Stumble At 6k Rpm

[takeaflyingleap]

I have a strange little problem. The engine runs great, however it stumbles at 6k rpm. It's a very short stumble. Almost like when a rev limiter kicks in. It only happens at 6k, every time, no matter what.

Any ideas?

TIA, Neil

[SKperformance]

change your rotor and cap

[takeaflyingleap]

Brand new cap, rotor, Bosch platinum +4 plugs (less than 1k mi) new wires (less than (500 mi). Checked fuel pressure, and injector resistance all check out ok. I also replaced/added: Knock sensor; pcv; cleaned and checked egr valve; ported and polished intake and heads; cold air intake; all new top end gaskets; checked valve clearances.

The thing that I don't understand is why it stumbles at exactly 6k rpm. I have had an eratic miss that happend at almost any rpm on another car. but this one happens at only 6k rpm. No miss from 1k to 6k and no miss from 6k to 7k.

TIA,

Neil

[justin97]

Brand new cap, rotor, Bosch platinum +4 plugs (less than 1k mi) new wires (less than (500 mi).  Checked fuel pressure, and injector resistance all check out ok.  I also replaced/added: Knock sensor; pcv; cleaned and checked egr valve; ported and polished intake and heads; cold air intake; all new top end gaskets; checked valve clearances.

The thing that I don't understand is why it stumbles at exactly 6k rpm.  I have had an eratic miss that happend at almost any rpm on another car.  but this one happens at only 6k rpm.  No miss from 1k to 6k and no miss from 6k to 7k.

TIA,

Neil

←

fuel filter?

[93ls400walt]

Brand new cap, rotor, Bosch platinum +4 plugs (less than 1k mi) new wires (less than (500 mi).  Checked fuel pressure, and injector resistance all check out ok.  I also replaced/added: Knock sensor; pcv; cleaned and checked egr valve; ported and polished intake and heads; cold air intake; all new top end gaskets; checked valve clearances.

The thing that I don't understand is why it stumbles at exactly 6k rpm.  I have had an eratic miss that happend at almost any rpm on another car.  but this one happens at only 6k rpm.  No miss from 1k to 6k and no miss from 6k to 7k.

TIA,

Neil

←

fuel filter?

←

Could be one of the coils with malfunction at high output.

[Toysrme]

What's:

ignition timing

Resistance of the coil

compression (on every cylinder w' the engine warmed up)

Be ready to ditch the spark plugs & wires you just bought too.

[takeaflyingleap]

Compression is good. Can't remember the numbers off the top of my head. Why do I want to ditch the plugs and wires?

[Toysrme]

Cuz most replacement plug wires are very low quality. (Falling under the thermostat rule. 25% failure rate 'cause they are pre-damaged, or installed incorrectly). I'm just guessing you bought whatever is @ the auto-store instead of paying Toyota around $100 for the OEM wires, or other high quality wires. I may be wrong there, but ya know.

Bosch platinum plugs (& American brand plugs in general) do not work well on Denso ignition systems. They simply require too much energy to spark well. They tend to loose lots of spark within 5, or 10 thousand miles. Given a year of running time, even the cheapest plugs out of Japan kick the crap out of Bosch platinum (Get's worse with multi-electrodes).

The only way to get the high energy plugs to work long term without changing to big coils is to mod the stock coils to charge longer. That's actually easily accomplished by making the dwell time longer. Cost a couple dollars & a half hour to do. The problem is the style of coils Denso uses in most Toyota passanger engine's have been known to burn up if you over do it & the only way to check it is with something that can read the dwell.

Maybe I'll write how to do it in the future. Mine's been done on & off since '04. More spark is fun LoL! (When I first started playing with my SMT-6)

Timing

Coil

Vacuum leaks

If everything else under the sun TOK's. Ditch the Bosch plugs for something NGK, or Denso plugs. I would do plugs after testing everything else possible.