My car engine tends to stall when the engine is cold.

Question

Hi guys,

I have got Golf IV 1.6 (benzine) and after I start the cold engine I have problems to keep the spins up. It tends to wind down until it stalls. This phenomenon is only with the cold engine, or else, when I start the car after a longer time. During a ride there are no negative effects.

Last time the problem was displayed by car jerking (during the beginning of the ride) as if into the engine didn't go any petrol. After one minute evrything was OK.

Thank you a lot

Answer 1

Yes, this is a cold-start/run problem.  The air/fuel mixture is running too lean for you when the engine is cold.  The vehicle's onboard computer is supposed to adjust the mixture based on temperature as well as load and acceleration.  For some reason the computer is adjusting wrong.  Let's look at the possibilities why this might be:

- The computer could be receiving erroneous information from one or a couple of its various sensors.  Assuming that the car runs fine when the car warms up I would most probably rule out the Manifold Air Pressure (MAP) or Mass Air Flow (MAF) sensor; whichever one of those your car has. There is a Coolant Temperature Sensor (CTS) which is supposed to tell the computer if the engine is cold and when it warms up. It could be that the information is not getting to the computer (the sensor could be defective or the wiring from the sensor could be disconnected or broken). I am not sure about VWs but I would assume the car would illuminate a Check Engine Light (CEL) if these were the cases.

-  Certain devices on the engine are supposed to be inactive when the engine is cold. One such device is the Exhaust Gas Recirculation (EGR) valve. If it is stuck open it could be introducing unwanted exhaust gases into the intake at the wrong time.

-  Components on the engine are supposed to be tightly sealed so as to prevent vacuum leaks. In some instances a cold engine will have minute gaps in these areas; but when the engine is warm and the metal expands the gaps close up. This is probably pretty unlikely but worth a check.

- Highly unlikely, but possible: The Oxygen (O2) sensor is what tells the computer if the mixture is too rich or lean for the condition that the engine is running in. It only works when it is properly heated by a heating element wired into the system. Usually the engine will run and the computer is supposed to compensate ( if the O2 is not warmed up yet) by running without the O2 information until the O2 is heated, but on today's sensitive cars the transition could possibly be real noticeable. You should get a CEL illuminated for this one, too.

Your best bet is to have someone plug a diagnostic scanner in the diagnostic link of the vehicle. This will alert the technician to the proper code to find the most probable cause in order for them to effect the proper repair.

Answer 2

Your water temp sensor is bad.

When the engine is cold it needs more fuel.  The computer senses the engine temp (coolant temp) and runs the car in choke mode (rich).  The water temp sensor is the major sensor (not the MAF sensor) that make the car run rich when the engine is cold.

The MAF sensor just sense how much air is being sucked in, not how much air / fuel the engine needs.

It is also the reason why many cars use too much fuel (if the engine thinks the engine is always cold and run rich).

Good luck...

P.S.  the post above is wrong about MAF.

Answer 3

cold engine starting problem

a cold engine needs a little more gas at first to keep it going.

Your car should have a MAP sensor on it. its on or in front of the throttle body. Sometimes the sensor's sensing wire gets dirty and sends the incorrect signal. You can get a spray can of MAP cleaner and clean that sensor. This will most probably be it.