Cadillac Owners Forum banner

1 - 15 of 15 Posts

·
Registered
2004 DeVille
Joined
·
5 Posts
Discussion Starter #1
Greetings guys,
Had my Deville for 3 years, and ran great until recently. It seems to act up more in the rain, but lately, it's constant. I've pulled all the codes and serviced, or replaced everything as needed. So far, I've replaced per codes:
TPS
IAC
Intake Plenum boot
Intake Manifold Gaskets
Water Pump
Fuel Filter
Fuel Pump (with new connector)

It would misfire, and have very little acceleration, and the condition got much worse in the rain.

I recently got it back from a dealership, and they recommended a new Fuel pump, because the pump was intermittently cutting on and off and causing the fuel system to go into OPEN LOOP. I replaced the pump with a new AC Delco unit, with the new connector, and that made the car run smooth as silk, but still had no acceleration. That was a week ago, and I've driven it hoping that the condition would get better, but today it got worse and misfired a bit pulling into my office, and has so little power that it almost couldn't back into it's parking spot.

Last night, I hooked a scanner to it, and pending codes showed Cat Inefficiency. I measured the temps of the Cat with an infrared thermometer, and the front flange showed just under 300 degrees, and the rear weld showed just under 600.

Any help or advice pointing me in the right direction would be greatly appreciated.
 

·
Administrator
2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
Joined
·
68,479 Posts
Your symptoms sure look like a bad cat.

You will need a bolt-in replacement that is certified for "50 state" emissions use. The lesser emissions certifications won't work - they set emissions codes.

RockAuto and/or Eastern Catalytic (maybe). Maybe www.nalley gmc.com.

How come you need Deville parts and your usename says "Fleetwood" ? Profile update ?
 

·
Super Moderator
White Diamond '03 DHS (with DTS floor shift)
Joined
·
86,785 Posts
Sure sounds like a clogged CAT.

CONVERTER OPERATION

Under normal operating conditions, the converter should not have to work very hard to accomplish its job. If an engine has good compression, is not sucking oil down the valve guides, and the fuel, ignition and engine management system are all working properly, there should be relatively little HC and CO in the exhaust for the converter to burn (a few tenths of a percent CO and less than 150 ppm of HC when the engine is warm). In many late-model engines with multipoint fuel injection, combustion is so clean that the converter has little to do and the difference between the inlet and outlet temperature may only be 30 degrees F at 2,500 rpm - which is a lot less than the old rule of thumb that says a good converter should show at least a 100 degree F difference fore and aft at cruise. At idle, the converter in many late-model vehicles may cool off so much that there's almost no measurable difference in fore and aft temperatures. So checking exhaust temperatures fore and aft of the converter at idle and 2,500 rpm is NOT an accurate way to determine if the converter is working properly or not.

One thing temperature measurements will tell you, however, is if the converter is working too hard. An infrared noncontact pyrometer or a temperature probe will tell you if the converter is running unusually or dangerously hot. If the converter outlet temperature is 200 or more degrees higher then the inlet temperature, it means the engine is running rich and there's a lot of CO in the exhaust that needs to be burned. A rich fuel mixture will often produce a "rotten egg" odor in the exhaust (the smell is hydrogen sulfide). Underlying problems may include an engine management system that is not going into closed loop (check the coolant and oxygen sensors, or for a thermostat stick in the open position), plugged PCV valve, or excessive fuel pressure (bad fuel regulator). High CO levels in the exhaust can also be caused by an inoperative air pump system.

If the outlet temperature is a lot hotter (more than 500 degrees F) than the inlet temperature, it indicates unburned fuel in the exhaust. The most likely cause would be ignition misfire (fouled spark plug, shorted or open plug wire, cracked distributor cap, arcing rotor or weak coil), or a compression leak (burned exhaust valve). But other causes may include lean misfire (check for vacuum leaks, leaky EGR valve, low fuel pressure or dirty injectors). A single misfiring spark plug can cause an increase in HC emissions of 2,500 or more parts per million, which can push the converter's operating temperature well above its normal range.

A common external clue of overheating to look for is a badly discolored or warped converter shell.

Source:
http://www.aa1car.com/library/converter.htm
 

·
Registered
2004 DeVille
Joined
·
5 Posts
Discussion Starter #5
Plot thickens! I hooked the Fuel Pressure Gauge to the Schrader valve last night, and here are the readings I got:
Key on, engine off - 42psi.
Engine on, idle - 32psi.
In PARK, with throttle, pressure drops steady to 10psi.
Driving, pressure drops steady until 8psi, at which point the fuel system reverts to OPEN LOOP.

tonight, I check the entire fuel pump harness, from the pump connector, back into the cabin, at the fuse box/pump relay...looking for an issue that may cause a voltage drop.

any thoughts?

----------

And for the record, While i did not put a vacuum gauge on the manifold, it does have good vacuum, and when I Pulled the vacuum line from the FPR, the pressure rose to 42psi at idle, but still dropped when accelerating.
 

·
Administrator
2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
Joined
·
68,479 Posts
Given your fuel pressure findings, it looks like new FPR time. Hairpin clip retainer, 2 O-rings must come out. Oil the new ones before slipping the new unit in at exactly the same orientation as the original.

made by Robert Bosch, Germany

In any event, somehow check/test the cat and exhaust backpressure (there should be essentially NONE at low-mid engine speeds)
 

Attachments

·
Super Moderator
White Diamond '03 DHS (with DTS floor shift)
Joined
·
86,785 Posts
I'm not sure that the FPR would (could) cause a fuel pressure as low as you are reporting. My money is on the fuel pump.
 

·
Administrator
2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
Joined
·
68,479 Posts
But how come pressure hops up to 42 psi, vacuum line disconnected in RUN ? Low overall fuel consumption ?

Hmmmmm................ pressure dropped while accelerating. Fuel pump module is worth a try.
 

·
Super Moderator
White Diamond '03 DHS (with DTS floor shift)
Joined
·
86,785 Posts
Yeah, I think a pressure drop when accelerating is a dead give away Jim. Especially when it drops that low.

P.S.
I am surprised that the engine even runs at 8 psi fuel pressure.
 

·
Registered
2004 DeVille
Joined
·
5 Posts
Fuel pump assembly was replaced about 10 days ago at Dealers' suggestion, along with new connector. (AC Delco unit, not Aftermarket).
Also, it also seems to happen worse when it's raining out, which leads me to believe that there's a voltage issue. Maybe a problem with the section of the fuel pump harness somewhere under the car between the pump connector, and the point that it enters the cabin near the back seat? Maybe a bad ground, frayed/chewed wire, broken/cracked connector, etc.

The car has air suspension, so when it's laid out, maybe it caught something in some grass, etc...

I"ll be inspecting tonight, I"ll report what I find.
 

·
Administrator
2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
Joined
·
68,479 Posts
It doesn't have "air suspension". It has normal strut/shock/spring suspension with air bladders on the rear shocks used as Electronic Level Control (ELC). The system compensates for extra weight in the trunk or back seat, using an air compressor, supply/vent control head, air lines and height sensors.
 

·
Registered
2001 Seville STS, 1990 Seville (RIP), 1972 Sedan Deville
Joined
·
26,323 Posts
I think he means an aftermarket setup. Look at the picture he posted several posts up. Plus the term "laid out".
 

·
Registered
2011 Crown Vic LX, 2009 Chevy Malibu 2LT
Joined
·
5,607 Posts
Fuel pressure regulator... These engine's weren't using a returnless system yet in '04? When did they switch it over?
 

·
Registered
2004 DeVille
Joined
·
5 Posts
Discussion Starter #14
It doesn't have "air suspension". It has normal strut/shock/spring suspension with air bladders on the rear shocks used as Electronic Level Control (ELC). The system compensates for extra weight in the trunk or back seat, using an air compressor, supply/vent control head, air lines and height sensors.
MoistCabbage is correct, mine has air suspension. :)
10641117_769988296395291_7459014282386829876_n.jpg
 

·
Super Moderator
White Diamond '03 DHS (with DTS floor shift)
Joined
·
86,785 Posts
Fuel pressure regulator... These engine's weren't using a returnless system yet in '04? When did they switch it over?
As far as I knew all the Northstars used a fuel return system, at least up to '05, but I could well be wrong.
 
1 - 15 of 15 Posts
Top