2001 Maxima GLE with 141K miles:

For a long time now, I have had a "popping" noise at the intake, but only when engine is bone cold in the morning. I live in moderate climate so morning temps are around 45-50 degrees right now, but this happens year round. Once the engine warms up, the popping out the intake goes away and the car drives with good power as normal, idles fine, etc, etc...

This past week, I changed the rear valve cover gasket due to oil leaks (had done the front valve cover about a year or so ago). I also changed the intake manifold upper gasket and the throttle body gaskets. I also changed spark plugs. I was **hoping** that maybe I was having an air leak at the intake causing the "popping" when cold, but I guess that is not it as the same problem continues.

From my reading on this forum I need to next look at:

1. Bad coil packs. How to troubleshoot? Those puppies are expensive from OEM. Any cheaper solutions. I know you get what you pay for, but sometimes, there are cheaper alternatives that others may have had success with.

2. Bad injector. How to troubleshoot?

3. Other?

I'm also still watching the oil leak on the rear valve cover. I saw a little smoke coming up yesterday after driving for the first time. I am hoping that is is just excess oil still burning off the exterior of the engine, otherwise, I think the "half moon seal" (?) may be next for replacement.

Thanks in advance.

 

Can you describe in different words this "popping" sound? A video link might help too.

 

"Backfire" out the intake is the best way to describe it. Technically, I know it can't be a "backfire". Perhaps an "infire". Anyway, definitely on the intake side. Perhaps a misfire?

Only happens when engine is bone cold from sitting overnight and goes away as soon as you drive 100 feet or so (engine gets warm enough). If you let the car sit and idle for a minute before driving away in the morning, it does not happen.

 

Very interesting. I have no idea. Sorry! Hopefully someone with more experience than me will chime in.

 

Thanks for looking. I'm hoping it is something like a bad coil. However, prefer to not just start replacing these things at random as it gets pricey.

 

For some reason I feel I've come across a similar issue to yours in another thread long ago. You might be able to dig and find something, but for the life of me I can't recall what the thread subject even was.

I'm sure someone will chime in soon. The site has just been pretty quiet lately.

 

I had replaced all four O2 sensors (all original and car at 143K miles) to get my car able to pass smog (O2 sensors wouldn't go "ready") and this problem went away. Just updating the thread in case anyone else comes across this issue. Kind of makes sense.

 

Well, sadly I spoke too soon. Still have the "popping" noise. Perhaps the best way to describe the behavior is "hesitation". This only happens when the car is bone cold overnight. I back down the driveway 50 feet in reverse. Switch to drive. Hit the gas and get the hesitation. By the time I reach the stop sign 200 feet down the street, it's gone.

 

So, this past weekend I replaced all of the ignition coils (Hitachi from RockAuto). The "popping noise" and hesitation has seemed to have gone away. So strange that it only occurred when the engine was bone cold. No idea why it is fixed now? An ignition coil with poor operation until it gets some warmth in it?

Anyway, new coils and away we go. Car is running great right now with recently installed new alternator, belts, idler pulley, IACV, O2 sensors, intake boot, and ignition coils. Fingers crossed it stays that way.