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The mkiv Supra Owners Club

Lumpy idle


Stonkin

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Hi,

 

I have a slight issue with my idle which i would like some advise on please.

 

This problem only happens if the car has been used and it is turned off for a few minutes and then started again, ie at a petrol station filling up.

 

Tonight i drove about 12 miles,it was started from cold and drove with no issues. I stopped at a shell for fuel, when i started it to drive off the revs were bouncing between 400ish and just over 1k, when it does this the lights on the dash go dim as the revs are too low. You can also feel the car rock/vibrate when it happens. It is an auto and pulling out of the station was slightly difficult as each time the revs drop and rise the car is lurching forward a bit.

 

When it is being driven it cant really be noticed but when it does this it will normally take a mile or so for it to stop. From the garage i drove home which was just round the corner,pulled up and recorded this video to show revs and afr gauge. I spent 20 mins at home, went out in the car again and it was fine.

 

image

 

This isnt the first time this has happened. Any ideas?

 

The car is a T61 single auto with an emanage ultimate mapped by Ian C.

Edited by Stonkin (see edit history)
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Its only ever done it hen the car has been used, switched off only for a few mins and then started again. If its started from cold its fine. If its in drive and being driven its ok, but not as smooth, if your at low speed and not on the accelerator you can notice it. But after a few miles it seems to go back to normal

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Its only ever done it hen the car has been used, switched off only for a few mins and then started again. If its started from cold its fine. If its in drive and being driven its ok, but not as smooth, if your at low speed and not on the accelerator you can notice it. But after a few miles it seems to go back to normal

 

Trying to think of possible causes, so bare with me as I'm thinking aloud, i would suspect the ECU temp sensor, but as the AFRs are weak, instead of rich which is the default should it fail, same goes for air temp and lambda, the only other thing may be the EMU settings, as now the ambient temps have dropped it could be this causing the problem,

are you sure you haven got a vacuum hose come off?

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Thanks guys. How do i reset the ecu, disconnect the battery as normal for 5 mins? I presume this wont remove any of the map? Stupid question, but would rather ask than not.

 

Surely maps do not have to be adjusted when the ambient air temp drops?

 

Yes, just remove the battery connector or the ECU main fuse (personally I've always just disconnected the battery). The map on the EMU won't go anywhere.

 

The map does need to be adjusted to correct for intake air tempurature, but this should be part of the map already on the ECU.

 

It's a bit of an odd one, but agree with the points Ricky made earlier.

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I say the above because last year mine started getting leaner and leaner in closed loop until it was running at 17:1 AFRs on idle and sounding rather rough. I was stumped as closed loop is mostly unaffected by the E-Manage. So I reset the ECU to start with, and it's been fine ever since. As "reset the ECU" used to be the cry of the desperate and ignorant a while back :D I was reluctant to believe it fixed the problem, but after over a year it's been fine :shrug:

 

Hopefully it'll work for you as well.

 

-Ian

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Ive got a few places to go today, and was going to take the supra so i could note down a few more accurate numbers from the afr to see if it would help. But i think i will reset the ecu before i go, then i'll post up some numbers later to see if its behaving a bit more normal.

 

Appreciate your help.

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Hi guys, right, i left the battery disconnected for about an hour this morning and then went out in the car. I noted down some of the results but things dont seem any better.

 

First start up after reset - started at 13 and slowly rose to about 15.2

I drove aboout 2 miles and then had to stop at first shop. It was left for about 20 mins, when started the idle was between 21 and 23

After 1 minute of slow driving this dropped to 14.7 to 15

At 60 mph, 3k revs in 3rd it showed 13.7

Whilst in 3rd i did a 3/4 throttle run at 1.0 bar and it was 10.5

At WOT in 3rd at 1.4 bar it showed 9.5

Parked up at Tesco and at idle it was 19.6

1 hour later at startup it was idling at 22 - 24

 

I pulled up at a set of lights on way home and noticed if i was in neutral it showed 18.1, whilst in drive it showed 15

 

At general cruising it was always around 14-15, but soem of the results above worry me.

 

Anyone have any ideas? I think a checkup from Ryan would definetly be worthwhile.

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Hi mate that seams to be well over fueling at wot should be about 10.7 safe to 11.5 for a bit more power . and then way to lean at the other end of the scale ! need to see a data log really to get an idea of whats what . But as you don't have the software Ryan would be your next best thing , I would not do to many wot pulls with it been that rich.

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Are you running the stock airbox or aftermarket filter?

 

If you have removed the standard filter box your problem could be heatsoak from the engine. My car had exactly the same symptoms after I went single. I made a cold air box around the filter and now it is perfect.

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