05 Pathfinder LE - Runs Rough on Cold Start

[BCPathfinder]

I have a 2005 Pathfinder LE (Canadian V6 4WD) that I've owned since new. Last winter, I started noticing that on a cold start, the engine would seems to struggle. I would describe it as running rough (incomplete combustion?) but after a few minutes of driving, the problem would clear up and the truck would run as normal. No Service Engine Light or any other warning lights illuminate.

I had the dealer look at it - they couldn't recreate because our climate on the west coast isn't cold enough after it was driven for twenty minutes, and I was unwilling to leave the vehicle there overnight in the hopes it showed up for them (it is very dependant on outside air temperature). In any case, the problem is back this winter. It seems incrementally worse (takes a minute or two longer to resolve), but otherwise the same: engine starts, runs rough for a few minutes, engine heats up, problem goes away.

Vehicle is fully dealer serviced since purchased; up to date on all the usual service schedules. Would welcome any suggestions that anyone might have? The truck is in excellent shape given its age and sees fairly light use right now (it can go a few days without being driven and trips are a mix of short trips and 35 km highway drives).

Thanks for any suggestions!

[ShipFixer]

Spark plugs? Try some fuel system cleaner?

[Spatula]

"Cold" is relative, and temperatures in B.C. today range from -27°C (-17°F) to +8°C (46°F) within the province. At what temperature do you start to have issues? Does it have a block heater?

[BCPathfinder]

"Cold" is relative, and temperatures in B.C. today range from -27°C (-17°F) to +8°C (46°F) within the province. At what temperature do you start to have issues? Does it have a block heater?

Fair enough! I'm more on the warmer side of your range. Seems to happen around 4-8 degrees or so, but not consistently.

[BCPathfinder]

Spark plugs? Try some fuel system cleaner?

Sparkplugs haven't been done in a while; how would I know if they needed changing?

Does fuel system cleaner actually work? I had always heard those sorts of additives and cleaners weren't good for the car.

[Chris Steffen]

Take them out, check how clean they are, inspect the insulation for cracks, check the gap. But if regularly serviced then they should be fine unless when last replaced one was a dud.

Could also be one or two of the coils. Each sparkplug has a coil. One of them could be faulty. My BMW or XTrail was running rough when cold (only 15 degrees C cold that is ) but when warm was ok. My mechanics diagnostics found that one of the coils had deteriorated over the years. These things once warmed up can work fine but when cold give a problem.

Could also be a vacuum hose leak on the intake side. Perhaps a crack or ill fitting hose that sucks in air when cold but when hot the hose expands and closes the crack?

Dealer should be able to check all of this.

[ShipFixer]

Spark plugs? Try some fuel system cleaner?

Sparkplugs haven't been done in a while; how would I know if they needed changing?

Does fuel system cleaner actually work? I had always heard those sorts of additives and cleaners weren't good for the car.

NGK says they're good for 100K miles, but I just replaced mine at 80-90K. One electrode was a little eroded (I threw a P0430 code and checked them). As they age, running rougher when cold is expected.

Yeah, fuel system cleaners work. Seafoam is really good.

[Chris Steffen]

Any feedback on what the problem was?

[BCPathfinder]

No, problem went away, until today when I started, drove for a couple of minutes, got a blinking service engine soon light for about twenty seconds, which quickly resolved, and then pulled over. Drove back home (a few hundred metres with no SES light illuminated, then parked. Will call the dealer in the morning to see if I can drive it in or should have it towed. What I read about catalytic converters and this sort of behaviour is petty scary, so will take the service department’s advice.

[ShipFixer]

No, problem went away, until today when I started, drove for a couple of minutes, got a blinking service engine soon light for about twenty seconds, which quickly resolved, and then pulled over. Drove back home (a few hundred metres with no SES light illuminated, then parked. Will call the dealer in the morning to see if I can drive it in or should have it towed. What I read about catalytic converters and this sort of behaviour is petty scary, so will take the service department’s advice.

Doesn't hurt to start with the plugs...that would be step one anyway. If you can resolve an aging or worn plug issue early enough you can save your catalytic converters. Do you have a code scanner?

[BCPathfinder]

Called the dealer, they thought it was safe to drive, so we drove it in this morning. I got it back from the dealer today, there was no stored code, oddly enough. I wonder if the fact it was flashing and didn't go solid meant a code wouldn't register. Then did find a leak in the plenum (I had no idea I had one of those), but they couldn't attribute the engine trouble to anything specific, and didn't want to start replacing things without knowing more. It was due for a fuel injection service, so we did that thinking that might be a contributing factor, and changed the oil (due) at the same time. Will see what happens, but it is running fine for now. The plenum sounds like a fairly big job, and they say the leak isn't good, but it's not horrible either, so I'm going to wait and see if things deteriorate further before doing it.