The MP9 Saga continues
I blogged previously about the software bugs in the 1.4 MP9 fuel injection computer as fitted to the Citigolf (an upgraded mk1 still built and sold in South Africa) 1.4i and the Polo 1.4i. As it goes with these things, since the engine was running fine, it was moved to a back burner.
But recently a couple of weird things started to happen: Sometimes when you start it it would idle quite high (settling down a minute or so later), or it would idle unevenly. These were all signs that the problem is getting worse, so I finally started to do something about it.
First I discussed the problem some more with the auto diagnostic makers in our building. There is another additional issue that owners of these vehicles need to be aware of. This issue is in the throttle body itself. On the side of the throttle body (closest to the firewall) you will find an enclosure that houses the TPS (throttle position sensor) and a Servo motor. This Servo motor's job is to control idle speed. Over time, the gears in the servo motor becomes worn. This makes it very hard for the fuel injection computer to properly control the idle speed and causes the engine to hunt, that is, engine speed fluctuates up and down.
The first step in my repair process was to clean out the throttle body. The MP9 keeps track of the resting position of the throttle, and before you can reset the fuel injection computer you first need to clean out any dirt that might cause the angle (as measured by the TPS) to be higher than the factory default. If you don't, the fuel injection computer will just store this value the next time you turn the car off and the "fix" won't last.
So I drove down to the local Midas and bought a can of carburetor cleaner (as recommended by the Toyota Workshop manual, I figured if it is good for a Toyota, it should be fine for a VW). A couple of minutes later the throttle body was clean as a whistle. The plan is to have the computer reprogrammed to factory defaults on Monday.
In the meantime the car is behaving a little crazy. It idles at 1500 rpm. It hunts a little, but not too bad. It absolutely refuses to be driven slowly (that is, at engine speeds of 1500 to 2000 RPM) for more than a couple of seconds. It seems the throttle body is fine though, as the (somewhat confused) fuel injection computer has no trouble regulating the much higher idle speed.
Word of warning for other DIYers, be very careful if the car has a catalytic converter. Carburetor cleaner is flammable and could damage your CAT. Luckily for us, very few cars have CATs in this country. This will change in 2008 though, when legislation will force all new vehicles to have a CAT. After that, motoring will NEVER be cheap again: replacing a CAT is VERY costly.
Watch this space for details :-)
But recently a couple of weird things started to happen: Sometimes when you start it it would idle quite high (settling down a minute or so later), or it would idle unevenly. These were all signs that the problem is getting worse, so I finally started to do something about it.
First I discussed the problem some more with the auto diagnostic makers in our building. There is another additional issue that owners of these vehicles need to be aware of. This issue is in the throttle body itself. On the side of the throttle body (closest to the firewall) you will find an enclosure that houses the TPS (throttle position sensor) and a Servo motor. This Servo motor's job is to control idle speed. Over time, the gears in the servo motor becomes worn. This makes it very hard for the fuel injection computer to properly control the idle speed and causes the engine to hunt, that is, engine speed fluctuates up and down.
The first step in my repair process was to clean out the throttle body. The MP9 keeps track of the resting position of the throttle, and before you can reset the fuel injection computer you first need to clean out any dirt that might cause the angle (as measured by the TPS) to be higher than the factory default. If you don't, the fuel injection computer will just store this value the next time you turn the car off and the "fix" won't last.
So I drove down to the local Midas and bought a can of carburetor cleaner (as recommended by the Toyota Workshop manual, I figured if it is good for a Toyota, it should be fine for a VW). A couple of minutes later the throttle body was clean as a whistle. The plan is to have the computer reprogrammed to factory defaults on Monday.
In the meantime the car is behaving a little crazy. It idles at 1500 rpm. It hunts a little, but not too bad. It absolutely refuses to be driven slowly (that is, at engine speeds of 1500 to 2000 RPM) for more than a couple of seconds. It seems the throttle body is fine though, as the (somewhat confused) fuel injection computer has no trouble regulating the much higher idle speed.
Word of warning for other DIYers, be very careful if the car has a catalytic converter. Carburetor cleaner is flammable and could damage your CAT. Luckily for us, very few cars have CATs in this country. This will change in 2008 though, when legislation will force all new vehicles to have a CAT. After that, motoring will NEVER be cheap again: replacing a CAT is VERY costly.
Watch this space for details :-)
posted by ispburger at 10:28 am
4 Comments:
never use carb cleaner on an mp9 intake. they are very aggressive on the maf sensor rather use electrical cleaner or brake cleaner.
How would one know how to adjust the rhrottle butterfly on mp9.it seems like its going past the limit it shouls and thwn i gain loaa of power.what is thw right aetging for butterfly when open
Im losing allot of power on my 8valve.at 4000 rpm it seems and feels like im hitting the rev limetor ans then it starts to miss and then idle high and low.why would this happen?any suggestions please
Next, you can try to determine whether you should take your car to a mechanic to get it checked. DIY code readers are great for quick diagnosis, but are only good for general issues. If you are curious to know more about diagnose car fault, read me.
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