Expert: Roland Finston - 11/4/2009

Question
hi, i have a 2001 infinity qx4 that has 130,000 miles on it.  when i step on the gas/accelerate it is making a crackling noise and it getting louder and more pronounced...what is going on????
along with this sound (which i hear towards the front of my suv) is another sound towards the back.  the sound towards the back has happened three times.  all three times, i swore that there was something dragging under the back of my car or flat tire sound. after pulling over and checking under and all tires it would stop?????? help please;o)

Answer
Hi Kelli,
If the crackling sound is also more pronounced when you are turning to the left or the right, and if the SUV has front wheel drive, then my thought is that you have a constant velocity joint (cv-joint) which has leaked out its grease and run dry of lubrication which is quite common. I usually describe the sound as 'clicking' but in any case just look underneath at the drive shaft on each side, and notice that there is corrogated rubber boot around it just behind the wheel housing. If that boot cracks then the grease comes out. You can either replace the boot or put in a rebuilt drive shaft. There is also a cv joint at the inner end of each of the two shafts but those usually last much longer and are harder to see unless you climb under or lift the vehicle.
Another possibility is 'pinging' which is a sound that comes from the combustion chambers of the cylinders and that now days is due to using too low an octane rating in the fuel tank. It also could be due to electrical 'arcing' occuring along the spark plug wires. That would be visible if you just open the hood on a humid night and observe for arcing, even while it is idling. That would require that you replace the spark plug wires to correct it.
On the rear noise, it is very hard to say. You may have to wait until it happens again and see if you can determine any concurrent factors that come into play at the time so you can reproduce for a mechanic when you need to illustrate the problem.
Roland