Help with misfires where to start ???

I finally got my code reader today and ran it and got 3 codes

PO300 PO301 and PO303 misfires

Where should I begin diagnosing

Spark plugs were replaced probably 2 or 3 months ago
Coils were replaced probably almost a year ago

Any suggestions

 

Well, you need air, fuel, spark,compression, and timing. Timing isn't the problem. It never is on these engines.

You're getting air.

Spark and fuel are all that's left to diagnose.

Fuel is pretty easy. Pull spark plugs out of all four cylinders and then crank it over a few times. You pulled all four so it wouldn't ever start on you. Now, dip whatever you can find that is long enough to reach down the spark plug holes and check it for fuel. If no fuel in those cylinders, then your fuel injectors are probably bad. Either that, or the connection is to them is bad.

If fuel in all four, then that would mean spark. Swap the 1 and 3 plugs with the 2 and 4 ones. Now clear codes and run it like that. If the 1 and 3 codes come back, then its *probably* not the plugs. Its either the coil packs are bad or their connections are. Easy way to diagnose this is to swap 1 and 3 packs with the 2 and 4 packs. Clear codes and run it like this. If 1 and 3 codes pop again, then its something in the wiring and the packs are good. Now if the 2 and 4 codes pop instead, then its the packs that are bad. Now, back to the spark plug swapping, if 2 and 4 codes pop after swapping the spark plugs, then they would be the problem.

Now after checking the spark and finding that all is good, all that can leave you with is compression. Easy way to check compression is with a compression gauge. Cheap at Harbor Freight. Remove fuel fuse from under hood and then run engine till it won't crank. Then remove each pack and associated plug, screw in the adjuster, and turn the engine over a few times. Write down what the gauge says. Hopefully between 120 and 170ish. Do that to all four cylinders. The numbers should all be around that range. If they aren't, then whichever one has a really low number is probably your problem and obviously, you're mostly looking at 1 and 3 cylinders to see if they are low. Low number equates to either your rings being shot or your valves being bad or, in the worst case, your head gasket. Well, I guess worst case is their being an little hell-troll inside your engine chewing on your pistons and pissing battery acid. Doubt that is the problem as well. Valves can either be too loose (rare) or too tight (common with Toyota engines). That's about it for home diagnosing because if the valves are tight, it can either be that they need adjustment or they are bad and need replacing. Either one is probably more work and skill that you will want to offer up because its can be a bitch to mess with them and honestly, I prefer shops do this work because if they mess up, they fix it free. If I mess up, then I have to do it again and I hate redoing work like that.

 

Ok thanks will doing this Asap

 

How do I remove the air intake it's directly over plug 3 ???

 

Unclip the air filter housing and remove the clamp holding the other end of the tube to the throtte body. Remove the clips and hoses from wherever they are attached and it'll pull out

 

Yeah it's a 4 cylinder and I'll hopefully have a compression tester by next week. I'm going to try switching plugs and coils around and clearing codes to see if that narrows it down.

 

Oh my bad 213,000

 

I'm not sure Ive had the truck just over a year
And to my knowledge I don't think it has since I've owned it

 

Ok went to harbor freight and got a compression tester so I should have an answer by tomorrow

 

Do I need to remove all plugs and could when testing compress or just one at a time ??

Also here's a pic of the coils and plugs in order

Not the best quality but you can definitely tell #1 is black

 

Hopefully so , I should have the compression numbers on here tomorrow morning

 

yes you need to have all plugs out when doing the compression test or you wont get accurate numbers.

people who try to do it with only one plug removed don't know what they are doing and making decisions based on bad inaccurate readings

 

Keakar is correct, the proper method for compression testing is to take all plugs out.

 

Well I cleared the codes and replaced both 1 and 3 sparkugs ran it for a few minutes and nothing popped up but I'm still doing compression test today

 

Cylinder # 1 took a few revolutions got to 120

Cylinder # 2 150
Cylinder # 3 170
Cylinder # 4 170

What ya think guys ??

 

Well drove it and got 10 minutes down the road and misfire cylinder 1 pops back up

 

Just cylinder one? Did you check fuel in that cylinder or swap plugs or coil packs yet?

 

Used same coils , I'm going to switch #1 and #2 coils today.
They are pregapped ACDelco spargugs from autozone.

I didn't think its the coil because they've went out before and my truck would barely move. I could put it to the floor and RPM's would stay in the 2,000's.

But I will switch coils today. And clear codes

And if it is the injector do I need to replace or can I clean it ???

Also how do you remove it???

 

Some clean them but I've never had luck doing that. New injectors arent crazy expensive. You will need new o-rings though when reinstalling. After coils, plugs, and injectors it gets expensive so don't rule any of those out just yet.

 

How do you remove injectors ????