cylinder 1 and 4 misfire help!!

I have a 98 tacoma 4wd standard with a 2.7 the truck has 265k but has been well maintained. and have a rough idle and check engine light on. When I had the codes read they showed cylinder 1 and 4 misfire. I have replaced spark plugs wires coil packs, cleaned the MAF sensor. I don't notice any loss of power and the truck hasn't stalled out. I only noticed because of the slight shake when idling after warming up and then the check engine light coming on. What else could it be?

 

Clean the throttle body too and check your spark plug wires

 

Ive replaced the wires, how would I clean throttle body?

 

There is a ground on the coil pack bracket, make sure it's clean and making good contact.

 

Okay I will double check that, little things tend to get over looked haha

 

Right, might as well check all 3, theres one right behind the power steering pump bolted to the lower intake manifold and one on the exhaust side of the head all the way at the back towards the firewall, usually bolted on with the bracket for the engine harness.

 

And these are coil packs you are referring to?

 

The engine harness grounds.

 

Okay awesome didn’t know the grounds could cause misfire

 

Bad grounds can cause all kinds of stuff. Brother's truck had an intermittent no start recently caused by some corrosion on one of em. The ECU doesn't like having a weak ground.

 

do a compression check. She needs to be mechanically sound first. If the compression has differences greater than 10% between any cylinders she is going to need that fixed first.

 

Fuel injectors are a possibility too, though not likely both 1 and 4 go at the same time, but possible.

If that’s something you want to check you can swap the injectors from cylinders 2 and 3 with 1 and 4, just be sure to put new o rings on them, they’re cheap.

If the misfires move to cylinders 2 and 3, there’s your issue. In the future, instead of replacing all of your coil packs you can use this method instead of throwing parts/money at it.

If it’s not the issue no big deal, truck stays the same but you can rule those things out easily.

 

x2 on the compression test. Could be a failed head gasket or cracked headers. Easy enough to do, you can borrow the tools from autozone too. I'd also recommend pulling the plugs for a quick check, but I'm pretty paranoid after reading all the blown HG posts

 

That's my worst fear i have a compression test tool in the truck that's what i was going to do to start and see if there any work needs to be done on the top end. How would i check the compression and what are the ranges they should be st for each cylinder. I've replaced exchause manifold and got my exhaust flange welded had a couple cracks. The check engine light is the last thing i need to be fixed on it so I'm anxious

 

From my experience the RZ motors tend to lose head gaskets between the coolant passages and one cylinder, so maybe you'll be lucky, I don't remember what the compression is supposed to be, I'd expect like 160ish, but it'll be quickly apparent if you have an issue in a cylinder.

 

Do I turn the engine over to check the compression once the tool is plugged into spark plug socket ?

 

Yep, just unplug your coil pack harnesses and screw in the tester snug, crank 6-7 times per cylinder.

 

And if the compression is low in those two cylinders the heads need to be rebuilt ?

 

The compression test should be done with a warm engine and holding the throttle fully open (gas pedal floored).

 

Youd be losing compression somewhere, rings, valves, head gasket, anywhere is possible.