Motor jerks when I drive

Tiny
JER JER
  • MEMBER
  • 1997 FORD MUSTANG
  • 150,000 MILES
When I am driving my car and turn on the A/C my motor jerks, I took it to a ford dealership in my area and they analyzed it said the alternator and idle sensor needed replacing and I did that and it still does it?
Do you
have the same problem?
Yes
No
Wednesday, June 19th, 2013 AT 3:25 PM

6 Replies

Tiny
FREEMBA
  • EXPERT
Try this:
While the car is idling [in DRIVE, if it's an automatic otherwise neutral], turn on the A/C to see if it adversely affect the running of the engine. Listen for squeaks, rattles, etc.
Reason: The a/c compressor clutch may be locking up and placing an extra drag on the engine causing it to jerk.

How does the a/c perform? (Is it cooling normally?)
Does the engine every jerk when the a/c is OFF?
Was this
answer
helpful?
Yes
No
Wednesday, June 19th, 2013 AT 4:35 PM
Tiny
JER JER
  • MEMBER
Its a 5 speed manual freemba, the a/c cools fine and doesnt make any noises I can hear. The motor runs perfect without the a/c. The ford dealership I took it to said the a/c compressor all seems to be alright. I paid 170.00 for them to just analyze it on there computer and they wanted almost 800.00 to install the new alternator and idle control valve. After I heard that I took it back and did it myself for 260.00 in parts plus the 170.00 for there diagnostic which was obviously wrong. Grrrrr, it really makes me mad. Freemba, I am gonna take it to a a/c shop next to make sure the a/c is fine and ask about the a/c clutch. I was also wondering about a vacuum line or cracked intake manifold or something like that? The motor runs strong and its a fun Mustang GT, I really want this to get fixed cause I live in Florida and the heat and humidity here really sucks this time of year. Thank you for your reply and I will let you know how this turns out. Let me know what you think about the vacuum line or cracked intake. Thank you for your time brother. You guys rock.
Was this
answer
helpful?
Yes
No
Thursday, June 20th, 2013 AT 7:19 AM
Tiny
FREEMBA
  • EXPERT
Is the check engine light on on this vehicle?
I was thinking that this could be a ignition system problem [spark plug or wire, coil breaking down). Ignition system problems usually turn on the check engine light.

However, even if the light is not on, have the computer codes read at a local auto parts store; they will read them for FREE (finally something that saves money).
Don't buy any parts even if a code indicates a part as being the problem. Instead post the code(s) here for further assistance (often when a code indicates a certain part as faulty, that code could also be caused by faulty electrical connections or incorrect voltages, grounds, etc, or mechanical faults - so let's check it out first).
Was this
answer
helpful?
Yes
No
+5
Thursday, June 20th, 2013 AT 8:46 AM
Tiny
JER JER
  • MEMBER
The engine light only comes on only after I turn the a/c on and when it starts jerking? It goes off after a short while. Thanks for the heads up on a free computer diagnostic and I will do that today freemba. THANK YOU. I will be back with the code(s) soon my friend, I dont mind paying for work but when the ford dealership in my area (I wont say there name to be nice) tells me thats my problem and I do the work and save 500.00 for one hours labor (REDICULOUS) it is upsetting. Even the mechanic that worked on it and who I talked to told me one hours labor but the man at the counter quotes me the almost 800.00 bucks thats when I pull my car out of there. You have restored my faith in mechanics brother. Be back soon and thank you again.
Was this
answer
helpful?
Yes
No
Thursday, June 20th, 2013 AT 10:08 AM
Tiny
DSAND4520
  • MEMBER
I know this is old but did you ever figure this out? I have the exact same problem on almost the exact same car. Please let me know as this has been driving me crazy!
Was this
answer
helpful?
Yes
No
Wednesday, August 12th, 2015 AT 2:36 PM
Tiny
KEN
  • ADMIN
The jerking the engine is doing is probably becasue the engine is misfiring when the ac is on which is normal becasue the engine is under more load and the spark plugs are right on the edge.

I would start with a tune up and then go form there. Here is a guide hat will help you get the problem fixed.

https://www.2carpros.com/articles/how-to-tune-up-a-car-engine

Please let us know what you find ;)

Cheers, Ken
Was this
answer
helpful?
Yes
No
+3
Thursday, May 4th, 2017 AT 9:07 PM

Please login or register to post a reply.

Recommended Guides