RPM's Dropping When Stopped At Light!!

ThunderCoupe94

Registered User
Wassup Guys? I know this is the best way to get nfo for my ride so i am asking here b4 i take it to the Stealership.. Everytime i stop at a light my rpm's just drop and then idles weird then they go right back up. If you know what this is please tell me its annoying the heck outta me. Please help me out.

Jayson
 
I Have The Same Problem

Jayson.........I hope someone has the answer. I have the same problem with my 94 SC except my RPMs do not go back up and the car just shakes and rolls. Have you noticed a drop in power when you accelerate? Some times the power is really there and other times I have no power with tons of boost. Mine ran terrible until I replaced the KNOCK sensor. It runs better now but is still not up to SC standards. Replacing the KNOCK sensor did nothing for the RPM problem.

Ed Springer

edspringer1@aol.com

90 Black Super Cougar 5 Speed (Highly Modified)
94 Red SC Auto (Working On It)
 
Sounds like you have a vacuum leak. This happened to mine. The hose that goes from the fuel pressure regulator to the intake plenum had dry rotted off. Check around the to make sure all your vacuum lines are there. My car would dip down to about 300 rpms at idle and the go back up to 700 rpms, but would never die on me.

Hope this helps,
Nick
 
i have a similar prob on my 90 aod...if i come to a stop light and slow down and stop (as you do at a stoplight heh (usually)) my rpms drop to bout 400 or so then pop back up and it idle's normally.

I assumed there could be millions of different possible causes for this...pulleys n belts are all fairly new on my car, plugs n wires, are all new, and it's a rebuilt engine and tranny so......

i guess the motor mounts could be the cause of this...but at the moment i'm not too worried bout that.

If you find out the prob though, i'd like to know what it was for you.
 
I had the same problem...at stop light,idle fell to about 400-450 rpm...replaced motor mounts when I added sway bars,now idles fine.Check the motor mounts.
z
 
poor idle

I had the same problem and was told about the motor mounts as well. I just got finished this weekend replacing them, and it idles incredibly now. The old mounts came out in 2 pieces... :confused: :eek: :(

One thing is for sure though, if you've never replaced the mounts on an SC before, be prepared for tough and sometimes frustrating job. It took me about 7-8 hours to do both. Good luck fixing the problem!
 
hey jay...is your car lacking power also especialy when taking off...try putting injector cleaner in your tank...good luck..
neil...
p.s did you change all the pullys?...your pullys were in bad shape....
 
How exactly do motor mounts have an influence on idle, is this just on automatics or does the same apply to the 5 spd?
 
I'm not exactly sure... there has been some debate on this issue. It is my theory that when the mounts collapse, the engine shifts position and binds the flywheel/pressure-plate (driveline to tranny). It does not seem to matter whether the SC is an AOD(E) or manual.
It will eventually cause a failure in the power steering line from chaffing.
 
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