Toxophilite

lurching 450

26 posts in this topic

I have a 2005 smart fortwo 450 CDI

Recently I repaired my fuel pressure sensor by adding another ground wire, initially with an  alligator clip to the block and now with a proper tapped in ground wire bolted to the ECU ground strap.

Last night (and before I did this final fix) I was heading up a hill and the car lurched quite dramatically (not unlike the sort of engineisgoingtofallout lurches cars make when they run out of fuel).

Today on a short 20 minute drive across town it did it a few times and a couple times on the way home, once quite dramatically. Not always on a hill but I would say definitely when accelerating.

Any idears?

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Hmmm....maybe remove new ground wire off ECU and put it on body ground and engine ground locations...?   Just to see....Just a thought....probably wrong but with these sensitive cars you never know?

 

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Posted (edited) · Report post

It started the lurch (last night) and was doing the lurch(early today) prior to me putting in the new ground fix. At that point it was alligator clipped to the block right by the fuel pressure sensor. I was hoping the lurch was the temporary ground being intermittent.

It is now firmly bolted to the chassis ground right above the intercooler(where I believe I was told the ECU grounds, it was also the closest)

I was hoping the permanent fix would stop the lurch but no luck

 

So really it could have nothing to do with my fix. I'm not sure though.

 

Edited by Toxophilite

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the ecu ground might not be the same as sensor ground

 

sometimes sensor grounds go back to ecu and are independent of common ground

 

...id be extra suspicious in situations where they dont just go ahead and use the sensor itself as a ground....

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Does your car sometimes lurch forward when clutch engages?  

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How many km are on the car, and when was the clutch last replaced? (Or is it on the original factory clutch?)

 

If it's lurching when a gear engages, it could be that the clutch actuator needs adjustment, or that the clutch itself is worn out. I remember mine starting to do that, and it was time for a new clutch, around 140,000 km if memory serves correctly.

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I did just replace the fuel filter water separator. I guess I might not have bled it. That was a couple weeks back.

 

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9 minutes ago, Toxophilite said:

I did just replace the fuel filter water separator. I guess I might not have bled it. That was a couple weeks back.

 

Did you fill it before reinstalling it?

 

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Is this happening while moving along? Or while accelerating from a stop? I would look into clutch actuator issues if its lurching upon initial acceleration.

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12 hours ago, Toxophilite said:

I did just replace the fuel filter water separator. I guess I might not have bled it. 

 

 

The fuel system self bleeds. After a filter change when you turn on the ignition you will hear all the ''gurgles!!''

Do that a few times and all is good!

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I must admit to not refilling it before reinstalling it. Maybe I have an airlock somewhere? It really does sound like the engine is almost just stoppping. Seems to be worse on acceleration . I mostly notice it while driving rather than froma  stop. It was doing it quite badly and repeatedly approaching my place today. At a stop light, I put it in neutral and revved my engine several times (No doubt intimidating the huge black pickup in front of me). It seemed fine then for the short little bit remaining.

 

The car has 79,00 km on it. 

It doesn't seem to happen during gear changes, more while accelerating.

 

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It is not clear to me what you mean by lurching. 

Does your Smart lurch forward uncommanded?

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No and yes. I'm driving and i think it's when i accelerate and it's like hiccups and feels like the back end is going to drop off. Feels like the sort of dramatic effect you sometimes get when a car runs out of gas or gets it's fuel supply cut off dramatically.

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That, in my humble opinion, is not lurching.  More like misfire. 

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Fuel pressure? Did it do it before you changing the filter? If not it's all related to what you touched. Retrace all the steps......did you install the seals? Is it leaking in any way? What are the hose clamps like? What about the hoses? Maybe take it off again and empty it, and shine a flashlight into the depths and see if you can see anything but fuel? Maybe the painful thing would be to buy another filter and try again?   Sorry.

 

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Well if anything I'd just put the old one back in as it looked perfect and din't have anything in it.

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Worth a try no...?    BUT, you'll never see the dirt inside a filter without cutting it open...seals? etc etc..?

 

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Posted (edited) · Report post

22 hours ago, Toxophilite said:

I must admit to not refilling it before reinstalling it. Maybe I have an airlock somewhere? It really does sound like the engine is almost just stoppping. Seems to be worse on acceleration . I mostly notice it while driving rather than froma  stop. It was doing it quite badly and repeatedly approaching my place today. At a stop light, I put it in neutral and revved my engine several times (No doubt intimidating the huge black pickup in front of me). It seemed fine then for the short little bit remaining.

 

The car has 79,00 km on it. 

It doesn't seem to happen during gear changes, more while accelerating.

 

Sounds like it's getting worse. I replaced my fuel filter before Christmas so don't remember the exact details but I'm wondering if you might be getting air in somehow or maybe have a restriction from a crimped or twisted fuel line.

 

Worse on acceleration/power demand could be an indication of that; is there a throttle setting that is below the trigger point for the lurching? Does it increase with power demand? Or is it a certain amount of power for a certain amount of time, i.e. more power triggers it faster than moderate power?

Edited by mender
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Curiously I can't get it to happen when the car is in neutral and I'm just revving the engine. Only under load and it has been getting worse in 1st and 2nd gear.

Tolsen is right, lurching implies jumping ahead, this is more of a dramatic hiccup/misfire where the car feels like it's dying very briefly

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How about simply bad fuel...?  Low octane..?

Contaminated...???

 

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I have had lurching in first gear upon takeoff in the past. It was caused by the actuator rod getting stuck in the hole in the clutch fork, and as it draws it back it bounces a little...  I could mitigate the issue by slowly pressing the accelerator until i was fully moving.. 

 

   I don't see how fuel could cause this issue. Even if it sucks in a small amount of air at a fitting etc.. it would maybe miss slightly.. but not lurch.  It would have to be a lot of air to cause an issue i think.

 

Have you inspected the clutch fork before??  80000km seems a bit premature for wear, but I would get a look.

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Posted (edited) · Report post

7 hours ago, Willys said:

How about simply bad fuel...?  Low octane..?

Contaminated...???

 

My cap was loose a few weeks back, and I do have a very nasty sneaky vengeful neighbour (in an apartment building) However one ones tries not to be paranoid.

Edited by Toxophilite

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1 hour ago, Toxophilite said:

My cap was loose a few weeks back, and I do have a very nasty sneaky vengeful neighbour (in an apartment building) However one ones tries not to be paranoid.

 

The fuel access door locks when the car is locked.  Unless you are leaving the car unlocked, there should be no way for the neighbour to mess with it.

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