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ultimass

Original Poster:

59 posts

39 months

[news] 
Thursday 30th August 2012 quote quote all
The idle is playing up on my LS7. Recently at no particular time (it has never done it until the engine is properly warm) it 'sticks' at various levels - around 1500, 2000, 3000 rpm. After a while it will go back to normal(1000rpm)and then 'stick' again as it did this evening.

Even if you blip the throttle, it makes no difference.

When it is not idling properly, the engine is not as smooth and the pickup is poor.

I have checked the linkage and butterfly's to see if it is sticking anywhere, but all is ok.

The ECU is Motec.

Any ideas on what could be causing the problem?

Martin.




Steve_D

9,181 posts

138 months

[news] 
Thursday 30th August 2012 quote quote all
What throttle body is it and is it electric fly-by-wire?

Steve

Storer

2,687 posts

95 months

[news] 
Thursday 30th August 2012 quote quote all
Lots of things to check.

Things that spring to mind are(in no particular order):

Inlet manifold bolts all correct torque.
Engine loom earths all good.
Plugs all tight (a bit of connector spray may help too).
Check your engine loom wiring and make sure none has got too close to something hot.

If it is heat related then it suggests that something, like a sensor or it's wiring, is breaking down when hot. Probably a process of elimination.

Good luck.



Paul

738 driver

1,195 posts

73 months

[news] 
Thursday 30th August 2012 quote quote all
Air leak......... vac pipe (or bung) loose, split, missing ???

F.C.

2,993 posts

88 months

[news] 
Thursday 30th August 2012 quote quote all
738 driver said:
Air leak......... vac pipe (or bung) loose, split, missing ???
+1
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Steve_D

9,181 posts

138 months

[news] 
Friday 31st August 2012 quote quote all
If it were an air leak you would expect it to be there all the time not random. Nore would you expect it to pick different revs to run at.
Temp related I could understand particularly with the plastic intake.

More likely a failing sensor. A data log from the ECU should find that.

Steve

macgtech

759 posts

39 months

[news] 
Friday 31st August 2012 quote quote all
Steve_D said:
If it were an air leak you would expect it to be there all the time not random. Nore would you expect it to pick different revs to run at.
Temp related I could understand particularly with the plastic intake.

More likely a failing sensor. A data log from the ECU should find that.

Steve
All of the above, but I would guess an air leak somewhere.

Are you running lambdas, and if so in what mode? The other one that we have found is next to useless on the LS7's is the MAP sensor. I think the other sensors would simply throw up errors constantly on the ECU - are you able to read any fault codes?

andygtt

7,159 posts

144 months

[news] 
Saturday 1st September 2012 quote quote all
do you have logging enabled in the Motec? its 195 plus vat and will allow you to review what the ecu is seeing rather than trying to find it while its running and thus changing constantly.

ultimass

Original Poster:

59 posts

39 months

[news] 
Tuesday 9th October 2012 quote quote all
Thanks for all the info.

I have checked as far as i can for leaks and hot spots etc. and everything seems fine.

not had the problem for a while then on Sunday it happened again twice.

spoke to the guy who mapped the car for me and he thinks it may be the throttle position sensor and advised me to replace it. i have taken it off but there is very little identification only a 'c' symbol in a circle (like a copyright symbol) and the numbers 1107. Can anyone identify it and where i can buy one from in the uk?

Thanks,
Martin.

Storer

2,687 posts

95 months

[news] 
Tuesday 9th October 2012 quote quote all
Give Partsworld Performance http://www.partsworldperformance.com/ a call and talk to Laura.

They are usually very helpful.


Paul

ROWDYRENAULT

813 posts

94 months

[news] 
Wednesday 10th October 2012 quote quote all
Martin: When the system goes into this fault mode again try the following: Go to the sensors page on the motec, look at throtle posistion on the screen as you move the throtle if it is not indicating a steady movement, or if you see no change in throttle posistion your Throtle posistion switch is at fault. It is a snap to change the TPS but you will need to reset the motec. If you need instructions on how to do that E mail me and I will send you my file. Lee
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