white smoke on start-up and engine knock

[onthecreek]

hi,

new to the forum, never had a problem with our 03 Murano SL until recently.

have had it in to the shop before and they weren't concerned but i am. the check engine light is on again and it seems to be making more noise than before. it might be better described as tapping.

symptoms:*on start-up there's a poof of white smoke, both exhausts.*sometimes the engine will stall seconds after starting, starts right back up but i give it gas.*BIG PROBLEM...engine knock after going to same speed for a few seconds. it seems to be getting worse. it doesn't happen when accelerating from a stop, speeding up will make it stop when it happens. the last oil change, there was no metal in the oil according to the shop. the check engine light is on again.

i plan to take it back to the shop but don't want to get a run around. i'm sure they want to get paid to fix stuff but does this sound familiar to anyone? i'd like to be more informed when i talk to them.

thanks!

[blastoff99]

Ok, I'm not a mechanic, but you should probably prepare yourself for some really bad news.

First, check the oil. Milky? Be sure to look on the underside of the filler cap.

Then check the coolant. Does it look like there's oil in it?

If the answer to either of these questions is Yes, you have a problem. Actually you have a problem anyway, and I think it's a big one. The symptoms you describe could add up to a blown head gasket.

Keep us posted, and meanwhile, don't drive the thing.

[onthecreek]

thx....but, no to both questions. oil checked out ok, coolant is clean too.

drove it today, the check engine light is still on but there was no tapping noise. never happens for the mechanic either.

i'm taking it in this week.

[BBISHOPPCM]

White smoke and knocking are symptoms of a failing head gasket. How many miles are on this engine? It is possible that a small amount of coolant can seep into the combustion chamber through a leaky head gasket, and as the engine warms up, the small gap can close completely. Have them do a pressure test on the cooling system when the engine is cold.

As for the knocking... that CAN be caused by a break in the head gasket between two cylinders, but it usually gets worse as you accelerate.

[Macsleuth]

Hmm, what kind of fuel are you using?Maybe a knock sensor is out, not retarding the timing on acceleration and you have knocking, puff of white smoke? What's the temp out?Have you checked the transmission fluid level? White smoke can also be transmission fluid.

[tubbedz]

hi,

new to the forum, never had a problem with our 03 Murano SL until recently.

have had it in to the shop before and they weren't concerned but i am. the check engine light is on again and it seems to be making more noise than before. it might be better described as tapping.

symptoms:*on start-up there's a poof of white smoke, both exhausts.*sometimes the engine will stall seconds after starting, starts right back up but i give it gas.*BIG PROBLEM...engine knock after going to same speed for a few seconds. it seems to be getting worse. it doesn't happen when accelerating from a stop, speeding up will make it stop when it happens. the last oil change, there was no metal in the oil according to the shop. the check engine light is on again.

i plan to take it back to the shop but don't want to get a run around. i'm sure they want to get paid to fix stuff but does this sound familiar to anyone? i'd like to be more informed when i talk to them.

thanks!

1. White smoke on start up is normal on cold mornings, IF you have no water in your oil and no oil in your radiator, this is normal. If you have white smoke constatly throughout the whole day and overheating.....your head gasket is shot.

2. Engine stalls after starting. You will need to perform an idle air relearn and/or throttle body relearn as your mechanic must remember that the Murano is a "drive by wire" vehicle. Anytime any work is performed on the throttle body, you need to perform this afterwards. Most mechanics forget to do this.

Before you perform the idle air and throttle relearn you will need to do an ECU reset to clear all the codes. This is the only way you can perform the idle air and throttle body relearn.

3. Change your MAF sensor. Do not clean it as this will do nothing. The MAF sensor on a Murano uses electrons instead of heated wires, and there is only one exposed resistor. Look at it yourself , you cannot clean it. Buy a new one. The MAF will not throw a "code" as it will work within the minimum requirements. The only time it will throw a code is if it is completely dead and you are stranded on a deserted road. Don't buy a MAF from the dealer as it is $500, go aftermarket OEM.