1999 Deville I just purchased with 119,000 miles. Gave it a good performance test before I bought it, doesn't overheat and shifts OK. Was driving on Saturday and just exited a limited access road and came to the bottom of the ramp. As I made a right turn onto the intersecting highway I felt the power steering get very stiff. I realized the motor had stopped. Coasted at about 20 MPH and was almost stopped when I put the transmission in Neutral and turned the ignition key to restart the engine. It started immediately. When I checked the DTC codes I found a (CHANGED CODES)P1599 code which says the engine stalled or almost stalled. GREAT I KNEW THAT.
Other DTCs were present before. P1520 and P1527 I believe related to the transmission indicators not agreeing with the display. These were there before.

Now I'm afraid of the car stalling and dying somewhere far from home.

Any suggestions as to the cause of this problem? []BIGHANK

 

sounds like TPS is out of adjustment.

also, clear the codes and start fresh.

 

Check for carbon build up at throttle plate. Clean as nec. with air take cleaner(perfered) or carb cleaner. Clear codes as Stomper suggested see what comes back. Please post codes correctly there are no P5000 series codes.

 

Changed codes to P1520 P1527 and P1599 sorry about my faulty memory. Have cleaned my throttle plate on my C5 vette as well as the MAF sensor. Did that when I had some hesitation on moderate throttle and was accelerating but the LS1 never stalled just coughed. Where is the TPS?What do youhave to do to adjust, change,or clean it? Someone suggested a bad CKP sensor. Is that a possibility. No CKP codes set as of yet. Saw procedure in Haynes manual for changing the CKP sensor. Can this be done without taking the engine apart? Any suggestions on this?[]
BIGHANK

 

TPS is not adjustable, it attaches to side of throttle body and has 3 wire connector. Crank sensor(s) can cause it, but it is more common on 2000 and later models. P1520 and P1527 are transmission related. Carbon build up on throttle plate, IAC passages or valve itself, or EGR valve where valve sticks open are not uncommon causes for decel stalling at high mileage. Plug wires with excessive resistance routed too close to wires for ignition module another possible. Being very low on fuel(2 gallons or less) during hard braking and turning can cause it also.

 

lots of info here:

https://www.cadillacforum.com/search...archfor=faq%20

 

Will try cleaning the TB when it gets a little warmer. 12 degrees this morning. Where is the IAC valve. How do you clean or replace it? BIGHANK