Very Rough Running / Stalling

[Andy_]

Hi All,

I'm looking for some help. I've had a heap of rough running issues, which have now become a lot worse after changing the battery. The car struggles to idle.

1. Disconnecting the MAF makes no difference, however putting electrical cleaner into the MAF does briefly allow it to run before cutting out again. The MAF is bosch, and was replaced by the last owner in the last 6 months.

2. The throttle feels disconnected from the car. The throttle body was stripped and cleaned, testing the peddle to throttle control the throttle body. The throttle body would only ever move a small amount. I would assume that the throttle should move fully open? It is buzzing, I left it for five minutes with the key in for a reset, along with the reset procedure and it makes no difference.

The car has recently had a full service with Air, Oil and Filters. The car has only 58k on it, so I am surprised at how badly it is running.

I will put some videos up shortly. Any help would be amazing.

Thanks,

Andy

 

[Andy_]

Some videos..

https://photos.app.goo.gl/z5vWiDZXrnrkUHSR7

https://photos.app.goo.gl/2zFAKdNTD1qWGb3Q6

 

[peterws1957]

Hi All,

I'm looking for some help. I've had a heap of rough running issues, which have now become a lot worse after changing the battery. The car struggles to idle.

1. Disconnecting the MAF makes no difference, however putting electrical cleaner into the MAF does briefly allow it to run before cutting out again. The MAF is bosch, and was replaced by the last owner in the last 6 months.

2. The throttle feels disconnected from the car. The throttle body was stripped and cleaned, testing the peddle to throttle control the throttle body. The throttle body would only ever move a small amount. I would assume that the throttle should move fully open? It is buzzing, I left it for five minutes with the key in for a reset, along with the reset procedure and it makes no difference.

The car has recently had a full service with Air, Oil and Filters. The car has only 58k on it, so I am surprised at how badly it is running.

I will put some videos up shortly. Any help would be amazing.

Thanks,

Andy

I would suspect the throttle body or the wiring to it. Have a look at vsandvs on You Tube. He has loads of videos on these throttle bodies and demonstrates the problems with them and how they should operate. Well worth spending some time on his site.

 

[Andy_]

I've stripped down the throttle body, the contacts on the potentiometers look fine and the gears and teeth look good. I wasn't able to test the motor properly, however spinning the motor I could see current which would suggest to me that the motor brushes are intact.

The car is now running worse then ever. I'm going to try a used accelerator position sensor and see if that cures it, as manually actuating the throttle now does nothing at all.

 

[LostKiwi]

You really need to get a code reader on it.

 

[mioba]

Did you spark the battery when replacing!

 

[Andy_]

You really need to get a code reader on it.

Yeah I've got an ODBII adapter on its way, failing that I'll need to get a mobile guy out with STAR to read the codes.

Did you spark the battery when replacing!

Apologies not sure what that means. I followed a normal battery replacement procedure, Negative first then positive to remove, then positive then negative to reconnect. Do you think something has fried?

 

[LostKiwi]

Yeah I've got an ODBII adapter on its way, failing that I'll need to get a mobile guy out with STAR to read the codes.



Apologies not sure what that means. I followed a normal battery replacement procedure, Negative first then positive to remove, then positive then negative to reconnect. Do you think something has fried?

You may not get anything out of it as your car may not support the necessary protocol.

The only readers I've found to read reasonably reliably are Carsoft and Star.

 

[Andy_]

You may not get anything out of it as your car may not support the necessary protocol.

The only readers I've found to read reasonably reliably are Carsoft and Star.

I thought this might be the case. I think i'll be phoning a mobile mercedes guy.

 

[LostKiwi]

If you were closer I'd pop down and help but 100 miles each way is a bit far...

 

[Andy_]

If you were closer I'd pop down and help but 100 miles each way is a bit far...

No worries! The cable has arrived. I'm preparing for no codes..

 

[Andy_]

And... no codes. I'll try and find someone mobile to come out.

 

[LostKiwi]

And... no codes. I'll try and find someone mobile to come out.

Did it manage to establish communication with the car or did it just show no codes?

 

[Andy_]

Did it manage to establish communication with the car or did it just show no codes?

Got a connection, no fault codes logged.

However I have progress! Turns out I didn't properly connect the throttle body connector back in. So i connected it, then left the ignition on for five minutes for the throttle to set up. Now the car fires up and idles normally which is great.

However, something is still amis. Using the throttle lever manually, I can build revs and rev the engine. Moving the action does not cleanly rev the engine though so there is definitely a problem with the TPS / Throttle body / throttle pot.

Additionally the accelerator pedal doesn't work well. Is there another sensor linked to the peddle?

Generally, I think I should do spark plugs and leads though and I'll potentially need to investigate the injectors.

 

[mioba]

Yeah I've got an ODBII adapter on its way, failing that I'll need to get a mobile guy out with STAR to read the codes.



Apologies not sure what that means. I followed a normal battery replacement procedure, Negative first then positive to remove, then positive then negative to reconnect. Do you think something has fried?

I remember moons ago with my w124 I sparked the battery changing it. Put it all back together and it ran rough as hell.

The son in law of my neighbour is a merc tech (been at merc forever), so I called him over. he had a look over and was fathomed until I said I sparked the battery. Ahhhaaa he said. He took out some fuse or relay (I can’t honestly remember and put it back). The car ran absolute fine afterwards.

 

[LostKiwi]

If you got a connection try looking at live data. You should be able to read the throttle position at the pedal and the butterfly position in the throttle body.

 

[Andy_]

If you got a connection try looking at live data. You should be able to read the throttle position at the pedal and the butterfly position in the throttle body.

Good idea! I've ordered a used TPS anywho. But I believe there is a failsafe in the pedal? I should be able to work out which is playing up.

 

[Andy_]

I don't flippin believe it. It won't run again. Local Mercedes guys are on a 3 week wait. I'll have to start replacing sensors and see where I get

 

[LostKiwi]

I don't flippin believe it. It won't run again. Local Mercedes guys are on a 3 week wait. I'll have to start replacing sensors and see where I get

Read the codes again....
And check the throttle as suggested above.

 

[badger_wazzala]

Good response above, check throttle position in relation to pedal sensor. Resistors/potentiometers give various readings dependant on where the pedal is so if these readings don't align with pre-determined points that the ecu is expecting then it'll definately affect idle/acceleration.

Whilst you're waiting for an OBD reader It's also very easy to remove spark plugs and check both condition and electrode gap. Also: either on a night when its dark or with your batman cape fitted and thrown over the engine, run an electricians screwdriver up and down the HT leads to see if they earth against it at any point. This would indicate failed leads of course.