Cylinder 5 misfire

Hello all, long time reader first time poster here. I have been having an issue with my 05 tacoma with the 4.0. About 6 months ago I started getting a rough idle for about 30 sec on startup and hesitation at highway speeds. I got a cyl 5 misfire code. I replaced the plugs and a new coil pack and that did not help. I ran some sea foam thru it to no avail so I took out and cleaned the injectors by hand. After that the code went away and truck ran great for a few months. Now the hesitation and rough idle is back worse than before along with a flashing cel on startup. Did a compression test and everything checked out good. Any ideas what it could be? I ordered a new injector that should be here in a couple days, but is there anything else I should check as well? I was thinking it might be a headgasket since the truck uses some coolant (half the reservoir or so) between oil changes and does not leak out on the ground. There is no discoloration in the oil however and the compression was good, so ideas?

 

Did you go with Denso plugs? If so, next step would be checking fuel pressure. I would lean towards failing fuel pump/wrong plugs versus bad injector.

 

Cylinder leak down test is where i'd start

 

If it's only on a cold start a head gasket would be suspect, the best test to check for that is pull the coil and plug out on the suspect cylinde, put a pressure tester on the cooling system, let it sit with pressure on it for several hours, and look down in the cylinder for coolant.

 

This, all the way. If you don’t have access to a scope, you can hold a white paper towel above the spark plug tube and have someone crank it briefly. Pink on the towel is bad news.

 

Yeah denso plugs. Same ones that were in it.

Okay I will test that later today. The rough idle is only on cold start and the hesitation is all the time.

 

I had the same thought when I saw it was an 05’. Hopefully that isn’t it

 

Been 2 months but to update I pressure tested the cooling system as dm93 suggested and sure enough, cylinder 5 had coolant in it. I replaced the head gasket myself. Gasket masters has a good video on YouTube. Thanks for the replies everyone.

 

Good to hear.

That is a big job. Awesome that you did it yourself