P0303 Code

I have an 03 Tacoma with 277k miles on it. Recently been having rough start ups that led to an all out 3 cylinder run on the way home.

I ran the codes and i got the P0303 code (along with some EVAP codes 0442 or 0456)

I swapped cylinder 3 and 1 coil and plug and the code followed to P0301. I threw a new spark plug in and it ran fine. Problem solved right ? no

Problem came back after a tank of gas. Says cylinder 3 again

Checked compression. 145-150 in each cylinder.


Need some help here. Truck will start up rough and then smooth out with any throttle. Also will run rough when under a heavy load (pulling jon boat).

I thought for sure i had a bad cylinder but after compression check i don't feel that way. Maybe injector ???

 

So you swapped the coil and plug, then only replaced the plug? I'd be looking at that coil...

 

sorry, i replaced both coil and plug

 

What about plug wire?

 

What engine does your truck have?

 

All my coil packs went out within 500 miles or so of each other. You may have a similar situation. I have to wonder if those are the original pacs considering your mileage. Mine lasted 150k.

 

It's a 3rz.

No plug wires. It's a coil over plug.

Cylinder 3 has new NGK plug and Denso coil.

Not sure if the old coils were originals or not but they were definitely Toyota parts.

 

Do you have any other codes? Fuel trims look ok?
Any vacuum leaks?

 

If your new coil is now on #1, I would swap #3 out with number #1 again and see if the code moves to #1. Just me, but if the others are original coils, your running on borrowed time, and I'd replace the rest. I had a few of mine go at very inopportune times and places before I wised up and changed the rest. Of course, only use Denso. Rock Auto has them for a decent price when you use the TW discount.

 

It has had the P0442 code since I bought it about 100k miles ago. This last go round is when it popped the other evap code, I think 0456.

Vacuums all look good.

Cylinder 3 is the one with new Denso coil and NGK Iridium.

I agree I'm just on borrowed time with my coils in 1 2 and 4. They are definitely on their last leg.

Just got me baffled as to why 3 is still showing misfire after new plug/coil.

 

Yea that really is bizarre man... Does the truck call for iridium plugs or copper? I know the 3.4L is very finicky when it comes to spark plugs if you don't put in the dual electrode copper. Not sure what plugs the 2.7 comes with from the factory, but it would be a good idea to change all 4 out with factory plugs from the dealer.

 

It's very weird. I think factory they all come with copper. These are the same part number as factory just with an IK or something on the end. Had ran them for about 30k before all this sorted out. But yes I agree these Tacoma motors are very picky a out spark plugs. I'll pick some coppers up and see if that works.

 

I just ordered 4 Denso Coppers and the rest of the coil packs. Going straight back to what the manual says to use.

Hopefully show up by the weekend so I can test it out.

 

I did the same plugs when I did the last two pacs. Your issue is not exactly the same as mine was though. Keep us updated.

I've also had a slew of emissions codes. Had to do air/fuel & o2 sensors, charcoal canister and the VSV for evap under the hood. I don't remember all the various codes, but it took some work to flush them all out.

 

Finally got back into town yesterday and replaced all coil packs and spark plugs. I pulled the EFI fuse to reset the CEO.

Started it up and ran great.

I went ahead and put some injector cleaner in the tank and filled it up with premium fuel. Drove for about 45 miles and everything was great.

This morning when I started it up, it was doing the miss and low idle again on start up, then smoothing out when throttle was applied.

Back to the drawing board.

 

Your symptoms are similar to mine, I had a cyl1 misfire. Just had valve cover gaskets replaced, and the kit came with spark plugs, wires, and I purchased Denso injectors separately, That did the trick for me. Still have a weird issue of pinging at high speeds but I think its either valves out of adjustment, or bunch of carbon build up. idk.

But yeah.... Injectors wires and plugs.

 

What do you mean "reset the CEO"?

 

Phone autocorrect got me. Reset the CEL not CEO

 

Ill see if it will throw a code this time or not. Usually it just shows a pending code of P0303.

I'll let this tank of gas burn through and see if it gets any better with the injector cleaner. If not I guess I'll be swapping injectors. Just hate throwing money at parts I'm not sure will fix it.

 

Its odd to me that it ran good after you put in the new plugs and coils, then reverted back to running bad. Have you looked at the new plugs since it started running bad? Try pulling that fuse again to see if that changes anything...