Oh that was a bad and a good idea at the same time!

[Rob]

Howzit all,

Well, last night I went to take my car to a friend's house. Now during the day I was on this forum, trying to find a fix for my problem. Which was a lot of hesitation on pull off. So I read somewhere (On this forum) that disconecting the MAF sensor will make the car run a bit better however will cause fuel consumption to go up and the car will read the fuel map since there is no input from this sensor. So I quickly pull the sensor out and go for a drive.

At firsted she seemed better. Then she seemed like she dropped to a lower gear, kicked a bit and spluttered. Going along I had my foot flat to the floor she stayed at constant speed then kicked again sped up and dropped gear again..she was all over the place, very inconsistant as well.

So I pull over at the garage and pop the hood reconnect the sensor and go on my way again. She now splutter while driving along...then she seems fine.

Now my hesitation is gone and she's now running perfect again. Wonder why she had the prob in the first place?

Ah well, alls well, ends well I suppose.

[genphreak]

Probably everything is reset as per the famous 'shogun reset'; due to being forced into Limpmode when the MAF is found to be 'missing'.

I'd expect that over time you will find (again) that something causes the ECU to make the wrong decision about combustion.

You probably need a new O2 sensor.

[Rob]

Why do you say that? Everything seems okay now. She doesn't smoke either.

On a side note: How would I know if a H;G has blown. She doesn't smoke and no oil in coolant and no white stuff on oil cap and dip stick. I mean would the car still drive fine or what?

[genphreak]

Why do you say that? Everything seems okay now. She doesn't smoke either.

On a side note: How would I know if a H;G has blown. She doesn't smoke and no oil in coolant and no white stuff on oil cap and dip stick. I mean would the car still drive fine or what?

If the ECU is at fault (as your little test suggests) it needs to get some incorrect information fed into the ECU for it to start 'causing' poor operation of the motor. The main source for this is the O2 sensor, which needs to be changed every 80-100k km anyway. Has it been?

As I said before, coolant in the exhaust fumes from a bad HG can destroy the O2 sensor instantly anyway, so be sure to test your HG properly before replacing the O2 sensor. Replacements are $50 USD and cheap to post. I posted a very cheap source I found online only recently.

Other sources are ignition, temp sensors (worth a check as per the Bently) and perhaps some other **** that is less likely that I am cann't think of).

Re the HG, why do u think it is blown? It could leak differently at different temperatures, but this condition won't go on for long- it will fail quite promptly after developing a small leak somewhere.

Do make absolutely sure your coolant is right and your cooling system working- read the Bently to know for sure. You can destroy an old HG fiddling around if you start heat-stressing the motor.

[Rob]

Well the HG was changed about 2 years ago after the cam belt snapped. I was just wondering as there is some stuff in the coolant. Doesn't look like oil though.

[Paul in NZ]

Rob you gotta work on one thing at a time...Have you cured the overheating???During your work on the cooling have you ever completely drained and flushed the cooling system completely?If so where is this stuff coming from?Or is this where you have seen this "stuff"

[Rob]

Have flushed the system many times. I think I've fixed the cooling. She hasn't overheated since. I see the 'stuff' in the expansion tank. I think it;s **** that is stuck at or in the rad tank no idea how to clean it?

[Ross]

Why do you say that? Everything seems okay now. She doesn't smoke either.

On a side note: How would I know if a H;G has blown. She doesn't smoke and no oil in coolant and no white stuff on oil cap and dip stick. I mean would the car still drive fine or what?

A faulty head gasket will either allow combustion gases into the cooling system thus pressurizing it--a lot,or allow coolant into the combustion chamber and/or oil ,or even manifest itself as an external leak.
If your not over pressurized look at your plugs, a really clean one can be from the steam cleaning effect the coolant in the combustion has.
If you're not seeing steam out the exh. or water in the oil are not using coolant and have no pressurization problems I don't see any reason to worry.

[genphreak]

Have flushed the system many times. I think I've fixed the cooling. She hasn't overheated since. I see the 'stuff' in the expansion tank. I think it;s **** that is stuck at or in the rad tank no idea how to clean it?

Easiest to pull the expansion tank and clean by hand, then resinstall and see if the stuff comes back. I'd follow the EXACT flush procedure in the bently before removing the expansion tank, maybe you don't want to bother removing the radiator as below as it the procedure might be good enough when doing it in the car: sure saves some effort if it is.

To pull the radiator and flush it you need a hose. Once removed from car put the hose in the top connection and force water the opposite way (ie back to the bottom hose) to normal flow (in lower & out upper hose). Position the radiator on the bottom hose tank when you do it so the upper tank fills and dribbles water down each filament under force of gravity and hose pressure until it dribbles out the bottom, otherwise you will only flush a few filaments.

ie Be sure to fill the radiator before standing it on the input tank and letting the water pour out the lower hose pipe.

Hose here V
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water out here

And find out if they changed the O2 sensor when the HG was changed. (normally this is needed as the HG kills the O2 sensor when it blows coolant into the cylinders.)

Be sure to use BMW coolant when refilling, you can use the previous stuff if it is less than a year old (btw; it is the same as volvo and saab blue coolant)

Nick