: 2004 DTS Frustrations... misfires and SES



BlackLac96
03-08-14, 09:11 PM
Good evening everybody. I have utilized this site to fix MULTIPLE issues on my Caddy's over the years and now have reached a brick wall with my current 2004 DTS w/125K miles. I purchased the car and soon after it developed a misfire at Low idle. It is very noticable at lower idle and under a load, however when you hit the accelerator it smooths out. I researched this site and made sure the engine had the improved head bolts (thanks to previous posts JKA is the engine code) so I should be good there. It's been sitting since last October and today was the first day I had a chance to tackle what I thought was the problem due to the Antarctic freeze we've been in up north. It's throwing codes P0141, P0300 and P0357. I know the 0300 is multiple misfires, 0357 is the 7th cylinder for the coil and the P0141 is the oxygen sensor (this is probably thrown due to the misfire though). Here's what I've done:
*Replaced all rear coils with the ACDelco genuine replacement
*Replaced all plugs with genuine recommended ACDelcos (the previous owners used the Autolites-ugh)
*Sprayed Ether around the intake/throttle area to see if it was leaking-idle did not change
*Checked the OHM rating of the fuel injector on cylinder 7 it was above 14 I remember.
*Cleared the DTC codes

It is still misfiring and after clearing the DTC codes the SES light was blinking and threw the same codes. When I changed the plugs they were not fouled or anything even in cyl 7. I did notice today when I held the accelerator at 3000 RPM there was smoke coming from the exhaust not coolant smelling but oil/rich gas smell. The coolant level is fine and the car did not overheat. I'm hoping any of the experts can steer me in the right direction! Thanks ALL for your help ahead of time. -J

MoistCabbage
03-08-14, 09:16 PM
Since you're smelling fuel, I'd check for a leaking FPR, and then a sticking/leaking injector.

With the engine cover removed, engine idling, disconnect the vacuum line from the FPR (on the fuel rail). Any raw fuel at the nipple indicates a ruptured diaphragm - Faulty FPR.

BlackLac96
03-08-14, 10:11 PM
Thank you for the quick reply. I will try this out tomorrow. This may sound obvious but the cylinder 7 injector would be the only one in question correct then? Thanks!

Ranger
03-08-14, 10:23 PM
Injectors are pretty reliable. That would be my last suspect.

BlackLac96
03-09-14, 02:27 PM
I checked the Fuel Pressure Regulator this morning and it was completely dry. Any more suggestions would be greatly appreciated as I'm at wits end with this car. Thanks!!

Ranger
03-09-14, 03:32 PM
You said you "Sprayed Ether around the intake/throttle area". Did that include the plenum duct and if so, did you flex it near the bottom while you sprayed it?

BlackLac96
03-10-14, 07:16 PM
Ranger, are you referring to the rubber piece between the throttle body and plenum? I did spray around that area with no change to the idle but I did not flex it.

MoistCabbage
03-10-14, 07:20 PM
Try again while flexing it.

Ranger
03-10-14, 09:43 PM
Yes, that is what I was referring to and :yeah:

Submariner409
03-10-14, 09:58 PM
Here's what you want to use a LONG screwdriver to carefully flex ............
down in the opening near the IAC and fuel line quick connects .........

BlackLac96
03-10-14, 10:24 PM
Thanks all. I am planning on tackling this tomorrow...will update.

98eldo32v
03-13-14, 10:56 PM
When you replaced the coils, did you replace the boots and the springs also?

99Classillac
03-14-14, 03:37 PM
Without flexing the plenum, it's hard to get it to suck up the ether. Also, check the pcv valve hose at the end of the intake(opposite side of where the plenum is). It dry rotted on my 04. I used regular old fuel line to replace it. The intake manifold has to come out though. Just a suggestion though, I just had it happen to mine a while back.

1copenhagen
03-16-14, 01:14 AM
the PCV hose can be replace by removing the power steering pump took me less than 15 min. to replace it on my 05 deville the pump has 1 13 mm bolt that holds it on after you remove the belt a curved long nose needle nose pliers will help

BlackLac96
03-29-14, 09:56 PM
Update: spent the morning tearing the car apart lol but was well worth it. Our weather up here has prevented me from tackling the problem. The rubber elbow behind the power steering pump to the intake was dry rotted and had a hole in it. I couldn't see this with a flashlight. I also ordered a new plenum as the other one seemed stiff like the rubber was about to rot, plus I already took the intake off. Hopefully this will solve my problem. Again I would not have solved this without the help from this forum. I think this vacuum leak was the root of all evil on this car lol.

Submariner409
03-31-14, 06:20 PM
Look through my albums - lots of stuff (6 pages) on the 2002 Northstar - close in many ways. The Community tab, Albums, the red Seville - two albums together.

Mark C
04-03-14, 05:59 PM
P0357 is not a cylinder 7 misfire (it is, but not how you would think of it), that would be P0307. Its a Ignition Coil 7 Primary/Secondary Circuit Malfunction. either way it looks like you have an issue with cylinder 7 coil and probably need a new front coil pack, might get away with just a new ICM module for the coil on the front head.

BlackLac96
04-05-14, 05:23 PM
Well...I guess it's time for the stealership unless there are a few parting words lol. I replaced both the vacuum elbow on the intake and the plenum with a new one. Cleared the codes and started the car and it's not running rich or burning oil anymore but it threw the same codes again...ugh. I cleaned everything, including the throttle body, I even swapped an injector to eliminate that as a possibility but it's still throwing the P0357 and P0300 and the engine misfires/shakes at idle/low idle. What was also weird today was it threw an airbag code relating to the rear right sensor...strange.

Submariner409
04-06-14, 12:13 PM
P0357 is not a cylinder 7 misfire (it is, but not how you would think of it), that would be P0307. Its a Ignition Coil 7 Primary/Secondary Circuit Malfunction. either way it looks like you have an issue with cylinder 7 coil and probably need a new front coil pack, might get away with just a new ICM module for the coil on the front head.

Cylinder 7 is on the right (rear) bank.

BlackLac96
04-06-14, 10:37 PM
I did replace the plug and coil pack with genuine AC Delco...no change...