♂️

[@ah4800]

@VetOnVettes maybe a compression test to see if there's a bent valve.

[@joeanthonyreyna5357]

How does it run at WOT vs part throttle ?

[@VetOnVettes]

It not perfect, but better at WOT.

[@joeanthonyreyna5357]

@@VetOnVettes 02 sensor fuses still good ? Maybe blew a 02 fuse with the water situation. I’ve had hell with 02s , ended up getting my tune changed to run in open loop so it ran off the MAF only

[@crodrc51able]

Injector?

[@VetOnVettes]

I'm going to do a deep dive into those tonight.

[@DB-be9wy]

You gave a c5 to your mom?

[@VetOnVettes]

? Not following

[@DB-be9wy]

@@VetOnVettes You said it was stressing ma out?

[@TheTrueAdonis1]

Just take it to a Mechanic.

[@gamerscubeixxi2152]

Number one rule when driving a corvette, get familiar with using your emergency flashers to prevent front end damage or water damage. But hind sight is 20/20. My advice. While not the best. Clear the codes. Sell it online and pick up a C6 😊

[@davidgalloway1526]

check and dry all your grounds and all electrical/computer connection...wd40 is your friend...