What's my next move?

My 2001 2.7 has been throwing p0300 & p0303 (misfire) codes for the last couple weeks. Here's what I've done so far.

Replaced fuel filter.
Checked plugs - ok
Swapped coil packs - no change
compression test - #3 about 5% off but within limits
Leak down - slight leak in #3, no bubbles in rad, no noise in oil or exhaust!
Seafoamed in break vac line - lots of white smokeand ran a bit smoother.
Bottle of Seafoam in current tank of gas.

What's next? I'm thinking injector swap, but I guess I need to find o rings.

Maybe sticky valve? Idk there. Bad Cat?

any help appreciate!

UPDATE:
I have now cleaned the throttle body real well.
Added some seafoam to the crankcase.
Replaced the fuel injectors
Replaced spark plugs (denso oem, .043 gap)

All the above with no real noticeable improvement, though a bit more throttle response. A p0303 code will still come on, sometimes at a cold startup. A flashing CEL will happen under load conditions such as climbing a grade.

 

What codes are those?

 

300 = random misfire
303 = misfire cylinder #3

 

Just an update.

I've cleaned the MAF sensors and checked by washable filter. All there looks OK and made little to no difference. I'm still throwing a p0303 daily. I did take it on the freeway last night and really stomped on it! No codes and it felt like it was more responsive, still working through the tank with the Seafoam. If this tank goes and still is throwing the 303, I'll look to pull the #3 injector. I have 160k on this truck and to my knowledge nothing has been done with the injectors. Do the injectors need an annual maintenance or something?

 

check the plug wires

 

You said you checked plugs, however one may still be bad and it looks good, trying replacing the plugs

 

mine did this and it was because my spark plug boot would come off it was cracked and you couldnt see it. i bought all new spark plugs and wires and since then never have had a misfire since. it would also run funny, thats how i knew something was wrong. the rpm range was way off due to one cylinder not firing right.

 

Thanks for all the suggestions, I have some plugs on order.

Today I added 1/3 Seafoam to the crankcase in hopes that something is gunked up in there. I did the paper at the tailpipe trick, and it didn't suck in so I thought that was good.

Also I cleaned up the throttle body. I looked in there first and it didn't look too bad. But I sprayed some cleaner in there and WOW! I cleaned and cleaned, as best I could without taking it off (as I don't have a gasket). Well this made a marked improvement. The RPMs are much more steady and the idle much more smooth. So far no codes.

I will report back more after I change the plugs.

Thanks!

 

I had an ignition problem a while back on my 2.7 ltr 2000 Tacoma. The main issue was a bad plug wire.

 

If you put denso platinum plugs in it then that made mine misfire. I put the regular ngk's in it and presto all fixed. I got 196,xxx on mine. That engine doesn't like high dollar plugs. When I pulled the platinum plugs they looked fine too.

Murph

 

(I've updated the first post to reflect my "progress" if you will.)

Yesterday I did the following:

Replaced the fuel injectors
Replaced spark plugs (denso oem, .043 gap)

All the above with no real noticeable improvement, though a bit more throttle response. A p0303 code will still come on, has been coming on at a cold startup. A flashing CEL will happen under load conditions such as climbing a grade. Engine still runs rough especially at idle. I can post vids if that would be of interest... The plugs and injectors looked ok, but the #3 plug was a lot more brown (plug read guides show "normal") then the others. This after the seafoam in the last 400 miles.

Also I pulled the plug on the #3 injector when running and it stumbles, so I know I'm getting fuel there. Also pulled the #3 spark wire and again stumbled and turned off, so apparently it's firing.

Also sprayed some carb cleaner to look for a vac leak, but found nothing.

I'm thinking of trying to clean the o2 sensors. Maybe their getting a bad reading to the ECU?