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1998 Deville
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710 Posts
Discussion Starter #1
I was helping a friend replace a radiator damaged in an accident a month or so ago in his 2005 DeVille. So we replaced it no issues and went to drive it. While on the test drive it drove really rough. Even revving it its rough. A lot of power gone, shook a bit, etc. I noticed the rough driving just moving it around my driveway to work on it before we ever started taking any parts off. He said it drove fine over to my house 2 weeks previous. It had sat for 2 weeks. We also smelled burning. So after our 2 miles test we were looking for the source of the burning smell and it seemed to be the catalytic converter. Looking under the car you could see it smoking from high heat. Also the check engine light was on and while the car was being driven it was actively flashing. We already knew that the CEL was on for a bad O2 sensor. And I know that a bad O2 sensor can lead to a making the cat go bad. So does 2+2=4 in this case?

The car was an insurance payout anyway (not totaled but he took the money instead of the repair) but we had hoped to get the radiator back so the car was drivable and then sell it for around $1000. It is in perfect shape otherwise. But with the bad cat it really is barely drivable and I am thinking perhaps even dangerous from the high heat.

Anyone want to confirm/deny or offer advice?
 

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Administrator
2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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68,392 Posts
The "bad O2 sensor" could have been caused by an excessively rich fuel mixture - FPR or sticky injector(s) - causing the cat to overheat.

Even a partially clogged cat should not contribute to slow speed rough running.
 

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White Diamond '03 DHS (with DTS floor shift)
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86,778 Posts
Yeah, hot, smoking CAT leads me to think leaky FPR.
 

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1998 Deville
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710 Posts
Discussion Starter #4 (Edited)
Here's the codes:

Current Codes:
P0424 Heated Catalyst Temperature Below Threshold (Bank 1)
P0429 Catalyst Heater Control Circuit
P0300 Random/Multiple Cylinder Misfire Detected
P0420 Catalyst System Efficiency Below Threshold (Bank 1)

But you are thinking the fuel pressure regulator?

FYI: I just went out and removed the vacuum line from the FPR while the engine was running and no sign of any gas at all coming out. Does this mean it is not bad or that just the diaphragm is ok?

http://www.amazon.com/ACDelco-12559037-Equipment-Injection-Regulator/dp/B000C9F55O/ref=sr_1_38?s=automotive&ie=UTF8&qid=1423412264&vehicle=2005-46-406------------9-0&sr=1-38&ymm=2005:cadillac:deville#productDetails
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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68,392 Posts
Good vacuum with throttle movements and no gas says that the FPR is OK. Now look at injectors and fuel pressure.
 

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1998 Deville
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710 Posts
Discussion Starter #6
The autoparts store tool has a good scanner. They can tell me what cylinders are having a misfire right? I think I can baby it to the store just a mile and a 1/2 away.
 

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Super Moderator
White Diamond '03 DHS (with DTS floor shift)
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Yes, most parts stores have scanners that can show the offending cylinder.
 

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Registered
1998 Deville
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710 Posts
Discussion Starter #8
OK I ran my Torque app with the OBDII blutooth plugged in that I forgot I had and it shows #2 cylinder is badly misfiring. Also shows #3 is misfiring but not as bad and also got a couple on cylinder 1. So I am going to move coil pack 2 to coil pack 4 location (swap them) and see if the misfire follows.

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What does the below mean? Are at least 2 and maybe 4 coils bad? I would be surprised to see them all go out at once seems very odd. What else can cause a misfire?

I also pulled 2 spark plugs and both had oil on them. Could have been fuel/oil mix.

This is what the scan tool shows:

cylinder misfires (car was running about a minute)
1 3606
2 154
3 1656
4 27
5 0
6 6
7 1
8 6
 

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1998 Deville
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710 Posts
Discussion Starter #9
So anyway. My handy dandy scanner app doesn't seem to get the correct cylinder for the misfires. We were taking off COP leads one by one and watching the readout and the 3 COPs on the front of the engine on the right most side are 4, 6 and 8, which are actually on the back. But cylinder 1 seems to be in the correct place. We're ordering an complete OEM bank (4 COPs plus harness - $137) and going to replace all of the rear ones. Then if any fronts are bad we will use the rear ones that are working to replace the front since fronts are easy. The best I can tell from the scanner is that 2 COPs are bad.
 

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98 eldo/KD54 w/N37,T96,QA1,D55,DS3,U1Z. U3R next
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2,125 Posts
Replace faulty coils, plugs, boots and springs. Replace upstream oxygen sensor. Check fuel pressure. Replace catalytic converter.
 

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1998 Deville
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710 Posts
Discussion Starter #12
His 2005 engine does not have boots and springs. Each long coil snaps directly onto the plug top.

You can find individual coil assemblies online.
Actually they don't snap on they just rest on the plug (spring pressure). We got in the new coil rail and will replace the entire rear one this weekend. Not sure we are going to replace the plugs the couple I took out look fine.
 

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1998 Deville
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710 Posts
Discussion Starter #13
All fixed! Replaced the back entire 4 coil unit. Not only that, I reset the CEL and so far it hasn't come back on. Car drives great again and scanner shows no misfires in any cylinders!

5 minutes to do the front 4, 2 hours for the back 4.

What a complete and total jerk that designed that. I mean what did they use a 1st year design student that took the course for an elective? Honestly this N* is the worst POS designed thing I've ever seen. Just the epitome of US corporate glut. Crap, crap and more crap.
 

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Super Moderator
White Diamond '03 DHS (with DTS floor shift)
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Hehe, I bet you invented a few new words doing this job.
 

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1998 Deville
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710 Posts
Discussion Starter #15
Yes I am sure I did. Just ridiculous. We opted to remove that "thing" with the hose on it from the top connection to the flexible metal pipe. No room at all to work. We dropped one of the screws putting it back but I found something close in my screw box so we just left it to wherever it landed on the frame. How in the world do they expect anyone to change plugs? We opted not to btw just the stupid coils. He just needs this car long enough so he can give his wife his new SRX, detail and sell her Mercedes, then get himself an XTS, then sell the DeVille.

Oh we also were fed up at the end and didn't put one of the screws to the bracket that holds the "thing". 2 out of 3 is enough!!
 

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2001 Seville STS, 1990 Seville (RIP), 1972 Sedan Deville
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26,323 Posts
The THING is one of the tho check valves for the A.I.R. system. An emissions system that pumps fresh air into the cat to help it reach operating temp quicker.
 
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