What would cause a car to jerk?↕

[FoX]

My girlfriends car will take off but when she goes to start in first gear it acts as if all of a sudden it has no fuel... it does have fuel getting to it though i have verified that... I was thinking the Throttle Position sensor but am not exactly sure. Maybe even MAP sensor? I know we just replaces the themostat and the temp sensors and bled the air out of cooling system so now i am not sure.

[buds302]

i need more details. cant help if i have no details. do you mean from a dead stop or when she shifts into second

[jonrichert]

possibly fuel filters?

[justin89]

My girlfriends car will take off but when she goes to start in first gear it acts as if all of a sudden it has no fuel... it does have fuel getting to it though i have verified that... I was thinking the Throttle Position sensor but am not exactly sure. Maybe even MAP sensor? I know we just replaces the themostat and the temp sensors and bled the air out of cooling system so now i am not sure.
having air in the cooling system wouldnt cause jerking just overheating problem.more details would be nice,although the tps and the map sensor would have a cause for incorrect fuel delivery.it could tell the computer to add more fuel or subtract fuel.

[shepherd79]

make sure you connected the vacuum lines in proper order.

[gmech]

Fox - does the jerking occur only in first gear, at a low RPM in different gears or intermittently in all gears at various RPMs, when the engine is cold, etc?

[keruhas184]

My car jerks a bit when it deisels (runs too rich). The actual problem I haven't had time to pin down yet, but probably a vacuum leak or a faulty carb diaphragm.

[POS carb]

a stumble on acceleration from stop usually means a bad TPS or MAP sensor. On a carb it's usually a screwed up accelerator pump or nice vacuum leak

[Michael C.]

having air in the cooling system wouldnt cause jerking just overheating problem.more details would be nice,although the tps and the map sensor would have a cause for incorrect fuel delivery.it could tell the computer to add more fuel or subtract fuel.


DOES THE ENGINE LIGHT COMES UP? IF IT DOES.....CHECK THE CODES ON THE COMPUTER TO PINPOINT THE PROBLEM. THE COMPUTER IS LOCATED UNDER THE DRIVERS SEAT. BUT YOU CAN ONLY SEE IT BY MOVING THE THE SEAT ALL THE WAY FORWARD AND LOOKING FROM BEHIND THE SEAT (UNDER THE CARPET) :uh:

[buds302]

try runnin some fuel injector cleaner through it. you might have some clogged injectors. maybe the seals are bad where the injectors are mounted. is there any brown stuff where the injectors go into the intake. if ther is then you might need new seals. bad seals might be drawin air from the outside makin it run funny. if thats the case than the air is comin in messin with the map sensor(manifold absolute pressure)
basically its tellin the computer to add more fuel cause there is a change in the amount of air thats in the manifold. check all your seals and your gaskets. then take off the air intake system(the plastic shit) and with the car runnin put your hand over the throttle body hole. completly cover the hole. no air allowed to pass by. the throttle body is gonna try to suck your hand in. thats ok but if the car stalls with your hand over it then you have pressure. if it stays runnin even if it runs like ass then you have a leak somewhere. once you track down the leak you might be alright. but it dont hurt to try

[FoX]

Fox - does the jerking occur only in first gear, at a low RPM in different gears or intermittently in all gears at various RPMs, when the engine is cold, etc?


Mostly in the lower gears, at higher gears it seems to just hessitate once in a while... But usually it is worst when starting from a dead stop. No the Check engine light does not come on. I have already checked computer for codes, there are none. It is Fuel Injected not carb. Already checked vacuums and injectors... basically why i am at a loss...

[keruhas184]

a stumble on acceleration from stop usually means a bad TPS or MAP sensor. On a carb it's usually a screwed up accelerator pump or nice vacuum leak

You mean the throttle controller on the carb?

My car is really pissing me off now, as now the problem has gotten really bad. Basically the car runs fine up until some moment when the throttle doesn't respond at all! I mean you floor it and the rpms rise a bit and fall right away. To get the car to moving in at all I have to pump the accelerator like a lunatic with the car jerking like crazy. Its as though I have no low end at all, I have to try to rev it up to 5k to have the car to respond and start moving. After it gets real bad (totaly zero response from the accelerator) and shuts down and I start it back up, it works perfectly... :mad:

So its not the fuel filters/pump, and can't be ignition, because it would just work like shit all the time. I have a vac leak/bad diaphragm, and I'm thinking that throttle controller is the place to look...

[88Accord-DX]

TPS = Throttle position sensor
MAP sensor = Manifold Absolute Pressure sensor

The throttle postion sensor is opposite where the throttle baffle plate is on the carburetor. (either side of it) I would look into replacing it.

Since there is no trouble codes, I'm lost w/o looking at it in person. The fuel injectors could be not working problerly too, or they could be dirty. There are alot of variables when a car stumbles. I see you check for vacuum leaks. Try replacing the TPS sensor first, there is a test you can do on it, but requires a special diagnostic tool.