99 2.7 4x4, Rough Idle Poor MPG. Update

I've done some searching around the forum, but seems to be that I can't find an answer (or at least an answer I like haha).
As the title says 99 Tacoma 2.7 4x4 5 speed Manual. Right now I am getting 12-15 MPG. 15 only on longer trips on the interstate. Driving style is pretty mild. That's around town 25-45 mph and a little interstate at 70 mph. What used to be 275-300 miles a tank is now roughly 200-220. When its idling has settled in (about 750 rpm) when its warm it shakes/vibrates. Its not crazy shaking, but enough to make me think "what the hell" every time.

Every time I think I have found a solution to this continuing problem it comes back. The last time I took it in for an oil change it came back with a bad TPS sensor code and a code for a random misfire. I don't recall the code numbers off the top of my head. I just assumed they were related. That was in November. Replaced the TPS and cleaned the throttle body. Everything seemed better for a week or so and then back to where I am now. This winter I didn't drive it a whole lot as my other trucks heater works a lot better so fixing the issue has not been a priority.

I did a "tune up" of plugs and wires when I first got the truck last May and the more I think about it the problems started after the that. Not sure if its coincidence or not.

$10 NGK 2087 BKR5EYA V-Power Spark Plug, Pack of 4

https://www.amazon.com/gp/product/B00CC0FKZ6/ref=ppx_yo_dt_b_asin_title_o05_s00?ie=UTF8&psc=1

$46 NGK (4441) RC-TX67 Spark Plug Wire Set

https://www.amazon.com/gp/product/B000C5M1YG/ref=ppx_yo_dt_b_asin_title_o05_s00?ie=UTF8&psc=1
These are what I used there. I believe I bought these off a recommendation from a thread I read on here. I just checked the plugs and wires and they seem to be in good condition still.

Today since I am working from home now I decided to do some googling and came across a couple quick tests to see if the head gasket was bad. Checked oil which seemed fine and took off the radiator cap to check for any bubbling there, no bubbling. I know these aren't definitive, but why not check.

New air filter, MAF looks clean but maybe I will clean that while I am at home, I had just assumed leave it since it looked good. Thinking about picking up one of those leak detector kits to test the coolant as well.

I'm not a mechanic, but can turn a wrench and tend to to avoid mechanic fees (and I enjoy it). If it comes down to it I will take it in and have someone with more know how go through it. Any help on things to check out or other relatively simple troubleshooting to do? I am not set up to fully set up to really go through it as I just have a gravel/mud driveway and no garage to use for extended periods of time.

Thanks in advance for any direction with this! Hopefully I am not missing any details.

 

Have you checked for vacuum leaks? That is a simple thing that will make it idle craptacularly.

I don't know the part number of the right plugs off the top of my head, but if they plugs you put in aren't the ones that the manual calls for, that is likely a problem.

 

I will look into the vacuum testing! Thank you.

I just checked the manual and the plugs are correct.

 

Just went out quick on "break". Pulled plug wires off of the coil packs one at a time. That definitely changed up the engine. Question on the coil packs though. On the cyl 2/3 pack when I pulled those it was arcing to outside the pack, but on the 1/4 pack I didn't notice it arcing outside of the pack at all? Could have been I just did look at the right angle. Is that a normal thing to happen when you pull the plug wire? or should the arcing be contained mostly to the inside of the pack?

Disconnected the MAF at the end and it stalled the engine.

 

Your braver than me. Lol, if you ever get bit by that try not to put your hand in the fan

 

Or dumber...its a fine line I guess lol

 

Check your exhaust manifold gaskets thats what it was for mine

 

Found a friend with a compression tester and found my problem. Cylinders 2,3,4 all have normal compression, but cylinder 1 is at about 50 (dry and wet). So I guess the next thing is to take off the cover and start checking out the valves. Hoping one is just out of whack, but my gut is saying probably burnt up. No evidence of coolant in oil or vice versa and its not using any so I think I am safe on the head gasket side. Though if it comes to taking the whole head off I'll have replace that too