Tach Jumps when stopped, Rough Idle... HELP!

[abo420]

So heres the problem, 94 Eldo 75K, When I come to a stop at a light the tach will start to jump. it bounces from 500 to about 750rpms and back to 500. The car will shake a little and seem like it might stall but never does. When this happens the car pushes forward a little so I have to keep firm on the brake. When this is happening and I start to roll from a stop, it will hesitate a bit, but everything is fine once I get going. Intermitten problem. My first thought was plugs and wires. Got them direct from Cadillac but the problem is still there. So now I turn to you guys, any help would be greatly appreciated,
Thanks Guys!!

[wydopnthrtl]

The computer adjusts idle speed to some degree by adjusting timing.

I wonder if you have a bad crank position sensor? Or maybe a corroded connection to it?

See if someone can data log your timing at idle when it's doing this. (I can do this with autotap)

Rich

[whack_lac]

Do you get any codes? Possibly a sticking egr valve. That would cause the engine to rev like that. Theres a tutorial on here for cleaning it, but you'll have to search for it. I'd post the link but I'm on dial-up right now and don't have the patience.

[abo420]

No Codes, and that's just adds to my confusion but both are good suggestions or places to start

[Ranger]

Lift the intake manifold cover and rod out the EGR "mouse holes".

[nitehawk1m]

I read your post and it sounded just like mine earlier in the forum. First suspect was the EGR valve. I took it to the dealer and it turned out to be the fuel pressure regulator. HAPPY MOTORING AGAIN!!!!!

Ed