help please

[reedybopper]

Just fitted a new battery to my W202 (2.0 petrol, manual), however, the car now has very uneven tickover going up and down between 300-800rpm every second! The car will sometimes cut out and junctions etc.. so now resorting to driving with one foot on the brake and one on accelerator when approching junctions.

I have been reading various posts and people are sugesting cleaning out the butterfly valve and casing. Would this cure it? Could it be the new battery?

Any help would be great.

 

[gina2201]

I had a very similar/identical problem on my new car e220 coupe, and I cleaned the throttle body with some spray, very easy to do and worked wonders, car now idles fine, doesn't cut out on me at junctions or when braking. Worth a go at least? I have no technical knowledge as to the change of battery causing it but seems a coincidence. Good Luck in getting it sorted!

My last w202 used to idle high but sometimes would idle fine, was told idle control valve was missing a spring?

 

[television]

Just curious, does your car have an OVP relay 128 in the link


http://www.detali.ru/cat/oem_mb2.as...417717.418&CT=F&cat=44V&SID=54&SGR=045&SGN=03

 

[reedybopper]

Hi Television,

What is an OVP Relay? And if that was a link that you sent me, it does not appear to be working.

Many thanks.

 

[reedybopper]

Just an update, located what i believe to be the OVP relay, just behind the battery. Whilst the car was sort of running, I removed the 30amp fuse....the car spluttered then cut out. I replaced the fuse, and restarted the car, the removed the fuse again, and the car cut out again. I can only presume from this experiment that it may not be the OVP Relay or is it????

 

[television]

Just an update, located what i believe to be the OVP relay, just behind the battery. Whilst the car was sort of running, I removed the 30amp fuse....the car spluttered then cut out. I replaced the fuse, and restarted the car, the removed the fuse again, and the car cut out again. I can only presume from this experiment that it may not be the OVP Relay or is it????

Sorry about the link thats the first time that this site has been down but it will be back.


Yes you have found it.

Unplug the relay and insert a wire link between pin 30 and pin 87 and see how it runs

 

[reedybopper]

Further update which may help the cause. A friend told me that if I connect a jump lead to my live lead/terminal of my car, to the live terminal of another car, I would not lose my memory or my radio stations whilst changing the battery. I forgot to mention that I done whist swapping over the battery yesterday. however, I still lost my memory and to re-enter all the radio stations again.

Could this have caused a different fault, or would this re-direct you to a differnet fault?

 

[grober]

Did you also connect the negative connections of the 2 batteries involved?

 

[television]

As Grober there must have been a bad connection otherwise the code would have not been lost.

This is interesting and could have damaged the OVP relay this is why I said bridge it to see if it goes away

 

[reedybopper]

No!

 

[Howard]

Jumping Mercs ( or giving them a spike ) like you have done , can kill the OVP relay ...

I know , i've been through 3 of them ....

 

[reedybopper]

Jumping Mercs ( or giving them a spike ) like you have done , can kill the OVP relay ...

I know , i've been through 3 of them ....

How much are they from MB? or can I go to a breakers and just get one from any merc? are they all the same?

 

[television]

How much are they from MB? or can I go to a breakers and just get one from any merc? are they all the same?

Have you tried jumping between 30 and 87

 

[reedybopper]

Have you tried jumping between 30 and 87

No not yet, too dark outside, and I have just got in from work. Will hopefully try this tomorrow. If the car runs ok after trying the jump, i persume that I can conclude that OVP is shot. can I run whith the jump in place if it cures it?

 

[reedybopper]

Have just tried the wire link between 30 & 87 and yes, the car runs fine when this is done. I can only persume that I now need a new OVP Relay. Would this be correct? When I put the wire link across, I heard the fuel pump come on, and that was without the ignition on. is this normal? I would assume that it is not possible to drive with this wire link in place?

 

[grober]

Have just tried the wire link between 30 & 87 and yes, the car runs fine when this is done. I can only persume that I now need a new OVP Relay. Would this be correct? When I put the wire link across, I heard the fuel pump come on, and that was without the ignition on. is this normal? I would assume that it is not possible to drive with this wire link in place?

Its possible but not advisable since the OVP is there to protect sensitive electronic components from damage. Are you sure it was the OVP relay you bridged and not the fuel pump one? The OVP RELAY has a fuse mounted on the top under a clear plastic cover. Check that this fuse hasn't blown before replacing the relay itself.

 

[reedybopper]

Its possible but not advisable since the OVP is there to protect sensitive electronic components from damage. Are you sure it was the OVP relay you bridged and not the fuel pump one? The OVP RELAY has a fuse mounted on the top under a clear plastic cover. Check that this fuse hasn't blown before replacing the relay itself.

Now then, there's a thing! not sure now that you ask. The relay is in the boot, to the left of my battery, one big relay ( green in colour i think) with a 30amp fuse sticking out the top of it. And no the fuse has not blown.

 

[television]

As Grober this might be the fuel pump relay if there is no fuse on top,, to bridge 30 to 87 is the same to test the fuel pump relay

 

[reedybopper]

As Grober this might be the fuel pump relay if there is no fuse on top,, to bridge 30 to 87 is the same to test the fuel pump relay

Just been back out to the car and located the relay with clear plastic lid and a 10amp fuse on the top, put the wire bridge between 30 & 87. but I noticed no noticable difference other than my ABS warning lights came on, on the dashboard, however the car is now cold so the automatic choke will be enabled so tickover will be higher will it not? Also have replaced the 10amp fuse with a new one just in case.

 

[television]

Just been back out to the car and located the relay with clear plastic lid and a 10amp fuse on the top, put the wire bridge between 30 & 87. but I noticed no noticable difference other than my ABS warning lights came on, on the dashboard, however the car is now cold so the automatic choke will be enabled so tickover will be higher will it not? Also have replaced the 10amp fuse with a new one just in case.

The snag on the OVP relay is that there are a few pins parallel coupled to the 87 terminal.

Lets forget the OVP relay and go back to the fuel pump relay it would be best to take the top cover off and re solder every joint and make sure that they are all bright and shiny.

These relays are a known source of trouble