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1992 Eldo(RIP), 1975 LeSabre Cnvt, 2002 ETC ECS, 2009 CTS
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Discussion Starter · #1 ·
I have been going through my 1992 Eldorado, it has the 4.9 liter, and have changed the fuel pump, fuel pressure regulator, cap & rotor, wires, plugs, several vacume hoses, and still the car runs a bit rough, the idle is unsteady and when you hit the gas the car vibrates. I also am getting horrible gas mileage and black soot on the tail pipe tips. I did the PFI power balance test. According to the service manual, as I select each injector I am able to turn it off to check that its working. The engine rpm is supposed to drop when I turn off the injector, except all of mine cause the engine rpm to raise??? Has anyone had this trouble and what is needed to correct it? Any ideas would be greatly appreciated!
 

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2010 DTS
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88,013 Posts
Just a guess, but have you checked for the possibility of a stuck open or leaky injector.
 

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1992 Eldo(RIP), 1975 LeSabre Cnvt, 2002 ETC ECS, 2009 CTS
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12 Posts
Discussion Starter · #3 ·
I have been told that before. The power balance test is supposed to determine which injector is the culpret. As i stated above, the engine rpm is supposed to drop as I turn off each injector, the one that has no change is supposed to be the bad one, but i never get that as I do the test. Do you know another way to find the leaky/stuck injector? Thanks for the idea Ranger.
 

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2010 DTS
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The only way is to pull the fuel rail with the injectors attached. Then turn the key on (DO NOT crank the engine) to energize the pump and pressurize the fuel rail and look for a leaky injector.
 

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1992 Eldo(RIP), 1975 LeSabre Cnvt, 2002 ETC ECS, 2009 CTS
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12 Posts
Discussion Starter · #7 ·
Thanks again Ranger, I will try that when I can.
 

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1992 Eldo(RIP), 1975 LeSabre Cnvt, 2002 ETC ECS, 2009 CTS
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12 Posts
Discussion Starter · #8 ·
I put 8 reman injectors in and the car is a little better, but still with the vibration and sluggish acceleration. Any other Ideas???? This is driving me nuts, car ran perfect, then one day she started to run a little rough and lost power and smoothness in acceleration. I changed many different parts, no error codes in the computer, no service engine soon light. Car has new fuel pump, pressure regulator, filter, injectors, ox sensors, cap and rotor, bosch +4 plugs, wire set, tires, many little vacume lines. Any ideas would be helpful. I have the factory service manual, some vibration diags lean tword the transmission. I changed the fluid and filter in the trans, minor improvment. Each thing I have changed made a small improvement, but the car still isn't running correct.
 

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2011 Crown Vic LX, 2009 Chevy Malibu 2LT
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5,607 Posts
Black soot out the tailpipe is not a transmission problem. The vibration is almost certainly a misfire issue.

When did you first notice the problem? Has the timing been adjusted recently?

Do you know how to use the onboard diagnostics? Taking a look at what the PCM is doing with the fuel trim could give some leads.

-Press and hold OFF and the RED warmer buttons on the climate control panel.
-Let the system go through it's check.
-When it displays "PCM?", press up on the FAN button.
-If the display shows "PCM DATA", press up on the FAN button again. If it doesn't display "PCM DATA", press FAN down button until it does, then continue.
-Press up on the FAN button to cycle through the data. View PD38 and PD39, and report their numeric values in this thread.
 

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1992 Eldo(RIP), 1975 LeSabre Cnvt, 2002 ETC ECS, 2009 CTS
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12 Posts
Discussion Starter · #10 ·
I do know the on board diagnostic computer fairly well. I love that it shows fault codes and you can test just about everything in the car. A friend of mine suggested I put a new ground from the body to the engine. I did just that, and the car runs the way it shoulld. No more vibration, smooth acceleration. Thanks Drewsdeville for the suggestion, I am going to look and see what the data says out of curiousity. Thanks again to all those who have written me with help. "They don't make luxury cars, they make Cadillacs!"
 

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1992 Eldo(RIP), 1975 LeSabre Cnvt, 2002 ETC ECS, 2009 CTS
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12 Posts
Discussion Starter · #12 ·
Thanks again Ranger. Any particular brand or type that you would suggest? I was thinking back to AC Delco, something platinum.

DOWNLOW (I Cant send private messages yet) asked me about the ground that I made, he has a 92 Seville with what sounds like the same problem I had. The car vibrates when hitting the gas. I do recomend you check the fuel pressure regulator. Take off the vacume line and see if any fuel is in the line or the vacume port. If there IS it is BAD. Replacement was fun, I suggest takine out the fuel rail if you dont have the special tool Torx 30 "J" wrench. As for the ground, I took two 12 inch pieces of 14 gauge wire stripped both ends, tied them together and crimped a large ring connector, the 12 gauge size (yellow crimp) on both ends. Basically a double wire with a ring at both ends. I connected one end to the nut on the alternator, pulley side on the left, closest to the strut tower. I connected the other end to one of the strut mount bolts on the top of the strut tower. Let me know how you make out. Feel free to ask any questions. Good Luck!
 

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Super Moderator
2010 DTS
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88,013 Posts
Sorry for the late response, but I lost my internet connection for several days.

I'd go with whatever A/C Delco plug us called for in your owners manual. It's probably a 4.9 I assume and I don't recall what plug that engine calls for.
 
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