Technical Fiat Bravo 1.2 16V idle problem

[Cro_Tom]

Hy, i have a problem with fiat bravo 1.2 16v 2000. with tartarini lpg.

Before 4 weeks car was in service, they changed head seal because seal was bad, and car was spent 1 liter water per 3-4 days.

After that service, I have a next problem with idle:

1.) When car and engine is cold (morning), car won't start normal, i need to manual add a little throttle (gas), and then car start. But then idle fals to 500-600 rpm, and car turn off.
I must add a very little manual throttle to car work normal. If I don't add a manual throttle, car every time turn off, and won't start without throttle.

2.) When car is hot and is on work temperature, idle works normal!
Car start's normal without manual throttle.
Ok, it is not every time good, in 90% car idle is good.

But when is cold, idle is bad every time!

Where is problem?
Is there a problem with idle control valve, or something else?

I was been on 2 diagnostics, but none found the problem.
They clean a idle body, reset the idle valve positions, but nothing hapened.

Same problem is and on gasoline and on lpg.

Sory for bed English!

 

[livicu]

hy, try to clean the crank/rpm sensor. it may cause the problem

 

[Oversteer]

It is possible that something was not reconnected properly after the head gasket was changed? you could have a look around the engine and all the connectors to see if anything is loose or not connected back up?

 

[Cro_Tom]

All conectors is connected, but who knows, maybe iz something disconnected and I can't see it from above the engine.

Today I drive car to service, they will change some sensors to find out where is the problem.

Yesterday I removed the inllet pipe, pipe which connects the air filter and stepper motor.
When I was watching the stepper motor flap (butterfly), I noticed that when I want to starts engine, the flap is not moving. This is why engine couldn't start on cold whitout the manual throttle.
When is engine hot, the flap still don't move, but engine starts normal just because is engine hot.

Sometimes when I turn off the engine, flap don't back to close position, but flap stay a little bit open (0,5 cm), and then engine starts normal to cold.

So, maybe is stepper motor dead, or some sensor which gives command to stepper motor to manual open.

 

[Oversteer]

Have you taken the sparkplugs out and looked at the colours of them? I am just thinking there could be an air leak on the inlet manifold or the inlet sside which would cause a lean mixture making the car difficult to start from cold (or hot)

 

[Cro_Tom]

Have you taken the sparkplugs out and looked at the colours of them? I am just thinking there could be an air leak on the inlet manifold or the inlet sside which would cause a lean mixture making the car difficult to start from cold (or hot)

Just before this problem starts, my car was on service - they changed the head seal, and then problems start's.

Which sensor gives a command to flap to open in cold start of engine?

Ok, before 2 weeks car was in other service - they clean out the inlet manifold, they reset all of parameters, and reset stepper motor position.

After then, when engine is cold, car works on 500-600 rpm - but don't turn off like before.
Before this, when car was working on cold, he was every time turn off...
Now is little better, he don't turn off, but works on low rpm.
And on cold start, without manual throttle, won't start.

 

[bluejohn125]

It seems you have probably checked everything that may be connected badly or damaged (i.e.electrical stuff).

Are you confident in the work that the garage did? If they set the cam timing wrong or something that can cause bad running and confuse the rest of the engine management. I think the difference in the car when it is cold or warm can be due to richer running when cold.

Try another compression test to see if the head is sealing and the timing is right.

 

[Cro_Tom]

Timing is good, they check it on last service.

Listen, when engine is cold, the flap in inlet manifold doesn't move when I start up the engine. It is closed, and the engine can't get air to start the engine.
In about 20 cold starts, only 1 or 2 times flap is opened and engine can start normaly.
So problem is in some sensor.

Which sensor detect temperature of engine?

 

[Cro_Tom]

hello again,

before 3 days, i take off a MAP sensor, and put it in the cold place where is temperature 5°C.

After several time, I was test the resistence of MAP sensor.

And it is very strange.

In 5°C, MAP sensor have a resistance that is parallel to temperatue in -10C.

In 25°C, resistance is parallel to 10C....

So i think I have found a problem.

Now I must find a other map sensor and test it, to be 100% sure that is map sensor wrong.