1996 1.4 VAG Idle Control Temp Sender
Discussion
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Irratic Idling and Engine Cutting Out on the Mk4/5 Polo.
After owning a Mk4 16V Polo for 7yrs I found there was a few problems with the design of the car but the most annoying fault was that the engine would cut out when I came to a stop, usually when I dipped the clutch.
Now this is a VERY common problem so if your car suffers from this then don’t worry you are not alone.
My girlfriend has the same model Polo and her car cuts out in the exact same manner. After many many visits to the dealership when the car was in warranty they couldn’t find out what was wrong with it, they said they tried everything but I very much doubt it or else the problem would be solved.
As I got fed up of the VW dealerships I took matters into my own hands, I mean how hard could it be to investigate?!
Also another problem which relates to this problem is irratic idling, sometimes the engine would ‘hunt’ for rev’s, it would rev on its own from 1000rpm to 1500rpm and then back down to 1000rpm and then to 1500rpm etc. This is extremely annoying when you are in traffic and people are looking at you thinking you got a dodgy right foot.
Here are the things you can do to try and solve the problem of cutting out and irratic idling. These are the things I did on mine whenever it started to play up which was pretty much every 2-3 mths depending on how much I used the car.
The first thing you can do is to clean the throttle body, this part of the engine controls the amount of air going into the engine and is operated by the throttle pedal. As the oil breather is connected to the airbox the crankcase gases are being put back into the intake system and the throttle body gets very dirty with oil.
So to clean the throttle body please following the following steps.
Before doing this, go buy some carb cleaner spray from Halfords or any car accessories shop.
Step 1.
Remove the VW badge from the airbox, this just pulls off.
Step 2.
Disconnect the air feed to the airbox.
Step 3.
Remove the allen key bolt from inside the airbox.
Step 4.
Remove the allen key bolt from the front of the airbox.
Step 5.
Unhook the earth strap from the airbox.
Step 6.
The airbox can now be removed from the engine, pull the air box away from the engine, it might need a good hard tug if its not been taken off before as it is held down by a rubber gromet.
Step 7.
Once the air box has been removed you can now see the throttle body, now disconnect the electrical connector, the main car battery does not need to be disconnected but it can be done if you feel safer disconnecting it.
Step 8.
Remove the 4 allen key bolts holding down the throttle body.
Step 9.
Take the throttle body off the engine, might need a tug if its not been taken off for a while as there is a rubber seal.
Step 10.
Take off the throttle cable, it unclips from the plastic.
Step 11.
Now use the carb cleaner to clean the throttle body. Spray the carb cleaner into the throttle body and use a cloth to wipe the oil away. Open the butterfly and clean the edges of the butterfly. Basically what I am trying to say is give it a good cleaning!!!!! Once clean leave the throttle body to dry off.
Step 12.
Now you need to clean the inlet manifold, spray the carb cleaner into the inlet and use a cloth to clean the inlet, clean as far in as your hands will allow, there is no problem in using quite a lot of carb cleaner to do this as it will burn off in the engine when the engine is started.
Step 13.
Once both parts are cleaned it is now ready to be put all back together, to refit just repeat the above steps in reverse kinda thing!
Step 14.
Once you are happy that everything has been put back together properly it is now time to start the car. You might need to give it some throttle to start as the engine will not like the carb cleaner when it is cranked over. Once the car starts give it a little bit of throttle to clear the carb cleaner out of the engine.
Step 15.
The throttle body cleaning process is now complete!
Read on if the engine is ‘hunting’ ,ie, reving by itself.
If the engine is reving by itself ,ie, the engine is wandering then stop the engine if the engine is running, disconnect the main car battery, you might need to note down the security code for the stereo. Leave the battery disconnected for at least 3hrs, the longer the better, this will reset the ECU and should solve the problem of the irractic ilding.
If the idling is still irratic after cleaning the throttle body and disconnecting the battery it is now time to change the temperature sender on the engine. The temperature sender monitors the coolant temperature and feeds the information back to the ECU. This part could fail therefore give false readings.
Both parts can be bought from any VW dealership.
Replacing this part will require the coolant to be drained or if you wanted you could remove the old temp sender with the coolant in the engine (make sure the engine and coolant is COLD if you are going to do it this way) and put the new sender in straight away, some coolant will come out so make sure you are prepared for a spillage of coolant.
To remove the temp sender take off the electrical connector. Pull out the plastic retaining clip which holds the temp sender in, carefully pull out the temp sender, once removed put the new sender in along with the o-ring and put the plastic retaining clip back and connect the electrical connector back. Give the sender a tug to ensure that it is secured properly. Refill the coolant to the correct level.
Restart the car and the idling should have settled down, if not then disconnect the battery again for a few hours to ensure that the ECU is resetted.
I have had many years of doing the above steps to my car and my girlfriends car with success. The cleaning of the throttle body is the main thing to do, I do used to do this on a regular basis to stop the engine from cutting out. It did stop it for a while and then it would return so once again the throttle was cleaned.
I hope this guide solves any problems you may have with your Polo Mk4/5.
Irratic Idling and Engine Cutting Out on the Mk4/5 Polo.
After owning a Mk4 16V Polo for 7yrs I found there was a few problems with the design of the car but the most annoying fault was that the engine would cut out when I came to a stop, usually when I dipped the clutch.
Now this is a VERY common problem so if your car suffers from this then don’t worry you are not alone.
My girlfriend has the same model Polo and her car cuts out in the exact same manner. After many many visits to the dealership when the car was in warranty they couldn’t find out what was wrong with it, they said they tried everything but I very much doubt it or else the problem would be solved.
As I got fed up of the VW dealerships I took matters into my own hands, I mean how hard could it be to investigate?!
Also another problem which relates to this problem is irratic idling, sometimes the engine would ‘hunt’ for rev’s, it would rev on its own from 1000rpm to 1500rpm and then back down to 1000rpm and then to 1500rpm etc. This is extremely annoying when you are in traffic and people are looking at you thinking you got a dodgy right foot.
Here are the things you can do to try and solve the problem of cutting out and irratic idling. These are the things I did on mine whenever it started to play up which was pretty much every 2-3 mths depending on how much I used the car.
The first thing you can do is to clean the throttle body, this part of the engine controls the amount of air going into the engine and is operated by the throttle pedal. As the oil breather is connected to the airbox the crankcase gases are being put back into the intake system and the throttle body gets very dirty with oil.
So to clean the throttle body please following the following steps.
Before doing this, go buy some carb cleaner spray from Halfords or any car accessories shop.
Step 1.
Remove the VW badge from the airbox, this just pulls off.
Step 2.
Disconnect the air feed to the airbox.
Step 3.
Remove the allen key bolt from inside the airbox.
Step 4.
Remove the allen key bolt from the front of the airbox.
Step 5.
Unhook the earth strap from the airbox.
Step 6.
The airbox can now be removed from the engine, pull the air box away from the engine, it might need a good hard tug if its not been taken off before as it is held down by a rubber gromet.
Step 7.
Once the air box has been removed you can now see the throttle body, now disconnect the electrical connector, the main car battery does not need to be disconnected but it can be done if you feel safer disconnecting it.
Step 8.
Remove the 4 allen key bolts holding down the throttle body.
Step 9.
Take the throttle body off the engine, might need a tug if its not been taken off for a while as there is a rubber seal.
Step 10.
Take off the throttle cable, it unclips from the plastic.
Step 11.
Now use the carb cleaner to clean the throttle body. Spray the carb cleaner into the throttle body and use a cloth to wipe the oil away. Open the butterfly and clean the edges of the butterfly. Basically what I am trying to say is give it a good cleaning!!!!! Once clean leave the throttle body to dry off.
Step 12.
Now you need to clean the inlet manifold, spray the carb cleaner into the inlet and use a cloth to clean the inlet, clean as far in as your hands will allow, there is no problem in using quite a lot of carb cleaner to do this as it will burn off in the engine when the engine is started.
Step 13.
Once both parts are cleaned it is now ready to be put all back together, to refit just repeat the above steps in reverse kinda thing!
Step 14.
Once you are happy that everything has been put back together properly it is now time to start the car. You might need to give it some throttle to start as the engine will not like the carb cleaner when it is cranked over. Once the car starts give it a little bit of throttle to clear the carb cleaner out of the engine.
Step 15.
The throttle body cleaning process is now complete!
Read on if the engine is ‘hunting’ ,ie, reving by itself.
If the engine is reving by itself ,ie, the engine is wandering then stop the engine if the engine is running, disconnect the main car battery, you might need to note down the security code for the stereo. Leave the battery disconnected for at least 3hrs, the longer the better, this will reset the ECU and should solve the problem of the irractic ilding.
If the idling is still irratic after cleaning the throttle body and disconnecting the battery it is now time to change the temperature sender on the engine. The temperature sender monitors the coolant temperature and feeds the information back to the ECU. This part could fail therefore give false readings.
Both parts can be bought from any VW dealership.
Replacing this part will require the coolant to be drained or if you wanted you could remove the old temp sender with the coolant in the engine (make sure the engine and coolant is COLD if you are going to do it this way) and put the new sender in straight away, some coolant will come out so make sure you are prepared for a spillage of coolant.
To remove the temp sender take off the electrical connector. Pull out the plastic retaining clip which holds the temp sender in, carefully pull out the temp sender, once removed put the new sender in along with the o-ring and put the plastic retaining clip back and connect the electrical connector back. Give the sender a tug to ensure that it is secured properly. Refill the coolant to the correct level.
Restart the car and the idling should have settled down, if not then disconnect the battery again for a few hours to ensure that the ECU is resetted.
I have had many years of doing the above steps to my car and my girlfriends car with success. The cleaning of the throttle body is the main thing to do, I do used to do this on a regular basis to stop the engine from cutting out. It did stop it for a while and then it would return so once again the throttle was cleaned.
I hope this guide solves any problems you may have with your Polo Mk4/5.
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