Jetta Problem

I have a 2002 VW Jetta and everything about it is great except for this mysterious problem I have sometimes when it rains.

The car is always parked on the street as I live in the city, so when it rains overnight, or if the heavy snows melt, I get a pretty consistent problem. I think the issue is water in the gas lines.

Here is what usually happens. I have about a half a tank of gas and after heavy rainfall I start the car. The engine light comes on and flashes and car sputters and jerks for about 10 minutes of driving. While idling at stop lights the sputtering is terrible but if I put the car in park and gently rev the engine the sputtering and jerking improve. After about 10 minutes everything settles down. Sometimes, if it doesn’t settle down, I will put in some gas and this always solves the problem. Based on this I have deduced that what most likely happens in water gets into the gas lines and there is a bad mix until the water burns off (when the engine gets hot) or I add more gas to dilute this effect. My question is: How is the water getting in, and more importantly how concerned should I be about this?

When I have taken it to a mechanic in the past with this problem they charge me $70 for the diagnostic and tell me I had a bad batch of gas. If this is fixable, and important enough to fix, I don’t mind getting it done, but I don’t want to waste my time and money to have the mechanic tell me nothing useful and take my money.

Thanks for any help!

Bad gas, much like a cracked cylinder head, is seldom the case. This sounds like a problem in the secondary ignition (plugs, wires, coils, etc). How long since the plugs were last changed? The plugs are often the root cause of problems in this area.

Drop by a local AutoZone, Checkers, etc. and have them pull the codes for you. They will do this free and it only takes a few minutes. Post any results back here. Chances are you’ll get a random misfire code or number of cylinder specific misfires.

In the meantime, if you have any WD-40 around, try spraying the coils and wires down a bit with that and note if the problem goes away or subsides a bit. This is NOT a proper fix.

What I should have added is that water is more than likely the cause of this but it’s not water in the gas; it’s moisture in the air and the problem is exacerbated by possibly spark plugs that have been in too long.

The solution I would like to try is a spraying with silicone. The silicone is a water (moisture) proofer, and a dielectric (electrical insulator). Spray the silicone on the ignition coil on plugs, and the other parts of the ignition (spark generation) system on the engine. Let us know the results.

 That CEL (check engine light) is just a kid in class waving her hand trying to get you attention because she has the answer. You need to have the codes read. Some places will read them for FREE. Try Autozone or Advanced Auto Parts. Get the exact code (like P0123) not just their translation into English and post it back here. 

  In this case I suspect the problem is the ignition system not the fuel, but the CEL check should resolve that question. 

Regarding warning lights:

  1. if the coolant temp light comes on, shut off the engine ASAP

  2. if the oil warning light comes on, shut off the engine ASAP

  3. if a FLASHING MIL/CEL comes on, shut off the engine ASAP

    ASAP means driving to the berm of the highway right now and not waiting for the next exit.

But if the MIL/CEL is not flashing, then it’s not an urgent indicator.