Hey all

No idea how else to describe it but it sounds like my truck has the hiccups. Some background info first. Last Monday I changed the spark plugs on my 2008 toyota 4runner. However like the idiot I am I forgot to plug the MAF back in and started the truck up and it ran awful. I plugged it back in started it up but it was still running rough. I was getting the valve cover gasket changed later on in the week so I limped the truck to my local shop.

The truck was ready Friday and all seemed to be fine. I payed my bill and was on my way. However I went to merge onto the highway on Sunday and the truck wasn't reving correctly. Again the best I can describe it is as a hiccup as in the engine rpm would begin the climb, pause, then climb again. It only seems to be happening under hard acceleration or high revs.

What could this be? Something that I noticed was that after I got the truck back from the shop was that the coolant was low (the tank was almost empty) so I topped it off. I checked it again on Monday and the tank was almost empty again. So there could be a coolant leak somewhere? Only other thing that I can think which would indicate a coolant leak is that, I did a seafoam treatment and as I was letting the truck idle there was white smoke coming out from the right side of the engine bay. So maybe the head gasket is blown out on the right side? Only thing is that temps have been stable and the truck isn't over heating. I topped the tank off on Thursday and the level hasn't gone down. Maybe there's some excess fule in the engine? No codes, no knocking. I'll attach a video of whats happening. Best way I could get it to happen again was by putting the truck into neutral and giving it some gas. Other than this the truck runs perfectly fine.
Thanks for your time!

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UPDATE 06/27/21: Hello again. Trucks been back from the shop for about a couple of days and the hiccups are still there. As for the coolant leak the hose clamps for the upper radiator hose went bad so they replaced them. Leak solved!

They took it on a test drive but couldn't find any issues that would lead to the hiccups. The check engine light came on today so I took it to an autozone to see what the codes were. The codes were for the MAF, and that the engine was running too lean. Bought a new MAF sensor to get myself home and put it in. The Truck was almost stalling while I was stopped so I'd rather be safe than sorry.

Forgot to mention that the The shop that I originally took it to replaced the MAF, serviced the trottle body, and did an idle relearn. I started to notice the hiccup after that. Went out, bought a new MAF and dropped it in to see if that would fix it, which it didn't hence the post. So I'm replacing the MAF that I dropped originally to try to fix the issue in the first place. The fun never ends! Have an appointment with a dealership on Tuesday so fingers crossed they find something and fix it. Codes are P0174, P0171, C1201

UPDATE FOR THE UPDATE: Turns out the gas cap was just lose! Tightened it and the codes went away. Still had the hiccups though. Went ahead and checked everyrhinf that you guys reccomended and I couldn't find anything wrong. Gonna keep my appointment at the dealership just in case before I go on my 600 mile drive