Car cutting out when changing Gears

[CheekyWankel]

Hi guys,

My 8 appears to be cutting out when gears are changed down. The revs are dropping too much by the sounds of it

It hasn't been used for a few weeks and the last time it was used it had a compression test and was revved cold.

Could the comp test have affected anything? I'm due to go to a meet tonight but I doubt I'll be taking this heap at this rate

Thank you.

[PeteH]

I think this is hard to comment on without understanding exactly what you mean.

Does the car idle normally?
If you hold the revs at (say) 4000rpm, then lift off the throttle, will the engine return to a normal idle?
If you are driving along and you lift off the throttle (still in gear) so the car starts to slow down, and then you apply the throttle again, does the car start to accelerate again?

When you change down through the gears the engine shouldn't have enough time to stop. In fact, ideally you should blip the throttle to increase the engine revs when changing down. So I'm not sure what you mean by "the revs are dropping too much".

[Nerdstrike]

Is this the "forgot the idle trims" problem? Did it have its battery disconnected recently?

[CheekyWankel]

A bad connection on the clutch switch can cause some strange behaviours but some clarity needed on what exactly is happening.

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[New Duke]

Is this the "forgot the idle trims" problem? Did it have its battery disconnected recently?

Could well just be that.

[CheekyWankel]

Sorry for the bad description, had to go by what my mum text me.
Just clarified with her and the revs just drop to zero when changing down, only happened 4 time so wasn't at every change.

It didn't idle well in traffic and revs dropped to zero. She had to keep them up.

The battery hasn't been touched. Spark plugs have been removed recently.

[CheekyWankel]

Is this the "forgot the idle trims" problem? Did it have its battery disconnected recently?

Could well just be that.

Could an ECU reset help perhaps? No harm in trying it is there?

[CheekyWankel]

Yes try it, and no it won't do any harm.

[CheekyWankel]

I did an ECU reset and now the car idles and changes gear without issues. Thank you for all your input my dudes

now if only an ECU reset would sort the rust out too!!

[CheekyWankel]

The fact that it needed a PCM* reset indicates that something went wrong, at some point before the stalling became an issue.

Something caused the PCM to start using a configuration that was inappropriate.
Potential causes include;
- corruption of the NVRAM by jump starting
- loose battery connection, or other wiring fault
- bad signals from one of more sensors; IAT, MAF, O2, ESPS, etc
- poorly performing ignition system
- poorly performing fuel injector(s)

It's (almost) impossible to identify which was the culprit in your case, without a Tardis to go back in time, but if it happens again you need to get to the root-cause before you just reset the PCM.

*PCM = Powertrain Control Module, so much more than just an ECU (Engine Control Unit)

[CheekyWankel]

Thanks, other than being fiddled with for a comp test I have no idea what it could have been. But yes if I happens I'll take a look into it before trying to sort. Fingers crossed that it'll be fine... For now...

[CheekyWankel]

It might just be "one of those things" in which case enjoy while you can

[CheekyWankel]

The amount of things this car has done differently for a day or two and then going back to normal is pretty concerning.

I'm pretty sure he's on his last legs, really hope not though love this car so much. Will do anything to keep it going.

[SeeJay]

Leanne,you have more than one RX8..as far as I know..so you're still good to go

[CheekyWankel]

Leanne,you have more than one RX8..as far as I know..so you're still good to go

Haha I know but favouritism and all...

Nah they're both great in their own ways of course, and my MX-5 was an absolute dream with today's weather.

[CheekyWankel]

He's doing it again.

Will get it hooked up and tested. But I'm starting to come to the end of tether with it's constant issues...

[ChrisHolmes]

Check if you have a loose battery terminal.

[Essex2Visuvesi]

Is this the blue one again?

[GreySilver Beast]

That'll be the problem then, should have bought a red yellow one

red-blue4.jpg

[CheekyWankel]

someone at work has suggested that I leave the battery disconnected for 4 hours so the car basically resets itself. I'll give that a go and if that doesn't work then I'll turn to my mechanic. Gotta try those janky repairs first!

[CheekyWankel]

Is this the blue one again?

nah, the Red 231 that I actually use

[PeteH]

Ah. I think we probably assumed you had done that when you did your ecu reset. Disconnecting the battery is part of that process. You don't need to disconnect it for 4 hours! It probably happens instantly, but a couple of minutes is fine.

Do a search on here for ecu reset. There is a great guide somewhere on here....

[CheekyWankel]

nooooow he tells me

gonna go hunt for that thread now, thank you

[Dazza44]

https://r.tapatalk.com/shareLink?url=ht ... are_type=t

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[CheekyWankel]

https://r.tapatalk.com/shareLink?url=ht ... are_type=t

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Thank you so much!