greetings - truly sorry for the long post.

What is the engine part circled in the picture, please, and would it cause a rough idle and poor/struggling acceleration if bad?

This is a 1999 Volvo V70 Base Model

Most recent codes:
P0300, P0113, P0102 (I replaced the MAF and 113 &102 codes cleared)

History: Have had issues with check engine light and hesitation and stalling for the past two years. Mechanic can never find the problem. At first he replaced several vacuum hoses and this fixed issues for about three months. Then he replaced some O2 sensors and again this seemed to do good for about a month. Though about the PCV system, but it passes the "glove test". The symptoms are just as stated in another post that outlines MAF and ETM failure. The car is right at 111,000, so the mileage fits with these parts needing to be replaced. I also noticed the car started "using" oil about 1.5 years ago, though I never saw any external signs like puddling or oil in the engine compartment. Mechanic said the car was built to use oil and that he would check it again in a few thousand miles. Blah.

Having recent issues with engine running very rough. Did some repairs myself. I replaced the ETM with one from Xemodex with my software preloaded. Car ran better, no more stalls, but you could still detect a hesitation every 10 seconds. Xemodex suggested changing the Engine Management Relay. I did so with a NAPA part, as they were accessible, but no improvement. Check engine light came on solid a few days later. Mechanic said the first thing he would do would be to replace the MAF because the one on there was an aftermarket. The car started running more and more rough as the days went by, so I replaced the MAF. Check Engine light cleared, but no performance improvement. A few days later it started showing a misfire with a blinking check engine light with the check engine light eventually going solid again. At this point the car was running so rough that the old lady bingo fat on my arms would shake when the car was at idle. Not pretty. I replaced all the spark plugs, hoping to clear the p0300 code. Replaced the oil cap, because there was oil under the spark plug "dust cover". This, I'm sure, is where all the oil was going. The rough idle was greatly diminished, but the every ten second hesitation and poor acceleration was still present. Decided to drive it for a bit and the check engine started blinking within 5 minutes of driving. I dropped it off at my mechanic's shop rather than getting stranded.

So, all of that to say - what's this part and anyone have any ideas about what might be up with this car?? Thanks.

 

perhaps it is the idle control valve? see reply #17 on this post (sorry for link to other forum):

engine shudder and rpm drop while coming to stop (184K miles now-FWD 2000 V70XC))

 

This is the Idle Control Valve (ICV). Chatted with my mechanic. Nice to not be clueless. Twas strangely difficult to find this on the internet and in forums. Plenty of references to the ICV, but no pictures or tech videos that looked like mine. Perhaps because I have a 1999. Perhaps because I have a non-turbo. Perhaps it's just because I have a Volvo. haha.

Attached is a close-up picture a parts site just in case anyone else out there is looking for the same info someday.

Oh, and the final piece to the rough running of the car was one simple failed spark plug coil.

PCV system has never been changed, and mechanic says the pooled oil under the spark plug dust cover is probably from a PCV that needs serviced. He thinks I can do it myself and save a few hundred $. haha again, but I will probably try.

Cheers.

 

That probably is the IACV. I was going to correct you, but it's different on my '98 turbo. Glad you figured it out!

As for the PCV, you can do the "glove test" to confirm, but the oil under the spark plug cover is a pretty clear sign that the PCV is clogged up. It's not that bad to replace, especially on a '99. Only about $130 in parts from FCP Euro.
If you aren't familiar with it, the glove test involves placing a glove over the opened oil filler cap while the car is running. If it sucks in, the PCV is good. If it blows up like a balloon, it's definitely clogged. There are lots of DIY resources if you want to do the job yourself.