Flat spot/hesitation 4-5k rpm?

[dac69er]

OK when you did the 20 pedal stomp you would have cleared any fuel 'learns' as these adjusted values are learnt over time / milage

I'd say either there's an exhaust leak on the exhaust affecting the O2 sensor reading or the O2 sensor is faulty

There is no exhaust leak I can find. Sounds fine and I can't feel any leaks.

The O2 sensor is a possibility. I will get hold of one and see if that helps. I don't get any DTC codes though and it is literally only at that point in the rpm range, worse when part throttle and I go through that range slowly which does point more towards with the inlet valving control, but that all appears to be working as it should!?

[warpc0il]

If the front O2 sensor is giving "off" readings then that could definitely be the cause. The problem is compounded if you're checking live data via OBD because you'll be seeing the same as the PCM, so it will appear to be correct.

I've seen this coughing under load situation where someone has fitted a replacement, non-Mazda part, even though they were convinced it was from the oem source.

Mazda themselves couldn't get the 6-port and 4-port to run properly with the same sensor and had to use two different ones, while all their principles would be pushing them to harmonies parts.
But aftermarket suppliers quote their single unit for both engines....

[dac69er]

If the front O2 sensor is giving "off" readings then that could definitely be the cause. The problem is compounded if you're checking live data via OBD because you'll be seeing the same as the PCM, so it will appear to be correct.

I've seen this coughing under load situation where someone has fitted a replacement, non-Mazda part, even though they were convinced it was from the oem source.

Mazda themselves couldn't get the 6-port and 4-port to run properly with the same sensor and had to use two different ones, while all their principles would be pushing them to harmonies parts.
But aftermarket suppliers quote their single unit for both engines....

As mentioned, it's not under load. With increased load, it is less prevalent. Light throttle is where it is worst.

Does anyone know the part number for the 6 port pre-cat sensor?
Is the DOX-1449 sensor for the 6 port engine? Everywhere I look it's the same sensor like you said. Even genuine sensors are hard to come by

[350matt]

Yes the DOX1449 is for the 6 port / 231 engine

i've run one for over 20K miles and its fine and a damn site cheaper / readily available than the OEM one

[warpc0il]

That's the true DENSO part # but there are many fakes, some in convincing DENSO packaging, plus many that use the reference.

Would you trust your engine to this? https://www.ebay.co.uk/itm/365471898522

It's the same minefield as ignition coils, spark plugs, etc. because of the high OEM pricing.

[350matt]

you can usually trust autodoc

https://www.autodoc.co.uk/denso/1665600

[Cscameron]

I have a front o2 sensor for a 231 in my bottomless box of parts if you want to try it? It's of 0 use to me (as I drive a superior 192 ) so you're welcome to it

[dac69er]

I have a front o2 sensor for a 231 in my bottomless box of parts if you want to try it? It's of 0 use to me (as I drive a superior 192 ) so you're welcome to it

I will PM you

[dac69er]

That's the true DENSO part # but there are many fakes, some in convincing DENSO packaging, plus many that use the reference.

Would you trust your engine to this? https://www.ebay.co.uk/itm/365471898522

It's the same minefield as ignition coils, spark plugs, etc. because of the high OEM pricing.

Cambaire stuff is properly cheap and nasty. I have bought that brand before and it wasn't great.
It's not trying to be anything else though to be fair.

I've been pretty lucky and not had anything knowingly fake and still found decent prices, just takes a bit longer to find

[350matt]

So all fixed now ?

[casey]

I haven't read through the entire topic, but will add another possibility, in case relevant.

I had very similar sounding issue with my car after an engine rebuild. Turned out the primary and secondary injector connectors had been reversed! Idle was a bit rough too. Once the error was corrected, the flat spot was cured and idle much improved.

Have you had any work done on the car where the primaries and secondaries may have been reversed?

[dac69er]

I haven't read through the entire topic, but will add another possibility, in case relevant.

I had very similar sounding issue with my car after an engine rebuild. Turned out the primary and secondary injector connectors had been reversed! Idle was a bit rough too. Once the error was corrected, the flat spot was cured and idle much improved.

Have you had any work done on the car where the primaries and secondaries may have been reversed?

Not had any work done on it. I do everything myself, so can say that has 100% not been touched.

Still has the issue. Took the car on a track day and it ran fine, but still has the flat spot.

I'm awaiting delivery of another O2 sensor from Cscameron to see if that makes any difference.

[350matt]

fingers crossed then