» » »

Cadillac Q&A

Ask Your Question

2001 Cadillac Seville SLS Question: Service engine light keep popping up with error code P0171 and P0174.

 

Question

ranjit, Lees Summit, MO, October 17, 2012, 05:22
 Rookie

Repleaced MAF, PVC, air filter and checked for vacuum leak and found none. This weekend I am going to replace the Plenum boot between the intake manifild and the throttle control to make sure there is no leak.

When I raised the engine RPM pass 4000 I can feel one valve missing during the firing sequence.

Appreciate your help on this.

1 Answer
Flag This
  • Answer #1

    Greg's Orange Auto (13020 Answers) , Orange, CA - (714) 361-9386
    globalhelper October 17, 2012, 06:41
     Master

    this code can be very tricky to diag and repair at times. you most likely have a vac leak and on the 4.6l the boot does crack between thottle body and intake.when you remove it look on the bottom for small cracks or holes. if its ok i rec you get a smoke test which will show any vac leaks you have. ps repl the boot since it will be off and is suppect to leak at times

    Flag This
  • Reply

    ranjit, October 17, 2012, 06:49
     Rookie

    Thank yoo so much for your quick response. I did have the mechanic smoke test for vacuum leak and found one. I will check the Plenum boot. I have one more question, when I raise the engine speed rpm while the car is parked I can feel one cylinder speed hesitation. Do I need to chagne the park plugs or could it be a clogged injector. I did use the Chevron fuel injector cleaner and still the same proble.

    Thanks in advance.

    Flag This
  • Reply

    globalhelper, October 17, 2012, 12:35
     Master

    it might be related to the vac leak repair that 1st

    Reply
    Flag This