I have been fighting this issue on this 04 mazdaspeed miata awhile now.

After driving a few miles & letting the car warm up the car starts Boging at about 3k rpms & gets progressively worse until the car isnt drivable.
But if i let it sit for a few min's it drives fine for a very short period of time again.

At start up & before the car warms up the car runs just fine at normal driving condions & at wide open.

we recently rebuilt the motor & have had issues ever since.
Things that were replaced:
Crank, rods, pistons, rings, bearings, seals, oil pump, oil pan, timing belt, Turbo, head gasket, Coil packs, spark plug, crank position, cam position sensor, boost solenoid, clutch Fuel pump, Fuel Filter, fuel relay & im sure im forgetting some things.
I have even gone as far as to drilling a big hole in my Cat to relieve pressure

Here is a Video i made showing whats going on.

has anyone else had this issue?

 

Now that the Temperature has dropped it now takes longer for the car to start acting up.

 

Is it running the stock ECU or an aftermarket ECU such as Megasquirt?

One thing to consider: If you are running a stock manifold, it has butterflies that are vacuum activated, in such that they close when there is high vacuum in the manifold. This causes the air to "tumble" and was installed to help with emissions originally.

The switchover point is 160 degrees and 3,500 rpm. In other words, if you engine is below 160 degrees AND below 3,500 rpm, the vacuum solenoid is open allowing the vacuum from the manifold to pull the butterflies closed. once it gets above 3,500 rpm it closes the solenoid preventing the butterflies from being affected by the vacuum. That is in my understanding, how it works.

One thing you can do to test, is to unplug the VTCS solenoid and wire the butterflies open. See if it still has the problem. If it does, that the butterflies are likely not your problem.

 

It is running a factory msm ecu.

 

That video doesn't seem like the issue I am describing btw. That is just strange.

 

sorry i didnt see the rest of your comment.
The temp & rpms rang sounds about right. but im not sure what i could of done to mess with the butterfly's. maybe neck a wire or get a vacuum line wrong? i would have to look more into this.

 

I am beginning to think it's not the butterflies, but give it a try anyhow. We will see if anyone else chimes up on stuff.

 

so you did not have this issue before rebuilding the engine and replacing all these parts?

i would try to swap back the coils, wires, cam and crank sensors, it should be one of those that causes this issue. most likely cam angle sensor or coils.

i had a similar problem on my 99, i replaced the cam and crank sensors, but the problem remained. so i am fairly certain it was the coils

 

No it was not doing this before the rebuild. But when I first finished the rebuild It had a issues starting, so I replaced a few things like the coils, cam & crank sensor & fuel relay. ... It ended up being the position of the crank angle sensor.

since then I have turned all those items back to the origanl parts except for the crank.

 

I'd be curious to see what a good OBD tester says is going on. (the kind that reports more than just readiness states)

 

It would be nice to know what the vac & psi are at when this is happening. Possibly related to that, maybe butterflies like mentioned but the fluttering (lol) sounds like it could be vac related.

The miss sounds crank/cam related as it's stuttering per rotation or new signal to either one of those sensors.

 

Can't be IM related. The stutter is a hard cut type, not a bog. It looks like momentary fuel/spark cut.

probably related to cam/crank sensors loosing sync. Or coil issues/misfire.

Is the check engine on?

I had the same problem in my 99. After a long hwy drive or an autox day. It would start cutting out like that. Always thought it was the coilpack. Even replaced cam/crank sensors and issue still persisted.

 

Well i reinstalled the old Crank position sensor. ....& It ******* worked!
She isnt bogging anymore.
seems most of the new parts you buy now a days & just Garbage.

 

congrats!!

its always a million parts swap, to find one little thing that causes all the chaos.

 

thanks everyone