Technical Engine stalls with connected ECT sensor

[firebat]

Hello,

I am trying to figure what is wrong with old Tempra (1992). It has 1.8L DOHC engine (model 159A4.000). No CAT, no lambda probe (simple pot for emission control instead). The problem is the following: engine does not want to start easily, after it does, idles pretty fine, however once the throttle is touched, it stalls immediately. If I disconnect ECT sensor, problem disappears - engine reacts to throttle by picking rpm up without stalling.

I have checked ECT sensor by measuring resistance at different temperatures and it complies with specification. Throttle position, air intake temperature sensors are within specs too. Idle control valve is new and working. It is hard to be sure about MAP and CPS sensors as it is kinda hard to check them completely with simple multimeter, but what is possible to check is within specs. ECU contacts seems clean. Wires from sensors to ECU seem ok too.

Any ideas?

 

[dazzo666]

Hello,

I am trying to figure what is wrong with old Tempra (1992). It has 1.8L DOHC engine (model 159A4.000). No CAT, no lambda probe (simple pot for emission control instead). The problem is the following: engine does not want to start easily, after it does, idles pretty fine, however once the throttle is touched, it stalls immediately. If I disconnect ECT sensor, problem disappears - engine reacts to throttle by picking rpm up without stalling.

I have checked ECT sensor by measuring resistance at different temperatures and it complies with specification. Throttle position, air intake temperature sensors are within specs too. Idle control valve is new and working. It is hard to be sure about MAP and CPS sensors as it is kinda hard to check them completely with simple multimeter, but what is possible to check is within specs. ECU contacts seems clean. Wires from sensors to ECU seem ok too.

Any ideas?

GET A NEW ETC, SEEMS LOGICAL REALLY.....:slayer:

 

[s130]

ETC - please explain?

Have you checked that the air pypass on the trottle body is set correctly. The idle control valve is NOT designed to provide full idle control. If the base air bypass is too low and being compensated by the idle control valve then when you touch the throttle the ECU believes that the engine is now to be fed with air via the usual main air path. It accordingly tells the idle control valve to close and because the base air bypass is too low the engine could stall.

Below is the way to adjust / check the base air bypass.

VAE Idle Valve / Idle Setup
----------------------
With engine warm and running, remove connector to air bypass valve. Revs
should drop to about 750 rpm**. Reconnect connector and revs should rise to
1200 to 1300 rpm and then drop back to 850 rpm.

Sometimes the air bypass valve my temporarily stick. This can be overcome
by injecting/spraying WD40 or similar light oil into one or both sides/ports
of the valve assemley (remove a hoses)

The original Fiat setup information for a base idle of 750 rpm** with the valve
diconnected was changed via Service Bulletin. The correct setting of base
idle is to the same value that the ECU regulates via the VAE valve, ie 850
to 900 rpm, such that the connection and disconnection of the valve should
make little or NO difference in the idle speed. ie. No revs increase followed
by settling to controlled idle. Best idle also obtained with plug gaps of
1mm.

I used to always set mine to 900rpm and all my problems went away. The original 750rpm specified by Fiat cause many Tempras to have all sort of strange engine idle, overrun and partial throttle problems.

Hope this helps

 

[firebat]

ETC - please explain?

I think poster above mistyped. It is ECT (engine coolant temperature) sensor and not the ETC.

Base RPM (with idle control valve disconnected) are fine. I always set it to 850.

I think ECU enters service mode when it sees open ECT circuit, so it ignores other sensors and uses average values to keep engine running. That is why disconnecting ECT cures the problem of stalling. I suspect MAP sensor, but can't be sure. In anyway this car is going to be connected to diagnostics computer soon and hopefully it will give a clue what is wrong.

 

[s130]

oops, my mistake I meant ECT. Even so sometimes these acronyms get corrupted by the Italian to English translation which I why it is always best to qualify, like I did for the VAE (idle control).

So what does VAE stand for?

Valve Air Electronic/Electrical
Volume Air Electronic/Electrical
Vehicle Aspiration ?

 

[firebat]

Problem fixed. It was faulty MAP (manifold air pressure) sensor.