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Damage after water puddle

Hey everyone,

About 2 weeks ago, we had a big rain storm that created nice sized puddles. Having to drive through them to get home from work, my car stopped like 4 times on the way home. It has been a big headache ever since.


2004 Pontiac Grand Am 3.4 V6

CAI with the filter being in the wheel well.

I found water in my oil most likely do the the CAI sucking water in.

Things I’ve done:

New Spark Plugs

Motor Flush with Oil Change

New Fuel Filter + fuel injector cleaner

New O2 Sensor (One by catalytic converter)

Cleaned out CAI filter and tubing

Cleaned throttle body

After these changes my car rough idles and hesitates. Water coming out of tailpipe (Don’t think it’s condensation) along with white smoke that smells like gas. Also, tailpipe sounds like it chokes. Coolant level remains full with no overheating issues.

OBD codes:




New spark plugs have carbon deposit (probably due to the P0171). Haven’t driven the car since its been done for the fear of causing more damage. I would like your insight on the next steps I should take. I would greatly appreciate the help. Thanks

All of the things you’ve done are proper first steps.

Fortunately you did not hydrolock. At this point the things I’d look at first are the igntion pulses and the exhaust. You could be dealing with water having gotten into an ignition component and/or with water in some low area of your exhaust system (converter housing, low pipe, muffler even) restricting flow.

My money is on the ignition system. Specifically perhaps the ignition coil.

I’ve seen engines ingest water where the connecting rods get bent causing the rotating mass of the crankshaft, connecting rods, and pistons to be thrown out of balance. This causes the engine to run rough at idle but smooths out as the RPM’s are increased. If this what has happened, then the compression ratio in those cylinders with bent rods has decreased. This could be what’s causing the misfire code and incomplete combustion in those cylinders causing the vapor with the gas odor.

Also, when water gets into the intake it comes in contact with the Mass Air Flow sensor. This is a hot wire anemometer. And if cold water comes in contact with this hot wire in the MAF sensor it damages the MAF sensor.

At this point the first thing that should be done is a compression test. This will confirm the possibility of bent connecting rods.


I’d get the transmission fluid and coolant changed as well. If water got high enough to get in your cai tube, then it probably got some into the trans fluid too. Also, if you’ve never changed either fluid, now is a good time to do so.

How old are the spark plug wires?

I have had the car for 2 years and haven’t changed the spark plug wires. Not really sure when the previous owner did.

Ok, so I just got done installing a new EGR valve and now I’m just stuck with the P0171 code (Running Lean)

I uploaded a video on youtube:

Not as much water this time which surprised me. If you have anymore insight it would be very helpful to me.

Thanks for all your comments.

I would look for a vacuum leak it can cause this code P0171. Could be a hose or an intake leak. Look at everything that pulls a vacuum. After looking at your video I almost think its your Mass Air Flow Sensor. Try and unplug the connector to it and see if it idles out. Doing this will set an CEL. I tried this on my sons 98 Ford Ranger and it did. We replaced it and it fixed the problem. Not sure if you will have the same resullts

I noticed that too when I unplugged my MAF that it idled fine so I went out and replaced it last night. Took it for a spin and it ran beautifully with no codes. Decided to take it to work this morning and soon enough as it got closer to its normal temperature, it started doing that again. Check codes and it gave me a P0131 and P0171.
Back to the drawing boards =. Thanks for the help thus far.

I have had the car for 2 years and haven’t changed the spark plug wires. Not really sure when the previous owner did.

I would start there. Plugs would not be effected by high water unless the engine hydolocked and maybe not then, but the wires are moisture sensitive. Not knowing how old yours are (older ones are more sensitive) I would change them and consider it just maintenance.

The code P0131 is for low voltage from the front oxygen sensor on engine bank 1. Inspect the oxygen sensor for cracks and check the wiring to it.

Do you think if I replace the front o2 sensor that the lean will be fixed?