Engine Hesitation and Pop?!?!

[uglydave]

2002 2.5 TS automatic with 136,000 miles. Driving from Cape Cod to Portsmouth today, the car did great in traffic in Boston and great on the highway. I get off the highway in Portsmouth, come to a stop sign, accelerate and the engine hesitates wicked and fluctuates rpms badly. I lay off the throttle and then give her 3/4 throttle and the engine POPS! I backed off, gave her 3/4 throttle again and it pops again. The noise is a very distinctive "pop" from the engine. She continues to hesitate if I give her anything more than just a little throttle. So I pulled over and looked things over... one of the boots that covers the spark plugs had popped out a little bit. When I opened up the oil cap there was a decent amount of smoke that came out, and the oil has about a quart, quart and a half low. The engine was wicked hot, I mean everything in the whole bay seemed comically hot. On a side note, this is not the first time the car has been low on oil and been smoking when I opened the oil cap. But I have never seen a puddle from leakage or smelled burning oil or seen blue smoke from the exhaust. I let the car cool down and drove it the last hour and a half to Naples without going above 3000 rpms and barely giving it any throttle. Once I got in town I gave it 3/4 throttle again and it climbed rpms and shifted fine, no hesitation or pop. Any ideas about what the hesitation and pop could be from? I appreciate any input and help!

 

[injulen]

Spark plug boot came loose, caused misfire? Not sure. Check your spark plug torques.

 

[drvsdwz]

sounds similar to a vacuum leak too, but it seems like you diagnosed the problem

 

[injulen]

Yeah to elaborate on the vacuum leak, I ran into that for the first time recently. Went to move my scrap legacy across the yard and it just wouldn't stay running. It would start, idle up to 2000 RPM, running perfect, and then about five seconds later it would just die out. If I feathered the gas I could get it to spit and sputter and if I floored it it would rev but then as soon as I took the throttle away it would die. 

Turned out to just be the large vacuum hose on the intake pipe had fallen off while I was messing around in the engine bay. Popped it back on, runs perfectly again.

 

[uglydave]

I checked the hose from the intake pipe when I was looking things over in the first place and it was in place and tight. I am wondering if it is a fuel ignition issue possibly; the chamber filled up with fuel when it was hesitating then when I gave it 3/4 throttle it ignited all the fuel and caused it to "pop"?? I'm going to pull the plugs later today, check to see how clean/black they are, check the PCV valve, and MAF sensor. Also I noticed my exhaust pipe is very black and oily. Which I am unsure the cause of?

 

[i-wagon]

Burning oil, which would explain where it all went

 

[uglydave]

Alright, so I pulled, checked, and torqued all the plugs as injulen suggested. The plug with the boot that had popped off was loose, I was able to take it out without a rachet. Also all the plugs were dry but black. I replaced the PCV valve. Pulled and cleaned MAF sensors. The car drove fine all day, only drove 10 miles or so. I guess I will see if anything changes. I changed the oil and only got a little over 3 quarts out. I'm going to do a search for it now but am curious as to why she burns oil? Any ideas?!

 

[i-wagon]

Mine burnt more with a bad pcv valve. But never enough to go down more than a quart. Could be several things, including a nearly cooked motor.