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01 Frontier Check Engine Light only in Heavy Rain

I have a 2001 Nissan Frontier SE Crew Cab 4x4. Whenever I drive in heavy rain the truck feels as though its going to stall after about 10-15 minutes of driving.

Acceleration is very weak and stuttery, and the check engine light starts to flash! Not just illuminate and stay lit but actually flash! I always reach my destination but I have to drive in in the slow lane with my hazard lights going because acceleration is very weak!

If I leave the truck over night, all operations return to normal. Only 1 time did the check engine light stay on, so I took it to a mechanic and the diagnosis after hooking it up to their computer was “Cylinder 6 Misfire”. There was non of the other behavior that I mentioned available so I drove it home. While driving home, the check engine light went off and everything seemed fine, until the next heavy rain!

I was wondering how could I get the truck to misbehave without waiting until a heavy rain! I happen to take the truck to one of those high pressure hose water car washes.

Sure enough, when the high pressure nozzles went across the grill, the check engine light came on after the 2nd pass and the truck felt as though it was going to stall! Voila!

After the wash, I attempted to drive it to the mechanics shop, but while on the way, symptoms gradually improved and the check engine light went off! So something is getting wet and causing the issues! After everything dries out the truck is fine. Can you guys tell me what is getting wet and causing the strange behavior!??? Its obviously something in the front near or behind the radiator

A flashing Check Engine light means major misfire(s) are occurring.

This can cause serious damage to the engine/catalytic converters.

Since this occurs when it’s raining, I’d be looking at the secondary ignition components.



This is very easy for a mechanic to diagnose, just spray some water on the ignition wires. Or watch for arcing at night. Almost certainly the ignition wires.

You’ve already done a good job at the preliminary diagnosis. The problem is likely in the high voltage part of the ignition system, as that’s the part that is most susceptible to failure due to moisture. You could try just replacing the coil for cylinder number 6 if you wanted to make a guess. But the best approach is to take it to a shop where they’ll have ignition testing equipment. They’ll probably spray water around the engine compartment while they do their testing to narrow down which component is failing.

Years ago I had a VW Rabbit that would stall out every time I ran over a puddle. I’d then spray water over the engine compartment in my driveway, from every which direction, and of course it would never stall then. Eventually I just removed the coil and inspected it on the bench, and immediately say a small crack on the underside. Replaced coil, problem solved. I expect your experience will be similar; i.e. troublesome diagnosis, easy solution.

It seems all of the engines for the 2001 Frontier use a distributor

So I’m with @BillRussell on this one . . . just replace the wires.

May as well go for the full ignition tune-up, while you’re at it . . . plugs, wires, cap and rotor

I honestly see no reason to pay for a diagnosis, as this vehicle has the classic symptoms of bad secondary ignition components, most likely the wires have physically degraded

If you’re even moderately handy, you could do it all yourself. Consider it maintenance. The truck’s probably got more than a few miles on it, anyways. If it fixes the problem, you’ve killed 2 birds with 1 stone . . . done the maintenance AND fixed the problem

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A flashing check-engine light means to shut the car off and call a tow truck. If you keep driving it when it’s flashing, be prepared for additional damage that could have been avoided.

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When if ever were the spark plugs replaced? Aged, high miles plugs with widened gaps can cause arcing from the plug wires; especially when the moisture is high.

I’d say plugs and wires and go from there.

Thanks for the replies to everyone. Today I finally swapped out the plugs, wires, distrib cap and that little thing inside of the dist cap. Started up and sounded like a marble or two was rattling around in the engine! Turned if off then rechecked everything (nothing found). Stared it back up and the mables sound was a little less. It ran a little rough for about 30 seconds then finally smoothed out (is this normal?).

Now I just need to wait for a heavy rain or go to the high pressure car wash to see if swapping everything fixed it.

On a side note 5 out of 6 spark plugs looked as though they had some arcs! lots of discoloration where the white part meets the bolt…

Just theorizing, but the rattle could be caused by some tiny bits of debris such as a piece of carbon, plug tip, or porcelain from the spark plugs. When running, the debris will turn red hot and cause detonation.
Soon it will vaporize and/or get spit out past the exhaust valve.

I’ve seen this a few times in the past. Assuming that is the cause it’s nothing to worry about since it faded away quickly. That may not be it. Just sayin’… :smile: