Unsure about repair

Hey fellow taco truckers, an issue has developed with my 07 Tacoma that I've been advised could be a couple of different things, but I'm not certain how valid they are. The issue is when on the highway if I start to climb a hill the truck will begin to do what I can only describe as a shudder giving me a feeling like it's having an issue changing gears. The second time it did this the check engine light came on and a guy at a local shop plugged a handheld diagnostic into the truck and came away saying it's either an issue with an ignition coil and plugs or could be a head gasket. He also used a testing device on the radiator which is supposed to detect combustion gases, but the blue liquid in it didn't turn yellow-green like it should if gases are detected like it has an issue with a head gasket. The coolant is low because it hasn't had the cooling maintenance it should've, but there's no sign of coolant leaks around or under the engine compartment. Initially I had the feeling of it being something with the transmission, but a couple people here are thinking coil or head gasket.

Has anyone experienced a similar issue and the solution was a coil or head gasket? If so I'm happy to head down that track, but just seems like there's potential it could be something else given the specific symptom. Certainly hoping for the coil if that could be the issue as it means a $400 repair vs. $4000. There's probably details I've left out that may help so if so fire away and I'm happy to provide any specifics that can help get a solid direction on things. This is a Double Cab Prerunner TRD with the 4.0 V6.

 

Hopefully someone else will chime in with a more detailed and thorough response but the first thing I would do given its age is a spark plug change, clean mass air flow sensor, replace PCV valve, change engine air filter along with oil. This is assuming it’s a relatively new vehicle (for you) and you haven’t already done these things. All of this is DIY stuff, cheap and easy to do, lots of detailed how to’s here on the forum. Start with the basics first (especially if they haven’t been done by you or if you’re doubtful they’ve been done recently by the previous owner) and work your way from there, best of luck and hopefully someone else steps in to take a swing.

 

Have an ‘01 that did the same, felt like a transmission stutter or slip. Ended up plugs and coil pack fixed it- was a misfire.

 

I’d like to know where to coolant was low?
And what the engine codes(s) were?

Was the coolant low in the reservoir or the radiator?

 

All great stuff that honestly I do need to knock out on the truck regardless of it benefiting the issue or not so thank you for the suggestions!

 

Thank you, that's exactly the description I would give the issue so I'm happy to know replacing the coils and plugs will hopefully knock this out!

 

Coolant is low in the reservoir and the specific codes were never shown to me at the shop that checked the truck. Going to have O'Reilly scan it too and I'll get the codes, but at this point happy it sounds like this is most likely solved with replacing coils and plugs.

 

My coolant was low in the reservoir after 8-9 years. But it never got low in the radiator. It’s normal for coolant the evaporator about of the reservoir over a long time. And you said the system has never been maintained.

I think I get the truck back, drive it, and check the coolant every week for a week or 2. If it runs fine. Drive it and don’t worry about the rest.

 

i'd recommend first moving the coil and plug from the misfiring cylinder to another and see if the code/misfire follows. Obviously have the codes pulled before doing this so you have a starting point. This will help you narrow down the problem though