HI!

When I start my 4x4 Sierra the idle speed is increased (normal
when the engine is cold), after a few seconds it drops to ~900rpm
and then it starts to rise to appr. 1200rpm and will stay there.

Cleaned the ISCV but no change. What will happen if I disconnect
the ISCV? If it drops to normal revs will it mean that the ISCV
is not working properly?
If the ISCV is okay, what else can cause this problem?

regards
Mathias

 

Connection on the ISCV????

 

HI!

What do you mean with "connection" on the ISCV?
Check the wiring?

 

Check the wires,mine were the wrong way round and had a dead transistor in my ECU

 

Even if wires were the wrong way round it would not make a difference as it is the POTENTIAL DIFFERENCE that causes the motion of the valve, ie the live is constant and the earth is pulsed as a digital signal.
Hard to see how it could be wrong way round any as conncetor is POLARISED.
A dodgy CTS will do this as if it detects a "COLD ENGINE" it will raise revs and richen mixture, the conncetors for these also play up.
Do a wiggle test whilst idling with the conncetors.
tabetha

 

You're right,if the wires are wrong way round or a faulty transistor like mine it holds the same rpm and does not drop and rise.

 

HI!

Removed the ISCV plug, but now change on revs. Where is the
CTS located?

 

May be you have an electronic problem. Hight idle speed (1.200 / 1.400 rpm) is a signal (only with L8 and P8) that something wrong on your sensors.
Do an autodiag.

Regards

Claude

 

Comming from a short drive. Idle speed is exactly 1400rpm!

Can you gibe me an advice how to do an autodiagnostic?
Is there something written in the Cosworth workshop manual?

 

COOLANT TEMP SENSOR is located at back of cylinder head underneath plenum area on 2wd but believe it may be somewhere else on 4wd, not sure if this is the CTS or the temp guage sender ?, that is in a different place to 2wd.
Worth finding to disconnect to try first as it is a no cost thing to see.
tabetha

 

HI!

Will have a look on the weekend and also check the the ecu
for error codes

 

http://www.homepages.hetnet.nl/~pete...ecu_error.html

 

take of the boost hose to inlet chamber and check the butter fly has a little clearnce with a feeler gauge had that problem myself and that fixed it

 

HI!

Sorry, I´m not 100% sure what you mean. I shall remove the boost
hose from the intercooler to the throttle valve and then?
What is a feeler gauge? You mean that your throttle valve didn´t
close properly?

 

the throttle valve should have a small gap ie 1mm or so

 

I understand, will have a look on it.

 

HI!

Wanted to make an autodiagnostic, but was not working. Was ist due
to a non original chip?

 

Hi!

Checked it on weekend. Where is this gap?

 

I have the same problem with my 1.6 CVH and this is my 3rd time.

The only thing I managed until now every time i change this starter motor it works for 2-3 months and after that story goes on.