M37S GTM SC Stage 2 - falling engine speed
 

My car is Infiniti M37S with 7AT and has installed GTM SC Stage 2. There is also custom exhaust without catalytic converters.

I have noticed falling engine speed to 500 rpm when car is moving at very low speed and I push and release the accelerator pedal - especially when I drive in traffic jam. It is seen on video:

M37S - obroty - YouTube

It do not occur when engine is cold. I have checked vacuum lines, BOV.

Is this a common issue? What should I check first, next?

Thanks,
Robert

Are you using the can tune supplied by GTM or a custom one?
I had some what a similar problem, my idle would drop down to 500RPM when at a street light and was on the GTM tune. Had it looked at by a local tuner and we had to tune the fuel to the MAF and dial in those settings.

I have the custom one.
I do not have problems on idle - engine speed is always correct. It happens only during driving at low speed. I suppose it happens when torque converter is not locked.
Now I have driven 10.000 km after SC installation. About 2.000 km ago I installed custom exhaust and issue with engine speed appeared at about the same time - but I'm not sure now.

Thanks,
Robert

get it retuned? not the same issue as you but when i messed with my stock exhaust my idle started acting funny and started dropping. ended up cleaning out the throttle bodies which solved my idle issues.

Some things to look into: Make sure that you don't have an exhaust leak and get your tune adjusted if it persists.

+1 on exhaust leak

Thanks.

1. The throttle bodies were cleaned up.

2. After the custom exhaust were installed we did retuning - fuel and ignition maps were changed.

2. The custom exhaust is 2 x 2,5" with no catalitic converters and six customs mufflers. I do not think that there are leaks, but it has less back pressure than OEM exhaust.

3. I had connected Osiris and did not notice any strange when this issue occurs or I did not know on which parameters should I look.

Could you tell me which parameters should be logged or changed?

I'm not too savvy with tuning, but your tuner should be able to make some adjustments that can potentially fix this. I still also say check your exhaust for leaks. I've had a GTM SC kit since 2011 and have encountered some exhaust leaks that have caused similar issues.

Grabba,

If you can send us a log of when the problem occurs and we will try to see if it is a tunning issue.

Who tuned the car for you?

-George

George, thanks. I will prepare logs and send it to you.

I have tuned ROM from you (GTM) and additional one from Coobcio Garage (Poland). On both this issue occurs.

Coobcio's ROM is based on yours - fuel and ignition maps were changed. On yours I have 521 hp, on Coobcio's 570 hp.

Grabba,

This issue only occurred once you changed exhaust, was anything else changed around the same time? Have you tried putting the OEM exhaust back on just to rule out if the exhaust is somehow related.

I can't see how an exhaust would create this issue, especially at such a low load site.

-George

No, nothing else was changed. Maybe weather?
No, it could be rather difficult because I don't have catalytic converters now.
It is strange to me too. I did reflash ECU with GTM ROM and went for a short ride.

There is log from this ride: https://drive.google.com/file/d/0B-5...it?usp=sharing

At the beginning the issue occurs 2 times, later engine speed falls too but not to 500 rpm because speed is higher. From 1:18 to 1:40 this issue occurs several times at speed about 15 km/h.

Thanks, Robert

George@GTM, did you see the logs?