car lurches forward randomly while stopped
08-13-2006, 07:37 PM
#1
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car lurches forward randomly while stopped
ok, so recently my car has been acting kind of funny. It's only done it a few times now, so not sure what it is.
I'll be stopped at a stoplight or something, and when I ease off the brake (sometimes even when I'm just sitting there) the car just lurches forward, and I hear a little clunk noise.
this has happened 3 or 4 times in the past week. Was just wondering if this was transmission related or brake related?
I did notice something similar happen before, but it was when I was at a stop and I could hear the fans come on under the hood, then it would lurch forward if I wasn't giving it enough brake.
but the last few times it did it while the car was still cool and no fans were on at all.
I'll be stopped at a stoplight or something, and when I ease off the brake (sometimes even when I'm just sitting there) the car just lurches forward, and I hear a little clunk noise.
this has happened 3 or 4 times in the past week. Was just wondering if this was transmission related or brake related?
I did notice something similar happen before, but it was when I was at a stop and I could hear the fans come on under the hood, then it would lurch forward if I wasn't giving it enough brake.
but the last few times it did it while the car was still cool and no fans were on at all.
08-13-2006, 08:38 PM
#2
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Tranny or brake fluid, sounds like your tranny's slippin. Could be the master cylinder, but really sounds like the tranny has gotten worse
08-13-2006, 09:18 PM
#3
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yeah that's what I figured. I had a weird as slip between 3rd and 4th the other day. was just crusing in D4 and 3rd gear held a bit longer than usual, then it was just like NEUTRAL for a full second, then 4th caught. I just started laughing out loud after that.
good thing my dr evil trans is coming this week. I just hope I can pay my college fund back before I have to install it.
good thing my dr evil trans is coming this week. I just hope I can pay my college fund back before I have to install it.
08-13-2006, 09:42 PM
#4
how handsome I am
Originally Posted by ghost_masterCL
yeah that's what I figured. I had a weird as slip between 3rd and 4th the other day. was just crusing in D4 and 3rd gear held a bit longer than usual, then it was just like NEUTRAL for a full second, then 4th caught. I just started laughing out loud after that.
good thing my dr evil trans is coming this week. I just hope I can pay my college fund back before I have to install it.
good thing my dr evil trans is coming this week. I just hope I can pay my college fund back before I have to install it.
08-13-2006, 10:21 PM
#6
Loose Cannon
Sounds like it could be the idle air control valve to me.
transmission doesnt create any power, only transmits power that your engine is sending it, at idle, the engine should be smooth, if your a/c compressor kicks in, your rpms will drop causing the FI computer to up the fuel air mixture, causing the car to accelerate, the idle air control valve may be sticking closed causing too much fuel thus a surge in power, which is felt as the car lunging forward, if your transmission is that bad, that surge in power would be translated into almost no movement.
easy fix, carburetor cleaner all in your IACV. should help the vehicle be more stable.
transmission doesnt create any power, only transmits power that your engine is sending it, at idle, the engine should be smooth, if your a/c compressor kicks in, your rpms will drop causing the FI computer to up the fuel air mixture, causing the car to accelerate, the idle air control valve may be sticking closed causing too much fuel thus a surge in power, which is felt as the car lunging forward, if your transmission is that bad, that surge in power would be translated into almost no movement.
easy fix, carburetor cleaner all in your IACV. should help the vehicle be more stable.
08-13-2006, 10:35 PM
#7
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thanks lcstyle. I think that is exactly what it is, as it seems to have started around the same time that I started getting a weird vibration at idle. It was right about the time I installed my cams and I unbolted two mottor mounts when I did that, so I figured it was just some motor mounts bolted on uneven or something.
I think it happens both with and without the AC on, but not 100% sure. I will test that out.
I think it happens both with and without the AC on, but not 100% sure. I will test that out.
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08-14-2006, 01:42 PM
#11
contrarian in fashion
Originally Posted by WineRed2.2CL
motor mounts im missing them. what can this affect?
wait.........
is this a serious question????
08-14-2006, 01:46 PM
#12
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Originally Posted by WineRed2.2CL
motor mounts im missing them. what can this affect?
08-14-2006, 01:55 PM
#13
contrarian in fashion
im pretty sure he's gonna end up driving to work one day and he'll look in his rear view mirror and see his engine in the middle of the freeway
08-14-2006, 02:34 PM
#14
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Originally Posted by PimpCL23
im pretty sure he's gonna end up driving to work one day and he'll look in his rear view mirror and see his engine in the middle of the freeway
That would be priceless, i'd love to see that on vid
08-15-2006, 12:02 AM
#17
07 tl-s in
i actually drove my teggie for a month(125+) with two missing motor mounts and nothing happened,when i changed gears my whole motor jumped.I DON'T RECOMMEND THIS but i did it
08-16-2006, 05:45 AM
#18
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Originally Posted by lcstyle
Sounds like it could be the idle air control valve to me.
transmission doesnt create any power, only transmits power that your engine is sending it, at idle, the engine should be smooth, if your a/c compressor kicks in, your rpms will drop causing the FI computer to up the fuel air mixture, causing the car to accelerate, the idle air control valve may be sticking closed causing too much fuel thus a surge in power, which is felt as the car lunging forward, if your transmission is that bad, that surge in power would be translated into almost no movement.
easy fix, carburetor cleaner all in your IACV. should help the vehicle be more stable.
transmission doesnt create any power, only transmits power that your engine is sending it, at idle, the engine should be smooth, if your a/c compressor kicks in, your rpms will drop causing the FI computer to up the fuel air mixture, causing the car to accelerate, the idle air control valve may be sticking closed causing too much fuel thus a surge in power, which is felt as the car lunging forward, if your transmission is that bad, that surge in power would be translated into almost no movement.
easy fix, carburetor cleaner all in your IACV. should help the vehicle be more stable.
08-16-2006, 08:24 AM
#19
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Originally Posted by ghost_masterCL
wouldn't the idle speed fluctuate if this was the problem though? From lookign at the display on my VAFC it stays within 7 rpms of 750 rpms at idle. Does being in gear have any bearing on this? It seems to only happen when it's cold out (nighttime).
09-09-2006, 01:35 AM
#21
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just for reference, it was the transmission causing this. I gues teh torque converter wasn't "catching".
The weather has been getting colder here, and it is much more pronounced now. Sometimes when I'm at a complete stop and let off the brake it just sits there rahter than inching forward like uaual, then I give it some gass, it revs up then "catches" and jerks forward. Only happens a couple times when I first start the car in cold weather though. SAme thing with the 2>3 shift slip. only when engine is cold and ambient temp is cold.
The weather has been getting colder here, and it is much more pronounced now. Sometimes when I'm at a complete stop and let off the brake it just sits there rahter than inching forward like uaual, then I give it some gass, it revs up then "catches" and jerks forward. Only happens a couple times when I first start the car in cold weather though. SAme thing with the 2>3 shift slip. only when engine is cold and ambient temp is cold.
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