Flicker noise from engine when accelerating

Hi!
I have a 94 escort wagon lx, and have noticed recently, that when the accelerator is pressed, then there appears to be a noise, similar to those flickers you used to get on your bike as a kid, coming from the engine. i have got a check engine light on, with error codes 181 and 186, which sounds like a duff MAF and 02 sensor, so will be getting those changed out. Would the flicker noise be related to the sensor problem, or could it be something more serious?
wondering if maybe i should get a thorough tune-up once the sensors are changed.
thanks!

Does teh sound still occur if you rev it up in neutral?
Pop the hood and rev the engine by hand... see if you can isolate where it is coming from.
I am worried for you... I hope this sound is not a tapping from the piston...

Okay,
I just went and checked, and with the car in park and neutral, the noise does not occur. it is only when pulling away. I have noticed that the noise goes away when i take my foot off the gas peddle though. could this be an issue with timing??

thanks!

If it does not happen when parked then you are not dealing with an engine problem. It may be transmission or axle related (cv joints).

Okay, i have since had my o2 sensor changed, and changed the plugs in the car, and now, she idles well, however this flickering/woodpecker chattering sound is still happening. Also now, when i get up to around 70mph, then the car starts to sputter. could this have been the result of the spark plugs/o2 sensor being changed. it runs okay when below 65, but as it heads towards 70 it starts to sputter. it wont reach 70 mph as i am worried something might happen if i push it. i know i have tranny problems, and have an internal leak somewhere, which i need to get fixed, but would that cause the issues i have?

Okay, I have since discovered that either the rocker or lifter in the engine is whats causing the chattering/woodpecker sound. i can buy these parts and get them fixed, so that isnt a problem. i have also found out that the tranny leak is caused by a "rear seal" where the tranny and the engine connect. i have been told that it would be easier to junk the car than to try to get it fixed. how right is that. is that over kill. cant afford to junk it at the moment, and was wondering if it would be cheaper to get it fixed. any thoughts?

thanks

ps. also the sputtering has stopped. i think it was the lifters relearning after the 02 sensor was changed!