94 Seville SLS rough idle / surges / stalls
 

My '94 Seville SLS has developed a very frustrating problem. It idles very rough and surges; typically between 600 and 800 RPM. It doesn't matter if it is cold or warmed up. If the A/C is on and I stop ata stop light, the engine will likely stall. Once I get the engine over about 1,700 RPM, it runs quite well, like it always has. It is also hesitant to downshift when I stomp on the pedal, like there is no power,but once it does, it flies. The gas mileage has not changed noticeably. I still use premium fuel. A friend of mine insists that it has become gunked up as I mostly only drive about 1.5 miles each direction to work, so the car usually doesn't have time to truly warm up. He says it likely needs a valve job and thinks the cause isasticky valve(s).

I have changed the plugs, and wires, air filter, verified the PCV is not clogged. I can't find any vacuum line cracks / leaks. I've also tried using Lucas and other fuel additives for several tanks with no improvement. I was thinking of trying Sea Foam, but haven't yet.

The car has 135,000 miles on it. The codes in historyare: P039, P041, P052, P095, P103, P105, and P109.

All constructive suggestions are appreciated. :)

RE: 94 Seville SLS rough idle / surges / stalls
 

I haven't looked up the codes but you changed everything except the coils. That's where I putting my money. For another $20 change the fuel filter too. Once you isolate the bad coil(s) and fix them then take it out for a stomp.

RE: 94 Seville SLS rough idle / surges / stalls
 

Thank you Katzmans Caddy! I'll try both suggestions over the next week and get back to you with the results.

RE: 94 Seville SLS rough idle / surges / stalls
 

Katzmans Caddyrocks!

The fuel filter wasn't needed, but it never hurts to have a new filter. The coil serving the #2 and #5 plugs was weak. I even it put the old coil back on after the car started to idle smoothly just to make sure there is no doubt as to the cause of the originalidle problem. Sure enough, it was a bad coil! I have driven the Seville for two days since fixing the problem and it runs great. Yes, when I stomp my foot on the gas at 35 MPH, it downshifts and burns a little rubber, just like it did when it was new!

Thank you Katzmans Caddy, you're an Ace!

RE: 94 Seville SLS rough idle / surges / stalls
 

I am truly humbled sir by your kind words.:) It is always nice to help solve a problem and recieve such a nice report.:D Hope you enjoy your rejuvenated Seville. Isn't is nice to have all that power readily available under your right foot? https://www.cadillacforum.com/upfile...y/signs007.gif

RE: 94 Seville SLS rough idle / surges / stalls
 

Y E S !!!:)