Recently acquired my '93 280 E which I believe is a lot of car for the money they change hands at these days. I noticed a misfire from day one that only became apparent when I brake after driving a short distance. If I sit in traffic with it in Drive the shaking gets so violent I have to tap the accelerator to 'ride it out'. There is a suspected weeping head gasket but there are no signs of oil/water mix or pressure build up in the water hoses. I need to drive it up to Birmingham this weekend ( 2 1/2 hrs ) where I can get it looked at in a couple of days. If I start the car and leave it running it doesn't misbehave, if I drive it and apply the brake.... the juddering and surging starts ?????
W124 280 E Misfire
- Thread starter DelBenz
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Just thoughts and nothing else.
You say that the juddering starts when you brake, the brake is coupled to the Vacuum system,air leaks upset the idle and this is also coupled to the vacuum system.
Just thoughts
You say that the juddering starts when you brake, the brake is coupled to the Vacuum system,air leaks upset the idle and this is also coupled to the vacuum system.
Just thoughts
I've come across this problem before.Turned out to be the engine loom.With the engine running in neutral,hold the loom in the area where it crosses from the baulkhead to the inlet manifold & gently manipulate it.This will cause it to miss if it is failing in this area.
I would be wary of driving it any more than you have to,certainly not for a couple of hours,as if there is a loom fault,the last thing that you want to do is fry the ECU as well!
I would be wary of driving it any more than you have to,certainly not for a couple of hours,as if there is a loom fault,the last thing that you want to do is fry the ECU as well!
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I can tell that the the loom that runs across the top of the engine has been worked on in the past as its wrapped in self amalgamating tape. Been driving the car for over a week now with the problem. I am going to disconnect the brake servo to throttle body hose shortly to check for leaks and proper valve operation. Other symptoms I am noticing is a strange clanking sound which comes on goes form underneath the car towards the gearbox end - like something knocking on an exhaust box. There is also a that smell like somthings over heated after a run. I had the engine steam cleaned and silconed and thought it might be that burning off first.
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Steam cleaning gets moisture into part that would never get moisture in in any normal way.
Meanies post is very relevant here in view of the above
Meanies post is very relevant here in view of the above
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The problem was apparent before the steam clean. I'm going to check out the vacuum first as it seems a like a logical starting point. Being a new (recent) car I can't vouch for any of the electrics or breathing until I've gone through the breaking in period.
It's also easy enough to open up the loom with a modelling knife.
The surging comes about because the electronics try to compensate for the drop in revs,causing a torque reaction which then brings the wiring back together.The loom is easily removed & very simple (if a little time consuming) to repair on the bench.
Don't rule out the coil packs either.To check,have somebody hold it in gear (put the rear wheels in the air) & CAREFULLY remove the signal wire from each of the packs in turn until you find which cylinders are dropping.Then swap the coil with another & if the missfire moves then you'll know that it's the coil.If it remains where it was then you have a control fault (wiring?).
The surging comes about because the electronics try to compensate for the drop in revs,causing a torque reaction which then brings the wiring back together.The loom is easily removed & very simple (if a little time consuming) to repair on the bench.
Don't rule out the coil packs either.To check,have somebody hold it in gear (put the rear wheels in the air) & CAREFULLY remove the signal wire from each of the packs in turn until you find which cylinders are dropping.Then swap the coil with another & if the missfire moves then you'll know that it's the coil.If it remains where it was then you have a control fault (wiring?).
Ian B Walker
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I have come across this before. I turned out to be a coil pack breaking up under load.
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Coil pack are known to do this as Ian and meanie says, do not disturb the wiring more that you have to when swapping them over
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Uh Oh ...
Well it wasn't a vacuum leak - spraying flammable stuff all around the hoses didn't 'excite' the engine.
It wasn't the loom, as noted previously it appears to have been rewired.
But ! one of the plugs had this brown stuff on it and appeared to be smoking steam - leaky headgasket getting water onto the plug, but not leaking so as to mix the oil with water. A blast up and down the M40 seemed to have improved matters but I will have to have it done at some stage. £250 - 300 labour :? I'm sure it will be money well spent.
Well it wasn't a vacuum leak - spraying flammable stuff all around the hoses didn't 'excite' the engine.
It wasn't the loom, as noted previously it appears to have been rewired.
But ! one of the plugs had this brown stuff on it and appeared to be smoking steam - leaky headgasket getting water onto the plug, but not leaking so as to mix the oil with water. A blast up and down the M40 seemed to have improved matters but I will have to have it done at some stage. £250 - 300 labour :? I'm sure it will be money well spent.
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Not too bad then really,once you start on the electrics it can be worse through the unknown
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Rocker cover ?
That would allow water to get onto the plugs ? This would be an interesting twist. What I noticed as well was that the 6 or so allen fasteners that secure the cover on the top of the engine - and go through mounting holes in the coils, do not appear to catch any screw thread and are mostly loose.
I'm going to have to get the Haynes book out to investigate the rocker cover possibility
That would allow water to get onto the plugs ? This would be an interesting twist. What I noticed as well was that the 6 or so allen fasteners that secure the cover on the top of the engine - and go through mounting holes in the coils, do not appear to catch any screw thread and are mostly loose.
I'm going to have to get the Haynes book out to investigate the rocker cover possibility
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My engine ( 104.92 ) has a camshaft cover. If water is contaminating the sparkplug at the electrode end ( around the gap ) would it not most likely be getting past the head gasket than any other seal ? I had the valve seals done in-situ on a former 190E but the symptoms of that was pushing oil past the valves into the exhaust - not letting anyting, like water, in.
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If water is on the end of the plug, then that is only via a head gasket and nothing else
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DelBenz
OK, now that you are starting to reveal more of the story/history leading on from your first post I would comment as follows:
1. With the loose top engine cover over the plugs, the action of steam cleaning the engine would cause water to get into the plug recesses.
That certainly could be contributing to misfire.
2. The "brown stuff" on the plugs which I thought may be oil from failing rocker cover seals, may indeed be the annular marks you get on plugs when the ceramic becomes loose from the plug electrode and gasses are forced from the combustion chamber.
You need to change out those plugs - make sure you put in proper plugs fropm Merc dealer - cost approx £1.90p each (non resistance type). Give your VIN to dealer parts person.
At the same time get 3 new "under coil extenders" at approx price of £9 each as they do go bad.
Unless you have new engine wiring loom on the car, be very very careful you only move the loom cables the absolute minimum as they go brittle and you will crack the inner insulation and cause expensive problems.
OK, now that you are starting to reveal more of the story/history leading on from your first post I would comment as follows:
1. With the loose top engine cover over the plugs, the action of steam cleaning the engine would cause water to get into the plug recesses.
That certainly could be contributing to misfire.
2. The "brown stuff" on the plugs which I thought may be oil from failing rocker cover seals, may indeed be the annular marks you get on plugs when the ceramic becomes loose from the plug electrode and gasses are forced from the combustion chamber.
You need to change out those plugs - make sure you put in proper plugs fropm Merc dealer - cost approx £1.90p each (non resistance type). Give your VIN to dealer parts person.
At the same time get 3 new "under coil extenders" at approx price of £9 each as they do go bad.
Unless you have new engine wiring loom on the car, be very very careful you only move the loom cables the absolute minimum as they go brittle and you will crack the inner insulation and cause expensive problems.
Sooner rather than later I'd say.
A couple of quick questions though.
Have you done a compression or cylinder leakage test yet?How much pressure is building up in the cooling system itself?
I only ask because from your original post it appeared that the fault was load related.Is it also apparent with the car in neutral or park?
A couple of quick questions though.
Have you done a compression or cylinder leakage test yet?How much pressure is building up in the cooling system itself?
I only ask because from your original post it appeared that the fault was load related.Is it also apparent with the car in neutral or park?
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No compression or leakage tests have been done. There is no excessive pressure building up in the cooling system - the hoses do not go hard, there's no oil or back pressure in the expansion tank, there is no sludge on the dipstick or emulsification under the filler cap. The temp when driving does not go much over 80 even when idling in traffic. When it starts playing up - normally in traffic with foot on the brake with it in Drive, it is still noticeable but not as bad when I put it into Park.
I don't want to be a party pooper,but a couple of things bother me here.
You obviously have a head gasket issue,the 'rusty' plug would confirm that.May I take it that you put new plugs back in?If so,has that improved matters?
Going along the lines that it hasn't improved,for the head gasket to cause this missfire,it would mean that the affected cylinder is loosing it's compression.I'm happy that the oil & water aren't mixing as it's quite common to just breach a water gallery.However,your cylinder compression would have to be going somewhere,which in that instance would be the cooling system,creating excessive pressure build up.
Please take this post in the spirit that it's intended.I'm not trying to pick a fight,we're just trying to help.You could spend a lot of money sorting out the h/gasket fault & still be left with a missfire.
