P0300 p0303 p0306 misfire codes under load no mis felt or power loss

this one has me stumped as well as the mechanics who put the new engine in...
2002 3.4 auto 4x4 had new engine dropped in with new injectors, coils, wires, knock sensors, new maf, new vacuum lines snorkel etc... Engine runs rough at idle and has vibrations, runs fine on freeway and flat roads but as soon as I'm climbing a grade usually within about a minute at 2800 to 3500 rpm it throws a flashing cel and reads 0300 usually with 0303 0306 cylinders.. the weird thing is I can't feel it miss and it continues to power up the grade with no noticeable power loss or stumbles, sometimes the light turns off after I stop and sometimes it stays on after its done blinking ... coils have been moved around problem stays on those cylinders, leak down was acceptable although not awesome at 10% on a new rebuild.. new pcm and igniter have been swapped in to rule them out, they were not the problem,, anyone got a suggestion where you go next?

 

check the basics first... is the motor mechanically sound, do a compression test then move on to ignition. verify that the firing order is correct. If you can find a good diagnostics shop it is well worth the few hundred dollars to have someone with a PICO scope that knows how to use it diagnose this issue for you.

the flashing CEL is telling you that you are doing potental damage to the engine/cat(s).

 

Spark line for coil pack cylinder 3 and 6 is the first image and the second image is what the other two coil packs are doing, anyone care to suggest what is going on with the kv on 3 and 6 again it only throws codes climbing grades and I can't feel the miss, rough idle with some vibration is also pronounced when I run my 03 taco with 200k on it right next to it its quite a difference.. thanks chris

 

high resistance in the secondary is telling you the plug is having difficulty in firing and with all of the things you replaced it is indeed confusing. I have always "old schooled" these difficult to diagnose problems meaning a compression test and a vacuum gage to verify how mechanically sealed the motor is. Another old school trick is to put a paper towel up to the exhaust pipe and see if it sucks it back towards the pipe, if it does, there is a misfire, sometimes you can feel it, sometimes you cant. A steady needle on a vacuum gage generally tells you that there are no mechanical sealing issues... a wiped cam lobe will show up as a needle variation due to the lack of cylinder filling. as you can tell, there are too many possibilites to point to one and say, this is it. You are just going to have to start with the basics and move outward from that until you find it and it can be more than one thing.

 

I just fixed a misfire, turned out to be a failed Denso plug with less than 500 miles on it. Try moving the spark plugs and see if the problem follows it.

 

With your P0300 CELs I would suspect faulty injectors. Is your "new" engine a brand new engine from Toyota? If not, does your "new" engine have new Toyota injectors? Your initial post does not have much info to go on, and I would highly suspect there is anything "new" about the engine, other than it's being new to your vehicle.

From what you have written, I would think about the injectors. If you disconnect the injector plugs from the three injectors on the passenger side you can use a multimeter to test them. Their resistance should be between 13 and 17 ohms. It's more of a problem to test the resistance of the three injectors in the driver's side because you'll have to remove the plenum that's installed over them. But it's certainly worth the effort.

Injectors are not too difficult to replace, and a set of decent rebuilt injectors goes for around $180 to $200 from Motorwest postpaid.

 

Not much info to go on?? Did you read the post? Injectors were replaced and they check out and fuel trims are within spec ... the motor was built by Yota 1 I've never heard of anyone forking over for a new motor from Toyota, might as well throw an ls1 in there if your gonna dump that kind of money...
The problem here is intermittent thats why its hard to diagnose, we are either in the electrical realm here or possibly a cylinder issue, wiped lobe etc
I was hoping someone on here had been here before possibly or has seen a sparkling like that and was able to find the bug...

 

I just had a realization and I feel pretty dumb about not noticing it earlier... 3 & 6 fire off the same coil. I am not saying the coil itself is bad or the igniter is bad but maybe the wiring between the igniter and the 3-6 coil or the +12v power wire to the 3-6 coil. I looked through a couple of different wiring manuals and while all of the 3.4 ignition schematics were similar they are not the same. One thing that they did have in common was there are 2 splices for the +12v power wire for the coils, one splice feeds 2 coils and the second one feeds one coil... is this going to send you on a wiring wild goose chase, I do not know. If you have a piercing probe you can put a test light on the +12v wire for the 3-6 coil and see if it goes out while driving. If it does then you are going to have to open the loom and find out where the open is. A basic wiggle test on the wire harness isn't a bad idea either.

I found this on you tube it is worth a look...
https://www.youtube.com/watch?v=gBxaEfkWjvA

 

Yes, I read your post and I wrote my reply based exactly on what I read. Maybe you should read it again. You probably meant to use the word "rebuilt" instead of "new". I don't know the condition of the engine that was rebuilt, nor do I know to what extent new Toyota parts were used in rebuilding your "new" motor, or competency of whomever did the work, or the quality of whatever parts were replaced.

If the shop that did the work is a reputable rebuilder and warranted the engine, then take it back to that shop and request the problem be repaired. Could be that one of the parts that was replaced is defective.

 

Thanks Glamisman wiring harness is the next investigation, at this point its the only place left to look and toyota for some reason doesn't solder any of the splices in their harnesses

 

Perhaps you shouldn't reply to posts when you have nothing to offer in the way of relevant advice..
And you need to throw attitude when it's pointed out to you that almost all the info you said wasn't in my post is actually all there, its says rebuilt not that that makes any difference., troll elsewhere

 

Does anyone have the torque spec for the intake manifold or plenum? For a 1999 v6 3.4

 

Anyone out there know how to read ignition waveforms?

 

rereading and rethinking... have you put a vacuum gauge on it? follow my thought process, if you have a vacuum gauge on the motor and an inductive timing light on #3 or #6 whichever is easier... (waste spark ignition) and the vacuum gauge drops when the timing light flashes then I think you have a mechanical problem... cam, valves, rings etc. I have never tried this but I dont know why it wont work.

 

I'm having this exact issue now. What was the solution?

 

Well new plugs/coil packs and wires fixed it for me. Was a bit stressful because I was 1000 miles into a 3000 mile trip.