97 mk3 golf Crappy idle and loss of power

[firelover123]

Hey all

I have a mk3 1.6l golf AEE engine

Last few days the idle has become really erratic and runs to a stall as approaching lights etc
also the power is pretty much not there any more, i get nothing from it and can barely go over 30mph, feels like a motocross bike does when you forget the take the choke off it justs bogs like hell and gives me nothing

got a diagnostic cable coming tomorrow hopefully, should have some basic vag software with it, i dunno if thats actually any good or how to get the full software/benefits of full software

any help on parts to check or using the software would be great.


Also on a side note theres a rubber pipe that runs from the underside of the airbox into a connection on the back left of the engine, about 15mm internal dia of the tube, but this was full of a greasy type gunk that had the colour of washed out mustard along with water, anyone any clue what that is?

Cheers!

[itavaltalainen]

try cleaning throttle body and then re-teach throttle to ecu with vcds (formerly known as vagcom).

the rubber tube you mention is the crankcase breather pipe. would recommend you remove and clean it, then refit

[SammoVWT]

To expand on what itavaltalainen said.

You can clean the throttle body quickly to make an improvement by using some carb/injector cleaner spray, and putting it on a cloth to clean inside the butterfly valve. If this makes an improvement then you will know you are on the right track.

In order to access the throttle body, you will need to remove the intake/airbox, which is usually supported by four bolts, once these are removed it should pull right off.

If you push the pulley where the throttle cable attaches you can see where the trouble is by looking down the throttle body. You may also need to do this with the engine running to use the carb cleaner if you are doing it the quick (but not a full clean) method.

The breather hose is attached to the airbox, and there should be a small plastic oil seperator. This may be gunked up with a mayo coloured substance which is consisting of water vapour/oil mixed together. This happens with short journeys/cold starts. Take the hose off and give it a clean with either some fluffy pipe cleaners, or take it off the back of the engine (some judicious twisting will help) and spray carb cleaner & use more fluffy pipe cleaners. Trust me a lot of rubbish will come out. Alternatively you can buy a new breather hose if yours is damaged or gunged up beyond repair.

To clean the throttle body properly disconnect the battery and then the plugs connected to the throttle body.

You will need to remove the four bolts of the throttle body (after the airbox/intake is removed). You will need a hex bolt extractor or an allen key. Make sure you bring a magnetic bolt fisher in-case you drop them in the engine bay somewhere. (typically down the holes of the intake manifold [black plastic tubing bolted onto the engine under the throttle body])

Be careful not to damage the clip of the throttle cable, take this off the bracket before moving the throttle body. Also, remove the vacuum hose (braided hose) from the top of the throttle body, this should leave a brass coloured pipe visible when removed.

Once these four bolts are out you should be able to lift the throttle body up. You may have a gasket, or you may not. If you do, replace it if damaged.

Now you can get to work cleaning the throttle body. You may need a cotton bud soaked in some carb cleaner to clean the brass pipe for the vacuum hose, be careful not to get any cotton stuck in it. You can also use cotton buds/cloth to clean the rest of the throttle body, making sure you clean the butterfly valve, and around the apeture of the plate. This if this is blocked when the plate is closed the car will not idle well.

Let the TB dry out, and fitting is in the reverse order.

Once done, you can use vag com (VCDS) to reset the throttle body, or adaption limit alignment which measures the resistance of the potentiometer in the throttle opening to max opening/closing of the throttle body, so when you use the pedal the ECU can scale load accordingly.

For Marelli ECU its group 098 from memory. Instructions are available on the web.

Additionally, you may need to tune up your ignition system. Do you know if the fault is occuring when the engine is cold/hot? Damp/Wet weather?

When was the ignition coil/sparkplug/ingition leads/dizzy last changed?

The more information the more accurate your diagnosis will be.

Many things can cause this engine to stall, from a breather pipe, vacuum line, fuel filter, O2 sensor, grounding faults.

The most important thing to do above all this is get a fault code scan.

If you get a scan done and you have no logged faults, you know most likely your sensors are ok. Which means you can move on to the basics of plugs, wires, fuel filters/leaks. I would strongly advise on it to avoid you spending money on a whim.

I have an AEE too by the way for some time now, so ive seen this issue crop up in a number of ways.