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car shaking while accelerating

oozie51 oozie51
New User | Posts: 4 | Joined: 04/10
Posted: 04/22/10
06:40 PM

hello, i have a 1997 Chrysler Sebring Lxi with the 2.5 V6 engine. i have put more money into this car then anyone could ever understand. anyway, for about 6 months now this problem has seemed to be getting worse and worse. It started when i'd back out of my driveway, put it from reverse into drive, press on the gas to accelerate and nothing would happen. it was almost like it was flooding or something. if i eased onto the gas it was a little better, but it still did it. usually when i would hold on the gas for maybe up to 5 seconds or so it would suddenly "jump" and kind of put my head back in the seat a little bit almost like it suddenly received a jolt of gas and just took off. also, most of the time while idling at a stop light the engine would dog real bad. rpms would fluctuate and kind of get low. since then it has gotten worse. now when i'm coasting down a hill and letting gravity speed up the car it rides beautifully. but when accelerating, the car shakes like crazy, especially going uphill. its almost like the car is not getting sufficient gas to the engine. but it seems to be more than that. almost like it has more than one problem. i've replaced a ton of stuff. plugs and wires a few times. distributor and cap a few times. egr valve/silenoid, cat converter, fuel filter, belts, alternator, i'm sure i'm forgetting a few things. the car runs great otherwise, but it just dogs out very often and has starting shaking like a mutha F'er only when on the gas, especially uphills. please help with ANY suggestions of what this may be. thank you very much in advance. Smile  

waynep7122 waynep7122
Addict | Posts: 4545 | Joined: 08/09
Posted: 04/23/10
12:33 PM

you should probably print my answer.. so you can read it again .. its a lot .. but i have been fixing cars for 30 years...

i am going to advise you ... to get a OBD2 scan tool.... one that displays live data..  so you can examine the various data streams as they are happening..

you seem to have a lot of problems with that car... i am going to give you a few things to do first.. before buying the scan tool...
this is with the engine turned off

i know the battery is buried down deep in the front end...  but you are going to have to access it...   clean the cables with a stainless steel tooth brush from the hardware store.. you have to take the cables off the battery to do it..    

while you have them off at the battery..   follow each of the wires...   the negative cable will go to both the body and to the engine block...     carefully remove both of them .. one at a time. and wire brush the ring terminals , the back of the bolts.. and the place they are bolted to...

why the negative...   since the engine is sitting on rubber mounts.. it is not connected to the body or battery negative except through several ground cables... if these get dirty... the electronics will not have a proper source of power... remember.. electrons from from negative to positive..  so a loose or bad ground causes all kinds of invisible problems... that drive people mad...

if you have a digital volt meter.. you can do a test that takes about 2 minutes....

set the digital volt meter to 20 volt DC scale...

start the engine.. turn on the head lights...  

measure from the negative battery post to the engine block, you should get less than 0.04 volts..

measure from the negative battery post to the body.. you should get less than 0.02 volts..

measure between the engine block and the body.. you should get less than 0.02 volts..

if you get more voltage than that.. you have a bad ground..
this really does work.. but the engine has to be running.. and the headlights on.. as you can only do voltage drop tests with current flow through the measured circuit...


as for shaking..   how are the motor mounts...  how is the sub frame under the engine and transmission.. bolted up tight..

how are the CV joints..  i have had a TON of problem with the voyager series of mopars.. where the cv joints were bad.. and it would do a serious wobble  under acceleration..

how are your tires?????  are the steel belts separating?? does the car do the hula dance at 5 mph????  that would indicate that the tires have gone bad..

i have also heard of intermittent problems with the ECMs...

and the worst thing is the distributers in those motors..

the ignition coils fail..  they make spark.. but not enough to start the motor sometimes...   rebuild distributers usually have used coils in them.. and are cobbled together from cores to make a few good ones..

replacement ignition coils have started to show up in the aftermarket... standard ignition had a few listed .. they are deep in the distributer..

to test the coil output.. they have in most parts stores.. a under 10 buck tool...   not the one with the light in the clear plastic ..

this has an adjustable gap...  and gator clip spot welded to the adjusting screw. and a place to push a spark plug wire onto..

here is the part number for it..

Great Neck / Adjustable ignition spark tester
Part Number: 25069

here is a picture of it..  you will have to copy and paste..

so... clean the battery cables.. both ends.. check the spark...

examine the underside of the car..

the CV shafts might be the problem with it shaking only under acceleration..   usually not under coasting.. or at steady speed..

the harbor freight 98614 scan tool will display live data streams on your car...  so you can see what the sensors are doing. they get $139  but they do the same as the 199 and 300 buck units.. if not more.. i have one and i am happy with it..

oh.. bad grounds to the engine.. can also ruin wheel bearings and CV joints.. as the current from the battery is trying to get to the engine block somehow.. and the alternator output has to go the other way...  it burns the bearings  that need to be mirror smooth..  

fjbennett fjbennett
New User | Posts: 3 | Joined: 04/10
Posted: 04/25/10
10:33 AM

post 903  

oozie51 oozie51
New User | Posts: 4 | Joined: 04/10
Posted: 04/30/10
06:58 AM

thank you for the reply. the problem seems to have gone much further. yesterday while driving from school i was listening to the radio. first the radio started turning off and on by itself. then the car started like surging or jolting, then the battery light came on. i already had a new alternator put in and belt. battery is maybe a year old and is a real good one. something electrical?  

waynep7122 waynep7122
Addict | Posts: 4545 | Joined: 08/09
Posted: 04/30/10
05:33 PM

lets go in a different direction...

start the with replacement of the electrical part of the ignition switch...    the contacts do fail inside the switch.. and the switch is 13 or 14 years old...

autozone has them starting at 35 bucks...

the radio turning on and off...  and then the engine surging.. that is where i would start..

it is possible that something else in the power supply system is loose..

a bad ground wire..   a loose connection somewhere..

if the wires are loose... it will damage the alternators...

do you have a hand held digital volt / ohm meter  they start at 8 bucks.. you don't need to spend over 25 for one..

this test takes about 2 minutes...  quicker than it takes to type it or read it..

start the engine.. turn on the headlights...

set the digital volt meter to 20 volts DC scale..

touch one lead to the negative battery post..  the other to the engine block... you should get less than 0.04 volts

touch one lead to the negative battery post.. the other to the a ground on the body..  you should get less than 0.02 volts...

touch one lead to the engine.. the other to the body...    you should get less than 0,02 volts..

if you get any more than this.. you have a bad ground connection and that can cause all kinds of weird unseen problems..

post what you find..  

oozie51 oozie51
New User | Posts: 4 | Joined: 04/10
Posted: 05/06/10
05:40 PM

i was just checking out under the hood of my car and was inspecting my battery and the cables and all of that. then i noticed that before the negative cable goes to the negative terminal it appears to be grounded or something to the metal of the car. but while inspecting it i noticed that where its connected to the car (where it's grounded) it looks kind of cut or frayed. it also looks kind of corroded. would this have anything to do with the engine shaking when i accelerate and the radio turning off and on and all that junk? i also did a scan on the check engine light. i did the whole key turn trick to make the check engine light blink and give me the codes. first it gave me the number 12, which is just because the battery was unhooked. then it gave me the number 51, but not just once but twice. then gave me 55 which i think means the end of the code report. so i had a scan done on it and PO171 and like 174 or something came up. they were the same codes basically. something about mixture being too lean. so i heard something about the MAP sensor being bad so i replaced it. didn't fix a damn thing. i'm so lost with this whole thing. its to the point where i just need the damn check engine light to turn off so i can get it inspected. its already a month past inspection, i just hope i dont get pulled over. thanks again in advance.  

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