codes keep coming back after cleared with blink tester

[mr rosher]

first of all thanks to everyone who has helped me,
on the 8th of this month started the car after engine rebuild and / all well / no oil leaks/ no water leaks /and sounds great / good oil pressure on idle /and also very happy with myself as all the work was carried out on my own at weekends/
now over the last year since the head gasket went, iv`e had to replace,
air mass / o.v.p.r / complete rebuild of the wiring harnass from the E.C.U.to / the air mass, coils, temps sensors, and so on, / lamda sensor/ exhaust cam shaft/ throttle body/ now before the engine rebuild , no matter how many times i cleared the fault codes with the blink tester , sometimes it would be a day, sometimes three days and the codes would come back, same thing is still happening, when pluged in to pin 6 / 3 blinks which indicates ( intake air temperature sensor ) and on pin 8 / 4 blinks which indicate ( hot film mass air flow sensor ) now the only parts i did,nt replace was a small sensor that fits on the air inlet after the air mass and just above the manifold, and also some sort of sensor that fits in side the manifold under a plastic cover with two allen key bolts, can someone tell me if these could be the problem please
if it was,nt for the fact the car is hunting on idle when these codes appear i would leave well a loan, but as she is auto she keeps cutting out at cross roads and roundabouts, the car is a E280 1993 straight six, thanks for any advice

 

[Bolide]

Post a list of things you have already replaced and indicate if it was with new or s/hand parts. There's a finite list of things that can cause this kind of problem and it seems to be relatively common on this forum

Nick Froome
www.w124.co.uk

 

[kth286]

mr rosher

1. If your car is a UK model with the 16 pin rectangular shaped diagnostic connector then PIN 6 is SRS control module N2/2 diagnostics (air bags, seat belt pyro technic tensioners etc)
so your conclusion of 3 blinks being the intake air temperature sensor is wrong.

Where did you get that info.?????????????

3 blinks on that pin is the driver airbag squib.


2. Pin 8 is correct, it is the HFM sequential multiport fuel injection/ignition.

and you are correct that 4 blinks is the mass airflow sensor (MAF).

The sensor circuit has an implausibly high signal or it is open circuit.

You should check that the air filter is fitted properly with no gaps letting in unfiltered air which can contaminate the very sensitive element in the MAF. Are the electrical connections also secure when the engine vibrates on it's mounts pulling against the cable to the MAF and/or the MAF cable connections going to the multipin plug on the ECU.

3. The sensor in the air intake after the MAS is the air temparature sensor and if faulty would give 3 blips on the code reader, but on PIN 8 not PIN 6.

4. The sensor and flap in the intake manifold alters the effective length of the intake tract
depending on revs etc and provides optimum torque for any given speed and load condition.

Are you sure your overvoltage protection relay is reliable as that provides an input signal to the MAS at a critical level.

 

[mr rosher]

first of all thanks to everyone who has helped me,
on the 8th of this month started the car after engine rebuild and / all well / no oil leaks/ no water leaks /and sounds great / good oil pressure on idle /and also very happy with myself as all the work was carried out on my own at weekends/
now over the last year since the head gasket went, iv`e had to replace,
air mass / o.v.p.r / complete rebuild of the wiring harnass from the E.C.U.to / the air mass, coils, temps sensors, and so on, / lamda sensor/ exhaust cam shaft/ throttle body/ now before the engine rebuild , no matter how many times i cleared the fault codes with the blink tester , sometimes it would be a day, sometimes three days and the codes would come back, same thing is still happening, when pluged in to pin 6 / 3 blinks which indicates ( intake air temperature sensor ) and on pin 8 / 4 blinks which indicate ( hot film mass air flow sensor ) now the only parts i did,nt replace was a small sensor that fits on the air inlet after the air mass and just above the manifold, and also some sort of sensor that fits in side the manifold under a plastic cover with two allen key bolts, can someone tell me if these could be the problem please
if it was,nt for the fact the car is hunting on idle when these codes appear i would leave well a loan, but as she is auto she keeps cutting out at cross roads and roundabouts, the car is a E280 1993 straight six, thanks for any advice

hi bolide, you asked for a list of new and s/hand parts that i have replaced

new parts,

air mass sensor
o.v.p.r,
rebuilt wiring harness,
spark plugs,
lamda sensor,

s/hand parts,

throttle body,
cam shaft,

and then complete engine rebuild,

i hope this can be of some help, iv`e been working on her again today still the same codes, but clear the codes and start her she idles at 800rpm,
drop it in to d / or / r and the idle drops to 600rpm and feels as if its going cut out, go back into p / and she`s back at 800rpm any help, this is so frustrating, i hope you or someone can help with this.
and by the way kth 286 is right pin 6 is the SRS iv`e been looking at the wrong code sheet??

 

[mr rosher]

first of all thanks to everyone who has helped me,
on the 8th of this month started the car after engine rebuild and / all well / no oil leaks/ no water leaks /and sounds great / good oil pressure on idle /and also very happy with myself as all the work was carried out on my own at weekends/
now over the last year since the head gasket went, iv`e had to replace,
air mass / o.v.p.r / complete rebuild of the wiring harnass from the E.C.U.to / the air mass, coils, temps sensors, and so on, / lamda sensor/ exhaust cam shaft/ throttle body/ now before the engine rebuild , no matter how many times i cleared the fault codes with the blink tester , sometimes it would be a day, sometimes three days and the codes would come back, same thing is still happening, when pluged in to pin 6 / 3 blinks which indicates ( intake air temperature sensor ) and on pin 8 / 4 blinks which indicate ( hot film mass air flow sensor ) now the only parts i did,nt replace was a small sensor that fits on the air inlet after the air mass and just above the manifold, and also some sort of sensor that fits in side the manifold under a plastic cover with two allen key bolts, can someone tell me if these could be the problem please
if it was,nt for the fact the car is hunting on idle when these codes appear i would leave well a loan, but as she is auto she keeps cutting out at cross roads and roundabouts, the car is a E280 1993 straight six, thanks for any advice

hi kth 286, sorry mate iv`e been looking at the wrong code sheet??
your right pin 6 is the SRS,
the o.v.p.r was bought new in feb this year from my main mercedes dealer
and the car was only in use for a short time before i done the rebuild, but as you said there could be a fault with it, is there any way to check this/ or is there a way to check the correct voltage is getting to the air mass,
any help would be much appreciated as elecs is not one of my strong points thanks rod

 

[television]

As the car was fine before you did the rebuild, has something been disturbed.

I was looking at a similar post the other day where the guy had the same problems as you. his problems were solved by fitting new clamps to all of the pipes. I will try and find the post

 

[mr rosher]

As the car was fine before you did the rebuild, has something been disturbed.

I was looking at a similar post the other day where the guy had the same problems as you. his problems were solved by fitting new clamps to all of the pipes. I will try and find the post

hi malcolm, yes your right, i read the same post, the thing is my codes started before the rebuild but i never got chance to sort them out,
thanks for your reply,
malcolm i have read a few threads that say, if your battery is not putting out the right volts, then this can cause certain problems with running, could this be the problem im getting ??

 

[television]

hi malcolm, yes your right, i read the same post, the thing is my codes started before the rebuild but i never got chance to sort them out,
thanks for your reply,
malcolm i have read a few threads that say, if your battery is not putting out the right volts, then this can cause certain problems with running, could this be the problem im getting ??

Your post after all the work made me feel sad , all that work !!!!!!!

I am sure it is something silly. Its a fact that if the standing voltage on the battery is much under 12 volt, then starting blips, as they are called could bring up the codes, though turning off once started and starting again normally clears them, If the running voltage is around 13-14 volt it would not be this


Have you looked on benzworld or MBworld

I will see if I can find any special links

 

[kth286]

rod

Just a couple of thoughts.

1. There will not be many clues to problems until the engine has fully warmed up as the ECU uses fixed parameters and is not dependent on feedback from various sensors ie lambda probe etc etc. until engine is hot.

2. You know, I guess, that the car holds a low gear when driven until the engine is at a high temperature, so that the catalyst has a chance to be effective earlier.

3. It is normal for the idle speeds to be different in Park and Drive because of the drag of the toque converter etc in Drive or Reverse compared to park.

4. The intermittent cut out is the main problem for you -yes ?

5. Is the lambda probe feeding back the correct signals to ensure correct fuelling at low revs ?????????

6 Are you sure the coolant temperature sensor is effctive as this is also a critical component in the feedback loop for correct fuelling. ???

7. The charcoal canister system should only be feeding back the vapours after the engine has warmed up so avoiding sluggish/rough idle. Is the temperature switchover valve operating OK to allow this only after warm up. ???

 

[mr rosher]

hi david thanks for replying, and now i think about it, i had an old volvo that use to do the opposite to this, when cold would run like a bag of sh.. , but once warmed up would be fine, the car does this once she warms up, on start up the revs are a bit higher as they should be i think ?? and all well, but when she`s been running on idle for say 5 minutes the revs drop to 800 rpm and thats when the problems start , the lambda sensor was replaced in feb this year, but how can i check if its sending back the correct signals,
the coolant temperature sensor has got me thinking, ??? which one is this??? as i remember i have 3 plugs to connect to the water pump, and would this cause me to get the code readings on pin 8 as air mass problems. once again thanks, rod