Northstar Engines and System Technical Discussion Discussion, '03 SLS - "Surges" at slowdown and stoplights in Cadillac Engine Discussion; I have a problem with my '03 Cadillac SLS. It "surges". It will run ok at 25+ mph, but on ...
I have a problem with my '03 Cadillac SLS. It "surges". It will run ok at 25+ mph, but on slowdown and stoplights it "surges". I have tried looking for vacuum leaks, all hoses in good shape - It reports a code of P0300. I change oil regularly and generally take good care of the care. It has 100K+ miles on it currently and I would expect it should go for more. I have also cleaned the throttle body and tried de-gunking the upper part of the engine.
One note...if I unplug the MAF sensor, it runs great. So I thought - hmm - bad MAF sensor. Tried replacing it....nope. Same problem with the new sensor. Any other ideas? I'm at my wits end and my wife refuses to ride in the car until I get this fixed
Automobile(s): White Diamond '03 DHS (with DTS floor shift)
Re: '03 SLS - "Surges" at slowdown and stoplights
Check the "plenum". It is the rubber coupler between the TB and the manifold. They tend to develop a crack on the underside where it can't be seen. Spray some Brakleen around it and listen for an RPM increase.
Sounds like the plenum to me also.....Remove the painted engine cover and look down in the valley where the throttlebody casting joins the plastic intake manifold. There will be a single rubber bellows-type connector, secured with a bolted plate at the TB end and a s/s clamp on the intake manifold. Spray a shot of starter fluid or brake cleaner under there.......you'll hear a distinct engine speed change if that's your problem.
Many, many posts on the replacement procedure......basically, the intake manifold gets tilted and lifted off after removing the injectors and fuel rail. Good time to clean the inside of the TB (TB cleaner ONLY), replace the plenum, clean everything, oil the injector O-rings, and replace the fuel rail. 2 hours.
Plenum is $40 +/-, dealer only, intake gaskets at any large parts house. Manifold bolts torque to 8 ft/lb in a crosswise sequence starting from the center two bolts in 3 passes.
Ok - I just did the test - removed the beauty cover, sprayed brakkleen on the underside of the plenum gasket while the engine was running (after a good warmup, of course) and viola - it had an increase in idle speed.
I called around and the plenum gasket is $26.31+tax and the intake gaskets about $14.00