Track day killed my car! - The Unofficial BMW M5 Messageboard (m5board.com)

QSZ · 16th April 2005, 04:04

I am wondering if anybody has had this problem and can be of help.
I was at a track day last Sunday and my 3.6 just started to run extremely rough to the point I couldn't make it back to the pits area. Towing the M5 to the pits was not a good look

It is over fuelling and running the injectors to full duty cycle. Have checked all sensors/MAF and it looks like the ECU has some issue. Can anybody shed some light on this for me?
Thanks,

Simon

Brian M5 · 16th April 2005, 10:40

Sorry to hear about your problem and I can't shed any light on it either.

It does raise an issue over track days in the car though. I have done one and it took a week to get the smile off my face.
It has to be said though, that with repairs costing an arm and a leg (my latest being a small leak on a self levelling valve costing £400 to sort out), there may be more economical ways of getting your track day fun. I admit that the reason for me not doing more track time is the mechanical worry of taking a 10 year old car and thrashing it at a time when it is approaching senility.
Or, I'd love to hear that there is no problem with rev limiting through the gears for a few hours per month and only need to concern myself with tyre replacement and keeping it away from the scenery.

A spare engine and gearbox would be a luxury and if Insurance companies were not so **** obstinate I would have had a full suite to pick from.

Hope the board can help out.

farrell · 16th April 2005, 11:30

Quote:

Originally Posted by QSZ

I am wondering if anybody has had this problem and can be of help.
I was at a track day last Sunday and my 3.6 just started to run extremely rough to the point I couldn't make it back to the pits area. Towing the M5 to the pits was not a good look

It is over fuelling and running the injectors to full duty cycle. Have checked all sensors/MAF and it looks like the ECU has some issue. Can anybody shed some light on this for me?
Thanks,

Simon

Hi there QSZ
Dont start panicking yet. Its easy to think the worst with these old girls & Brian has raised some fair points.
Are the spark plugs & leads ok ? (Just checking) A track day can punish the plugs.

I would get the DME fault codes read as a starting point.
I would then guess that the fault will not lie with the engine management but with either the engine side water temp sender giving a false reading to the DME & putting the car into cold start strategy. This can be the sensor or the cooked wiring that becomes embrittled due to 10 yrs of Upheat.
Next up is the Oxygen sensor gone down which is far from unusual. Either way the fuelling will be shot with either option. Brittle wiring & cooked connectors has been a issue with my car in the last yr or so.

Things to fix start becoming more expensive after these two checks but assuming the DME is ok, this should point you in the right direction.

These cars can survive a track day, even the most punishing circuits like Nurburgring or Bathhurst as a comparison for the Southern Hemisphere can be fine as long as do a couple of laps & let the car cool down before going again.
There are far better choices for track cars & 1.7 odd metric tonnes does take its toll on the underpinings. Only a personal view mind you so not worth more than that.

Regards
Farrell

cardriverm5 · 16th April 2005, 12:33

Simon.

I think I can help,had the same thing on my 3.6......
Had the fault codes read...no problems at all????
New air flow mass meter didn't cure it (still overfueling)
My mechanic is an Ex bmw tech and has spent alot of time trying to find the problem in his spare time and has come to the conclusion that the management system is not stock on my car and the chip (Eprom) has a fault, he's tested everthing else

so....
today he gets the new chip and fits it after removing the alien bits and hopefully it should be back to business, I will let you know later.
I think you may have the same problem so I would go have the DME checked out first, (find a good company who remap chips to do this)
Oh and by the way the engine will run if the O2 sensor was disconnected totally (it wouldn't overfuel like it is doing)
Hope this helps, Andy S

QSZ · 16th April 2005, 14:51

Hi Guys,

thank you all for your quick replies.

Brian, I have had it out on a track day before (Philip Is. Grand Prix Circut) and it was sensational, rounding up much more modern cars with ease. It did not have as much as a single problem, even brakes worked great with turbine trims on. Oil temp has to be checked in hot weather. My car is like new with only 140,000klms on it. You just have to remember your limits and all will be OK, you are not in a championship so remembering this you should be able to keep it off the walls.

Farrell, yes checked leads and spark all fine. DME is clear of faults. (DME can't tell you if it is faulty though). Checked all water temp sensors. O2 sensor won't cause the car to go to max. injector cycle so we don't think it is this. No fault code so it hasn’t failed and still is with in factory spec according to service OBD computer. Wasn't going to take it on this day but my Audi V8q track car met with an unfortunate workshop accident :-0

Andy, I am in the business of tuning cars so have already replaced the stock data chip with a new one, no different unfortunately. Data had no faults or corruption but changed it anyway just to be sure. (still haven’t chipped it, too busy with other peoples cars) Their maybe a fault in one of the processors or resistors in the DME. I will try unplugging the o2 sen. just to see what happens.

Thanks again Guys.

Simon
QSZ

E34M5 Scott · 16th April 2005, 17:28

I would echo farrell on the brittle wiring part. I had an A2 Jetta GLI that would regularly display the symptons you are describing. All the diagnostics pointed to the ECU. Each time it was a ground wire that had become brittle and broken. Hope this helps.

farrell · 16th April 2005, 19:28

Yes the the car will run with the with a disconnected Lambda sensor but it will not fuel correctly. The system is a closed loop 3 way control using Lambda to define the A/F ratio. When you disconnect the Lambda probe the system goes open loop with consequent variances to fueling as the ECU tries to compensate for mixture variances which will always increase HC levels whilst it attempts to pull the catalyst op temp up above 250 degrees C (400 to 800 C is optimum )

On other cars with close coupled Catalysts, this over fuelling would usually destroy the washcoat treatment on the monolith. Lucky for us that the cats are under floor..

It is entirely possible with an intermittant operation of the Lambda probe to get over fuelling but if you also have incorrect cold water temp readings when the cooling system is already at optimum working temps returned to the DME, this will also incur a cold start duty cycle as fuel will be increased to support a cold start the DME believes is required.

This is all moot however if the fuel injectors are running @ full duty with no return to dwell.

I wonder QSZ s CAR is fitted with cruise control..!

Its very hard for any of us to get a feel for the fault when diagnosing thousands of miles away.

I hope QSZ resolves his issues regardless

Regards Farrell

QSZ · 17th April 2005, 03:09

I will check all the ECU earths and keep plugging away with it. When it happend the car was going strong. Just had a little dip in power when acc., then brake for corner and then went to power out and nothing but coughing and spluttering.

I don't have a cruse cont.

Cheers

Simon

cardriverm5 · 17th April 2005, 15:20

Simon.

New chip fitted......No change

Complete new E.C.U. to be fitted on tuesday, if that don't work the guy from the e.c.u. company is coming to the car..

Keep you posted

Andy S

QSZ · 17th April 2005, 15:46

Hi Andy,

I will keep at it here as well. I was supposed to get a loaner ECU from somebody today, but he didn't call.

Lets hope one of us can sort this quickly and help the other. I am missing my rough idle and M acceleration. The AmD cooper S just doesn’t cut it even though it has 210bhp.

Have a good Sunday,

Simon