Recently taken delivery of a new CX 5. I believe there is a problem with the engine speed upon start up. On several occasions the car starts in a normal way and tick over at around 850 rpm but then, on others, it will race up to around 1800 - 2000 rpm. I reported this to the dealer and delivered the car to them for investigation only to be told all is fine. I can accept "there are no codes showing" after a diagnostic check but, nevertheless, Mazda can't give me a suitable explanation for the differing engine speeds which occur whether the engine is hot or cold. Surely, the car is designed to tick over at 850 ish on start up regardless of the "outside" temp. I should add that after about 20 or 30 seconds, the engine speed settles to normal tickover. Any advice would be most welcome thank you. Dave
Engine idle speed
- Thread starter Dave Bew
- Start date
- :
- 2021 CX-9 Sig
- :
- 2021 CX-5 GT
No, that is normal. That engine needs to warm up and revs quickly at warm up to ensure a shorter warm up time.
When the engine is cold, my engine starts at ~1,500-1,800 RPM and within 20 seconds drops to ~ 1,000 rpm. When fully warm it idles at 650 to750 rpm. The engine control module is programed that way to heat up the catalytic converter quickly to reduce pollutions. Ed
Mine does the same, and its certainly not normal.
I've complained to two different dealers about it and even Mazda.
Only to get fobbed off with a very plausible reason for why it does it.
I could see the logic if it was repetitive in its action, but its not, hot or cold it makes no difference, now and then it revs its balls off at 1900rpm.
I use to program PLC's as part of my job, so setting conditions to result in an action was common practise, that's why the high rev issue isn't normal, as the conditions for it over revving are random, not repetitive.
My car actually rev high on start up in SUMMER, and others have also reported the same scenario.
Now is colder only occasionally does it rev high on start up.
I'll find the email and post it.
I've complained to two different dealers about it and even Mazda.
Only to get fobbed off with a very plausible reason for why it does it.
I could see the logic if it was repetitive in its action, but its not, hot or cold it makes no difference, now and then it revs its balls off at 1900rpm.
I use to program PLC's as part of my job, so setting conditions to result in an action was common practise, that's why the high rev issue isn't normal, as the conditions for it over revving are random, not repetitive.
My car actually rev high on start up in SUMMER, and others have also reported the same scenario.
Now is colder only occasionally does it rev high on start up.
I'll find the email and post it.
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Case Reference: 1-517969912
Thank you for your recent email.
Having discussed your concern with our Technical Department, I can advise the following:
High idle speed is a normal function of the SkyActiv Diesel engine on start up, and is not related to any PCM updates; this has always been a feature of this engine.
After a cold start, the regulating valve and the wastegate valve are fully open to enable the exhaust gas to flow through the turbochargers without losing much exhaust gas heating capacity. Also the VVL mechanism slightly opens one exhaust valve per cylinder during intake stroke in order to recirculate a certain amount of high temperature exhaust gas back to the cylinder.
This is for early activation of the catalytic converter and improved exhaust gas purification. This does not indicate defect of the parts.
Operating Requirement
1. Water temperature (ECT) at engine starting: from 15 to 32 degrees Celsius.
Intake air temperature (IAT) at engine start: from 15 to 35 degrees Celsius.
Barometric pressure at (BARO) at engine start: from: 91 to 200 kPa.
2. Gear position: P, N, D with the engine idling (Accelerator pedal not depressed)
This is mentioned in the owner’s manual
Owner’s Manual
This concern is mentioned in the O/M “When Driving Start/Stop Engine” as follows:.
After starting a cold engine, the engine speed increases and a whining sound from the engine compartment can be heard.
This is for improved exhaust gas purification and does not indicate defect of the parts.
In closing, I trust the above information clarifies your Mazda CX-5 is operating as intended.
Yours sincerely
Jon Haywood-Smith
Regional Customer Relations Manager
Thank you for your recent email.
Having discussed your concern with our Technical Department, I can advise the following:
High idle speed is a normal function of the SkyActiv Diesel engine on start up, and is not related to any PCM updates; this has always been a feature of this engine.
After a cold start, the regulating valve and the wastegate valve are fully open to enable the exhaust gas to flow through the turbochargers without losing much exhaust gas heating capacity. Also the VVL mechanism slightly opens one exhaust valve per cylinder during intake stroke in order to recirculate a certain amount of high temperature exhaust gas back to the cylinder.
This is for early activation of the catalytic converter and improved exhaust gas purification. This does not indicate defect of the parts.
Operating Requirement
1. Water temperature (ECT) at engine starting: from 15 to 32 degrees Celsius.
Intake air temperature (IAT) at engine start: from 15 to 35 degrees Celsius.
Barometric pressure at (BARO) at engine start: from: 91 to 200 kPa.
2. Gear position: P, N, D with the engine idling (Accelerator pedal not depressed)
This is mentioned in the owner’s manual
Owner’s Manual
This concern is mentioned in the O/M “When Driving Start/Stop Engine” as follows:.
After starting a cold engine, the engine speed increases and a whining sound from the engine compartment can be heard.
This is for improved exhaust gas purification and does not indicate defect of the parts.
In closing, I trust the above information clarifies your Mazda CX-5 is operating as intended.
Yours sincerely
Jon Haywood-Smith
Regional Customer Relations Manager
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It's very unpredictable.
Mine very rarely revs high when I start the engine parked in my garage but often does it when I start my car to leave work when it is parked outside. It seems to do it more often in warmer weather too. Basically it seems completely random to me, unless there is some voodoo sensor which determines when it does it, then I'm at a loss to explain it.
PS, I still programme PLC's as part of my job, so have the same reasoning.
Mine very rarely revs high when I start the engine parked in my garage but often does it when I start my car to leave work when it is parked outside. It seems to do it more often in warmer weather too. Basically it seems completely random to me, unless there is some voodoo sensor which determines when it does it, then I'm at a loss to explain it.
PS, I still programme PLC's as part of my job, so have the same reasoning.
Exactly. It is written in the manual with an explanation. Absolutely normal.
It's also not about the outside temperature. It is about the engine temperature. If your car has been sitting (say overnight) the engine is cold no matter how hot your environment is (unless you live on the sun.) If you've just driven to the market and 15 mins later get back in the car, the engine will still be warm.
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I can assure you I can start the engine cold with normal tick over, set off with the blue cold engine light up.
My car and Dr Watson are both diesel, and we have the same random fast revs start up.
If a cold engine instigates a fast tick over around 1900rpm, then it should happen every time, not occasionally.
Yes I read the manual, not all of it is correct.
A lot of it isn't applicable either, to UK cars.
Section 6 mentions disconnecting the battery among other things relating to the battery.
All of which according to two separate dealers is inaccurate, they say a istop battery should NOT be disconnected, and cannot be fully charged with out a special high voltage charger, when I say high they mean around 17 volts.
I had a 2L petrol years ago, that would always start at high revs when cold, typically at around 1500rpm, then quickly settle to a fast tick over until warm.
But it would do it every time it was cold, not when it felt like it.
Looked at my 2.5L this morning and it started at 1500rpm. There is a good reason for this. The CX-5 is the first production car to use Tri-Y (4-2-1) headers. No one has done it before because by the time exhaust gets to the catalytic converter its to cold to light the cat. Mazda solved this problem by injecting raw gas into the exhaust on cold start to quickly heat up the header and cat. The Tri-Y header is why CX-5 can run 13:1 compression on 87 octane gas and has a very low torque peak of 3250rpm. High idling on cold start is a small price to pay for best mpg, best power, and best low end torque.
I wouldn't expect a regen to start with a engine showing the blue cold engine symbol?
who needs a stinking manual? (silly)
Nope, it's easier to point the finger at Mazda and then go through all the hassle of taking the car to the dealer and then posted it on a forum.
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