220TE rough running, sometimes

Alex Crow

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hfm uses an air mass meter to determine air flow into engine (the sensor on the intake pipe). pms uses manifold pressure and rpm mapping to calculate a value. your engine`s control unit needs this information to help calculate the correct injection period (how much fuel to inject at any given moment).

your regeneration valve is part of the fuel tank evaporative emission system, it allows fuel vapour vented from the tank to be safely and cleanly burnt off during the combustion process. the tank vent line has a pressure relief valve and charcoal cannister before the regeneration, or purge valve. disconnecting the down stream pipe and blocking off is not known to cause any problems for diagnostic purposes.

the correct test for the sensor involves use of diagnostic equipment and live data analysis, or swapping for a known good unit ;) disconnecting and running without will not really tell you much........

so the reason i mention air leaks, particularly new ones where you have been :lol: is this will severely affect the ecu`s ability to correcly meter fuelling, with symptoms most pronounced at low rpm and throttle opening. perhaps check again the oil breather pipe or air temp sensor mounting?
 
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DenisM

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Many Thanks

Many thanks for your detailed explantion - all makes sense - tomorrow I'll check for air leaks, could be I have not put something together correctly and is now leaking air.

I'll report back tomorrow night.

Thanks again


Denis
 

kth286

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Denis

In that picture you posted of the large air pipe going over the engine, I replaced the small rubber pipe in front of it (towards the camera) for a forum member recently as it had gone rock hard and there was a split where it joined the cylinder head cover.

It is that kinked pipe going from the butterfly air control to the cylinder head cover.

If yours needs replacing do get the end joining bit/s as well from the Merc dealer parts dept - very cheap.

As far as that regeneration valve on the NS inner wing is concerned (it has MOT on top of it) you can disconnect the pipe going from this valve towards the engine and block the end you have just pulled off.

Doing that will eliminate the regeneration valve from your investigations and you now might find the engine works well. Those valves can stick open, when they shuld be pulsing about once/twice per second when the engine is up to temp.
 

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hfm uses an air mass meter to determine air flow into engine (the sensor on the intake pipe). pms uses manifold pressure and rpm mapping to calculate a value. your engine`s control unit needs this information to help calculate the correct injection period (how much fuel to inject at any given moment).

your regeneration valve is part of the fuel tank evaporative emission system, it allows fuel vapour vented from the tank to be safely and cleanly burnt off during the combustion process. the tank vent line has a pressure relief valve and charcoal cannister before the regeneration, or purge valve. disconnecting the down stream pipe and blocking off is not known to cause any problems for diagnostic purposes.

the correct test for the sensor involves use of diagnostic equipment and live data analysis, or swapping for a known good unit ;) disconnecting and running without will not really tell you much........

so the reason i mention air leaks, particularly new ones where you have been :lol: is this will severely affect the ecu`s ability to correcly meter fuelling, with symptoms most pronounced at low rpm and throttle opening. perhaps check again the oil breather pipe or air temp sensor mounting?

Thank you for the above, and thank you for filling in some holes in this post,,its a problem that many have had, and some have never fixed the fault of rough idle on these cars.
 
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DenisM

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Air intake sensor knackered ?

Thanks for your help,

I checked this evening and an inclined to think that air isleaking arounf the small pipe you are refering to. I notice there are no clips athe ends to hold them in place, so will get some from MB.

There don't appear to be splits, but head end does not have a tight fit.

I also think the air intake temperature sensor is not working correctly (I removed it and then blocked hole and there was no difference to rough running.) Can this be cleaned or should I just replace ?

I think regen valve is sticking shut, because I cant blow through it.

Thanks again

Denis



Denis

In that picture you posted of the large air pipe going over the engine, I replaced the small rubber pipe in front of it (towards the camera) for a forum member recently as it had gone rock hard and there was a split where it joined the cylinder head cover.

It is that kinked pipe going from the butterfly air control to the cylinder head cover.

If yours needs replacing do get the end joining bit/s as well from the Merc dealer parts dept - very cheap.

As far as that regeneration valve on the NS inner wing is concerned (it has MOT on top of it) you can disconnect the pipe going from this valve towards the engine and block the end you have just pulled off.

Doing that will eliminate the regeneration valve from your investigations and you now might find the engine works well. Those valves can stick open, when they shuld be pulsing about once/twice per second when the engine is up to temp.
 

Alex Crow

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Thanks for your help,

I checked this evening and an inclined to think that air isleaking arounf the small pipe you are refering to. I notice there are no clips athe ends to hold them in place, so will get some from MB.

There don't appear to be splits, but head end does not have a tight fit.

I also think the air intake temperature sensor is not working correctly (I removed it and then blocked hole and there was no difference to rough running.) Can this be cleaned or should I just replace ?

I think regen valve is sticking shut, because I cant blow through it.

Thanks again

Denis

the regen valve is supposed to be shut until it is opened by ecu. that small breather pipe does not have or need any clips so don`t worry there. the intake air temp sensor will not noticeably affect running if unplugged so it`s probably ok - even if not working will still make very little difference.

is your problem now rough running, particularly at idle? there are many many possibilities including HT system and mechanicals so try to give us some more observations of symptoms with as much detail as possible, failing that get a techy involved!!
 
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DenisM

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Now fixed ?????

Hi All,

Thanks for all your advice; sorry for long delay in replying, been away without car and not done anything since last posting until today. That is apart from going to next village on a hot day, when there was no problem.

Got air intake temperature sensor fom MB in Swindon for the large cost of £14.04, fitted it and took car for run up road, so it is warmed up and likely to show problems. I had no coughing or spluttering and the car sounded wonderful, it purred along, better than I remember it ever sounding.

So please keep fingers crossed, that all now well.

In summary I have done following

1) changed plugs and leads which were looking corroded and in need of changing.

2) changed fuel filter, which i suspect had not been done for a while.

3) changed air intake temperature sensor which seems to have had greatest effect and caused greatest improvement.

I'll keep you posted.

Denis
 

kth286

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Air intake temp sensor is but a mere refinement to the settings. Not significant at all, so it will not be the real problem.

In my humble opinion expect more problems to come back.
 

Alex Crow

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could have been the ht, they do go gaga in this department.
 
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DenisM

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Ht ?

Thanks for suggestion - where do I find ht ? (Presumably there is a coil and lead somewhere ?)

Denis
 

jibcl500

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Sorry to hijack the thread but my 220 has recently started to run rough on tickover and when I select D or R the revs drop to 500 or so and sometimes it just stalls.

Ive checked everything thats been mentioned on here but last night I noticed the y pipe that sits underneath the inlet has a sizable crack in it so tonight I will remove the inlet support bracket and remove the pipes and replace if required.

jib
 

Alex Crow

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ht = high tension.

i was refering to your entire high voltage ignition system. ie 2x coils, 4x leads and caps and 4x spark plugs - all assuming you had cured the problem already like you said?
 
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DenisM

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Sorry I was not very clear

Sorry my question was not clear - where do I find the coils ?

Denis
 

kth286

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Sorry my question was not clear - where do I find the coils ?

Denis

Bolted to the inlet manifold.

On the later engine the two coils are under the top engine cover.
 

jibcl500

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Been working on my TE today and one thing I noticed on the HT lead, where the spark plug goes in the contact was black and mucky, with some sand paper rolled into a tube I managed to clean them so I could see shiny metal, I also wire wooled the top contact on the plug and the car seems to run a lot better know.

jib
 
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DenisM

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Rough again

Hi,

Someone previously said there was something else wrong, they were correct.

I have found insulation cracked on cable from air intake sensor to ECU cracked, hopefully you can see in picture below the cable I mean, circled in blue.

I have replaced as much as possible by soldering in a new cable from near the plug to behind the engine. However it is difficult to get right up to plug.

Mercedes can only supply the whole wiring loom, at a cost of £450. Anyone know anywhere that can supply either just the plug to which I can attach new cables, or plug and leads to solder onto existing cable ?

Happy New Year to all

Denis
 

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teabag

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Hi,

Someone previously said there was something else wrong, they were correct.

I have found insulation cracked on cable from air intake sensor to ECU cracked, hopefully you can see in picture below the cable I mean, circled in blue.

I have replaced as much as possible by soldering in a new cable from near the plug to behind the engine. However it is difficult to get right up to plug.

Mercedes can only supply the whole wiring loom, at a cost of £450. Anyone know anywhere that can supply either just the plug to which I can attach new cables, or plug and leads to solder onto existing cable ?

Happy New Year to all

Denis
Maybe jibcl500 still has the loom he mentioned in post #3 of this thread, if not I would try some of the breakers.
 

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