BAS/ESP malfunction light on permanently

[mbohner]

My 99 ml320 BAS/ESP malfunction light is on permanently. It says in the user manual that " it is possible that now only partial engine output will be available".
I would like to understand why this happens and whether it could be a source of the misfiring I have on 3 pots. The engine warning light flashes on when this happens. New coils, leads and plugs have not solved the misfiring problem.

 

[television]

My 99 ml320 BAS/ESP malfunction light is on permanently. It says in the user manual that " it is possible that now only partial engine output will be available".
I would like to understand why this happens and whether it could be a source of the misfiring I have on 3 pots. The engine warning light flashes on when this happens. New coils, leads and plugs have not solved the misfiring problem.

Your BAS ESP fault will be caused by a faulty brake light switch, £9 and easy to fit, though this fault kill the speed signal in the SAM,ti should not make the engine miss fire.

Malcolm

 

[mbohner]

Thx

Thx for you input. I'm perplexed what could cause the misfiring on these three cylinders when the main electrical components have been changed. If the problem was across all of the cylinders I'd start looking at air flow/mixture issues, etc .

 

[television]

I will see what I can find.

Malcolm

 

[eric242340]

Thx for you input. I'm perplexed what could cause the misfiring on these three cylinders when the main electrical components have been changed. If the problem was across all of the cylinders I'd start looking at air flow/mixture issues, etc .

Your BAS/ESP light and the missfire and not connected. But in the case of the missfire, try different spark plugs first. Interestingly you seem to know which cylinders are missfiring, how do you know this?

 

[stats007]

Playing devil's advocate the misfire theoretically could be related to the ESP fault. This ECU monitors wheel speed and longitudinal and lateral acceleration amongst other things and will automatically brake and reduce engine output by cutting fuel delivery if appropriate.

 

[eric242340]

Playing devil's advocate the misfire theoretically could be related to the ESP fault. This ECU monitors wheel speed and longitudinal and lateral acceleration amongst other things and will automatically brake and reduce engine output by cutting fuel delivery if appropriate.

Hi stats007, or should I say Devils Advocate. The Electronic Stability Programme is just what it says and has absolutely nothing to do with missfires. The ESP/BAS system is not related to this type of engine management problem

 

[television]

Most things that are switchable by the consumer are not really part of the engine management, though the Brake light switch kills the speed signal in the LH front SAM.


Malcolm

 

[eric242340]

Most things that are switchable by the consumer are not really part of the engine management, though the Brake light switch kills the speed signal in the LH front SAM.


Malcolm

Malcolm this is true, but it still has nothing to do with a missfire.

 

[stats007]

Hi stats007, or should I say Devils Advocate. The Electronic Stability Programme is just what it says and has absolutely nothing to do with missfires. The ESP/BAS system is not related to this type of engine management problem

I'm afraid you're wrong on this - the ESP system is combined with ASR and uses the electronic engine management to act as an e-diff.

 

[mbohner]

Thx for all suggestions. A little history. The BAS/ESP warning light came on first and it was only a week or two later that the engine problems started. The most noticeable aspect was a dramatic loss of power. Upon examination a hand held tester attached to the socket under the dash showed misfiring on pots 2, 3 and 5. 3 coils, 12 plugs and 12 ignition wires were then changed. After the changes the car was still misfiring. The tester, attached to the car whilst it was being driven showed misfiring on pot 5 first and then pot 3 and pot 2. The loss of power is again very noticeable. The car appears to rev perfectly at a standstill but under load/motion starts to miss.

The ABS/ESP remains on.

 

[stats007]

I'm in agreement I don't think the two are linked but the possibility does exist. Have you run the car very low on fuel recently? Sounds like possible contamination in the injectors.

 

[eric242340]

I'm afraid you're wrong on this - the ESP system is combined with ASR and uses the electronic engine management to act as an e-diff.

This too is true, but it has nothing to do with a missfire. so whats the next thought?

 

[mbohner]

Thx for the posts. Another person, not in the forum, also suggested that it might be a fuel management problem--the key being it happens on same pots again and again. The suggestion that the injectors are contaminated or blocked is something I'm working on. My first step was to buy a bottle of fuel injector cleaner and put it in the tank. Its recommended that you do this when the tank is near empty. However, my tank is half full. Other than that I don't know what to try next. How do you test for or fix injector problems?

 

[television]

Thx for the posts. Another person, not in the forum, also suggested that it might be a fuel management problem--the key being it happens on same pots again and again. The suggestion that the injectors are contaminated or blocked is something I'm working on. My first step was to buy a bottle of fuel injector cleaner and put it in the tank. Its recommended that you do this when the tank is near empty. However, my tank is half full. Other than that I don't know what to try next. How do you test for or fix injector problems?

I think that before you go any further, you should get a fault code read out.

Get it done by an idie, engine fault codes are easy to read. If you go blindly on you could upset things that were working.

Thats what I would do.

Malcolm

 

[stats007]

Do MB recommend injector cleaner? You can have them cleaned ultrasonically I believe? No experience of this myself however. Fuel filter may be worth looking at before you go this route as it may well continue to contaminate if that is the issue.

Malcolm I don't think any specific fault codes are showing from what the chap has said - just that there is a misfire on specific cylinders.

 

[diagnostics]

In my experience with these with 3 cylinder misfire it has always been MAF sensor fault which shuts 3 cylinders down and causes the plugs to get fueled up and wont clear, check on diagnostic tool, seems maf reading only has to be slightly low to cause this fault, also another i recall was water sitting in the u bend of the fuel lines at the back of the cylinder head but more likely the MAF, esp is seperate fault, hope this helps

 

[mbohner]

As suggested my next step is to get a fault code read out. I believe that certain fault codes suggest a MAF sensor fault but don't necessarily confirm that is the case.

My testing of the car today has revealed an unusual feature of the problem. If the car is put under heavy load, in second or third gear typically, the car loses power and starts to miss so badly that the whole car shakes ( 3 pots out?) The car will continue to run like this even as the revs drop off. Idling at a standstill the engine is still misfiring. However, after switching engine off and restarting, the engine is smooth and there is no sign of a miss even at high revs. This process can be repeated again and again.

 

[mbohner]

Thx for everyones input to date.

The local garage just reported current error codes of PO170 and PO173 and misfiring codes in memory. They also recommended replacing the MAF.

I'm going to install a new MAF but I first will make another attempt to clean the existing MAF.

 

[diagnostics]

Cleaning wont work at all, waste of time, get garage to check maf on oscilloscope and check for any faults in sinewave