3.9 idle problem

[foxy2833]

i have 3.9 , from cold when you first turn the key it will start straight away then die out . turn the key again an it will run lovely prob 1000 rpm . leave it until it is warm an it will be fine . try to drive it an the rpm will go to 200 back up to 500 sometimes it will cut out but when its hot its fine , can anyone help . many thanks

[kiwicar]

Hi
Assuming it is and injection then the idle air valve would look like a good place to start, next possable place to look would be the throttle position sensor, if that is badly worn it can confuse the fueling a treat.
Best regards
Mike

[DaveEFI]

i have 3.9 , from cold when you first turn the key it will start straight away then die out . turn the key again an it will run lovely prob 1000 rpm . leave it until it is warm an it will be fine . try to drive it an the rpm will go to 200 back up to 500 sometimes it will cut out but when its hot its fine , can anyone help . many thanks

Check the fuel pressure. But it sounds like you have more than one fault.

[foxy2833]

hi and thanks , is there any way i can check these components

[kiwicar]

Hi
TPS is easy, disconnect it from it's plug, stick a ohm metre across it and measure it's resistance as you open and close the throttle, it should be nice and even increments as the throttle opens and closes.

Ramon on here has a whole series of test routines posted up on his website for the rover EFI, I would have a look there, I think they are really for the flapper set up, but you can probably adapt them to hotwire.
Best regards
Mike

[DaveEFI]

I don't think the TPS has any major effect on the cold start or idle.

If operating the throttle slightly helps on the cold start could be the stepper motor playing up? They're not the most reliable device in the world. Gentle opening of the throttle should show if it's simply that giving trouble or something more sinister like the mixture.

[ChrisJC]

I would go for the Idle Speed Control Valve (or whatever it's called!)

Chris.

[foxy2833]

when starting from cold for the first time i dont touch the throttle it starts straight away then dies out, turn the key again an it runs ok, but touch the throttle until the engine is warm an it surges an you think it is going to cut out . but it recovers an keeps at about 700rpm when hot drive away , the trouble is cant always wait till hot

[ramon alban]

when starting from cold for the first time i dont touch the throttle it starts straight away then dies out, turn the key again an it runs ok, but touch the throttle until the engine is warm an it surges an you think it is going to cut out .

Hello Foxy,

When an engine stalls at cold - then its usually idle mixture too weak, the torque is pants and the internal frictions due to cold oil and etc are too high, for the available torque. So it stops.

As the engine warms up so the engine requires and tolerates a weaker mixture, which is primarily controlled by the coolant temp sensor.

So you have to look for cause of a too weak start-up mixture.

Coolant temperature sensor, Stepper motor, rogue air leak (usually small) into the plenum or intake manifold, blocked breather, low fuel pressure,

The stuff on my web pages

http://www.vintagemodelairplane.com/pag ... nts01.html

is for the flapper, but some or the hot-wire components are the same, as are the diagnostics for those components and air leaks, easily adapted to your system.

[foxy2833]

hi an thanks it is hot wire 14cux

[foxy2833]

ok have had a look today a what people have been telling me , should i have a small vacume pipe coming off the housing that the idle air valve stepper motor bit is . there was one coming of this small vacume thing an it went to the rocker cover i took this an put it to the air idle valve an it ran sweet . is this right