did a 2 hour trip today, truck ran great. started it up an hour ago and it was misfiring bad. eventually the engine light came on and it gave a p0304 code. misfire #4. so i started poking around the wires and decided to pull some plugs. they are wore out. i guess its been several years since i've changed them. time flies......

anyway the point of this thread is to ask about plugs. there is a sticker on my engine saying to use dual electro spark plugs.

haynes manual says to run ngk bkr5e, which is single electrode, and that is whats in my truck now. wtf?

whats up with the sticker?

 

Stock was three NGK BKR5EKB-11 (3967) on one side and three Denso K16TR11 (3194) on the other--both are dual electrode. Because the 5VZ-FE waste spark ignition fires twice in every cycle, once for each cylinder on the circuit, spark plugs wear twice as quickly. Therefore, Toyota felt that single electrode plugs would wear too quickly. This may be why your single-electrode plugs show so much wear.

Haynes is toilet paper, and not much good for that. See FSM page below.

 

cool man, thanks for the info. those spark plugs have been in there 5 years and probably 60,000 miles now. i'm sure any would be worn out.

so i replaced the plugs. at first i just changed #4 and it ran great, for a second........bad idle/ misfire came back. swapped out all the plugs, cleared code, then took it for a drive. p0304 popped back up again.

my next step is to test the plug wires. i changed those about 5 years ago when i did the plugs. when i pulled the boots out, some of the interior rubber stuck on to the plug. i blew it off and reused them anyway. maybe i should just replace them.

any other ideas? swap the coil with another to see if code continues. thats all i have for troubleshooting......i do need a timing belt change, i'm about 30,000 miles past due.

 

oh and regarding haynes, i know its crap but it gives the basics. i even checked a few forums and websites and they quoted the same single electrode spark plugs

 

Yeah, now that you have good plugs, coil swap is next. Or just hold the #4 cable close to good engine ground and see if it sparks. (FSM recommends this procedure, it's not as flaky as it sounds.)

If you rule out spark, next suspect is injector--stethoscope, electrical test are indicated. If no joy there, time for compression test.

 

˟˟˟˟.....yeah i knew this was going to get complicated. didnt work on the truck today, was raining on and off. will probably do some stuff to it this weekend and get it figured out.

injectors are under the upper intake huh? i cant recall ever seeing them.

 

Burned valve is a most likely culprit for low rpm misfire, accompanied by low compression 171 psi is std, low rpm misfire starts at around 110 psi cold compression, also causes plugs to have deposits or odd appearance, only fix is head job and the sore feeling that you should have been doing the valve clearance checks the the factory owners manual says "are required every 60k miles and cannot be skipped"

if your luckie and the compression is still at 171 psi

its hard to get the dual electrode plugs now, but if you get the irridium or platinuim 4 way plugs they work well and last a very long time 100k miles or so

 

i checked rockauto. both recommended plugs (dual electrode) can be found there.

i doubt its a burnt valve. only 140,000 miles on it and i've had this truck since 65,000 miles. i've taken care of it. color/deposits on the plugs all matched and looked perfect. its probably a bad coil or injector. every other oil change i throw seafoam in the fuel tank, so if its an injector, its probably a malfunction and not clogged. i have never heard any ticks or weird noises coming from this truck. only issue i've ever had with it was a bad O2 sensor.

i should just buy new intake gaskets, valve cover gaskets, water pump, and a timing belt set and rip this engine apart. also check valve clearances while in there.

 

just moved the coils. still throwing p0304 code. started checking the spark plug wires.....#2 wire shows 1.6k ohms and #4 is showing 19.5k ohms. think i found the culprit.

 

My NAPA has the recommended NGK dual electrodes in stock, and has for the last 15 years.

FSM states, "Maximum resistance: 25 kΩ per cord". But being that far away from the others, I would say it is time for a new set. Get OEM Sumitomos, the NGK TE-66 at NAPA, Amazon or elsewhere--I have 80k on mine, or Densos.

Are your existing wires factory Sumitomos? They have the year on the wire insulation.

 

no they are some aftermarket brand that i put on there when i bought the truck. probably bosch. but those too are about 5 years old and have 60,000 or so miles on them. i have a set of 7mm NGK's coming tomorrow morning. 31.99$ at oreilly's. part #4412 which is also the TE66's you are talking about.

 

and ya, i checked the #6 spark plug wire and it showed 1.9k ohms. it is longer than the #2 so it should have more resistance. so the #4 wire is definitely way off compared to the others.

 

installed the new plug wires today. running just fine now. thanks for the help guys