Mystery 3000 RPM miss.

So a while ago, I discovered that, when ever my 1999 3.4 V 6 engine hit around 3000 RPM, regardless of what gear it was in, the engine would immediately cut out and the engine was unable to pick up Revs beyond 3000. It would go that far and no further with a heavy miss preventing any increased engine speed. Up to that 3000 limit, the engine seemed to pull well in all gears, although it did seem like fuel consumption had risen. I asked around on another forum and one suggestion was that there supposedly is a part on the crankshaft that acts as a trigger for a sensor that gets broken when a bolt it's connected to isn't torqued to its full 300 lbs., likely happening during a water pump/timing belt replacement. Also, I remember looking up the part and found there was a repair part available for just this kind of break and cost the princely sum of 4 whole dollars. Not wanting to do that much involved work, I took it to my local Toyota service department and a week, numerous things tried and $700 later, nothing had changed. I asked about that broken piece that was mentioned on that forum and was told by the toyota operator that the tech said it wasn't anything like that. They supposedly checked all the likely suspects; plugs, spark plug cables, coil packs, injectors, and they cleaned the contacts on the ECM. But nada. From what little I got from the tech, it seemed like it was never taken for a test drive, just hooked up to diagnostic tools. Supposedly my "case" had been sent to some group of expert mechanics with Toyota but they never called me back. So, any thoughts? I've noticed my water pump seems to be leaking and I'm gong to replace it and was thinking this might be the time to look into that repair piece only, when I look in my Haynes manual, all I can see in the way of sensors in that vicinity is an anti knock sensor. I'm at a loss. Thanks in advance for any and all help!

 

Typically this is a crankshaft or camshaft issue or wire harnesses issue to these sensors,
When this happens it’s the same type feeling of hitting the rev limiter and sometimes the rpm needle jumps around when it hits that spot.

 

What do you mean by 'cut out'? That term normally refers to a loss of secondary ignition, but your description makes it sound more like the engine is hitting a rev limiter. Do you have a 'Check Engine' light on? What code(s) did the dealership pull?

 

Thanks for the comments! If it were crankshaft or cam shaft issues, do you mean that there's something wrong with related sensors that prevent it from providing the correct info to fire at the right time? If that is the case, is what I was told about something coming loose as a result of under torquing a nut with a water pump replacement a possibility? As for cutting out, it really does feel like it's hitting a rev limiter, but it's being limited because it feels like it's got a heavy electric miss or fuel flow being cut off. Unfortunately, while it did throw a code way back when, the guys at the Toyota dealership said that the code it come back with was not specific enough to help lead to figuring out the problem or that it caught another problem but not the one causing the major problem. And to make things even more fun, it quit throwing a code even when it was run through a process of resetting the computer by me following the process in driving the truck to clear things up for a new code to be caught. Again, thanks for giving your expertise a shot a this thing. It's kind of driving me crazy. I've already cleaned and replaced a couple of the sensors upriver from the injectors with no change. I just wish it would throw the code again.

 

You need a good quality scan tool with live data capability, and someone with the knowledge to understand the data. I suspect that a few minutes driving under the "Customer states..." conditions will give you a fairly solid starting point. This doesn't sound like a CMP/CKP issue to me; typically those will cause issues all over the powerband and should DEFINITELY set a MIL. I would normally like a bad ground for this, but the consistency that you're indicating doesn't make that feel good either. It sounds like it should be a fairly straight-forward issue to troubleshoot with the right tools and experience, but unfortunately, not one which is easily diagnosed over the Internet....

 

Does it do it at part throttle or only heavy throttle? Reason I ask it could be a fuel issue, like low fuel pressure if its heavy throttle only.

I had the cut out at 3000 rpm sometimes, and it was exactly like the rev limiter - as if truck was shut off and it did not have to be full throttle. I replaced the crank sensor and seemed to fix it but since it was intermittent not 100% sure.

 

Could also be low fuel pressure, as mentioned, or a plugged up cat converter.

 

sounds kinda like limp mode, do gen1s have a limp mode?

 

Thanks again all for the help! I tried the cheapest replacement I could, even though, after spending $700 at the local Toyo dealership they couldn't find anything and I believed that all their high tech scanners should have caught what it was. I replaced the crankshaft sensor. Runs like new now. Next up, water pump replacement.