pineymudder

Ok guys heres what i have. 91 ext cab 5 speed. 96 4runner 3.4 auto swaped in. I kept 5 speed. I have 1000 miles on it, runs great except after 3000 rpms. Has slight miss or stumble. I changed plugs (dual ground), wires, cleaned maf, new air and fuel filter. Lower gears have less problems but if engine under hard load it does it too. 5th gear at 1500 rpm if i try to accelerate i feel it then too. I tried everything i can think of. Let me know what u guys think. Thanks
Jason

SacRunner

fuel pump?

Could this be an issue with "tricking" the ECU to think its in neutral? I could see the engineers at Toyota building in some sort of fail-safe or governor to keep the engine from revving too high in neutral. I have no idea on this one, and I haven't seen anyone else complaining about it. (and of course this doesn't account for the issue with 5th gear)

pineymudder

Well its not nesecarily a fifth gear issue. I just used that as an example. Any time the engine has high load it does it. Say someone in front of u is turning and u slow down a little slower than u should b for that gear and u hit gas it stumbles. Or any gear after around 3000 rpm it stumbles. It drives fine as long as i dont punch gas hard.

89934runr

First thought was a lean condition by either fuel pressure, an air leak, etc...but I've seen this on a few customer vehicles (and my own 3.4 swap)- pull the coils off & check the boots for any arcing through the boots...U will see a small amount of white or gray residue. When I first dyno'd my swap, I had a miss that is exactly as U described.

Good luck; Keep thinking ignition & you'll find it.

pineymudder

I did check secondary coil resistance when i started and i had no continuity in one of them. I pulled it apart and its just a metal clip to a metal spring. I had to remove spring and wire brush both to get connection back. I guess ill try and replace coil boot things. Do they come with spring and clip? I hope so. Thanks for the replies.
Jason

pineymudder

well..... i changed the spark plug coil on boots. (even though mine still tested fine with ohm meter) truck runs awesome! no miss no sputter no nothing just great acceleration. thanks again guys.

89934runr

Glad to hear you're running better.

As much as I love using my DVOM for ohm readings, sometimes there is no better test than an engine under full load (higher cylinder pressures = more voltage & current required to jump the spark gap). Ignition components have a way of lookinging one way (ok) at ambient temps without a load on them, then they become a different beast under heat & engine load. On those plug boots, all it takes is a tiny pinhole. BTW- did you use any dielectric compound on the end of the plugs & at the coil contacts? It will help prevent the ionic corrosion that typically happens in coil on plug (COP) systems.

My guess is that if you had a KV meter on it under load, you would see the dropped cylinders (like a squigly line on a dyno graph). Toyota's misfire monitor doesn't do so well on these engines... we had to completely pull a plug wire to get it to recognize a dead cylinder.

Sorry for rambling.

pineymudder

Yes i did use die electric grease on all boots and wires. I didnt notice if computer recognized the miss cause i used an auto comp in my 5 speed truck so i have constant engine light for now. ( at least till aug 2014 when i need emission test) i have been checking obd 2 every once and a while to make sure i have no other codes.

89934runr

Although this isn't a 3.4 coil, this is basically what happens to them. This is what a customer's 02 Pathfinder had on Saturday- misfire under load, runs smooth most of the rest of the time. Code showed P0303 (misfire #3). Turns out, it was a coil firing through the coil/plug boot. If you look closely at the edge of the boot, it left a trail of ionized deposits on the boot- there is a small pinhole through it at that spot.

Sorry for beating a dead horse Pineymudder; I'm glad to hear your issues went away.

pineymudder

I did notice slight marks like that but mine were at bottom of boot long past spark plug connection closer to the head side. Also the boot was very stiff as if heat damaged it. The others were ok i guess. I changed them all to b sure.