Question about 1992 Cadillac DeVille

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I changed my fuel pressure regulator in my 92 sedan deville and now i get worse miles per gallon than before

Ive had my caddy a while now and at first was getting 16 to 20 mpg in town but as of lately it had dropped down to 11 miles then 10 miles when i looked up what could be causing this i was told that my fuel pressure regulator was possibly bad and should be replaced so i did that and now my car says im getting 6.9 miles per gallon and thats not cool at all any suggestions?

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  • Master
  • 2,101 Answers

The fuel pressure regulator will not do it. you need to look at spark plugs ,wires ,air filter, fuel filter. tires pressure if tires are under pressure can cause bad gas mpg

Posted on Jan 24, 2013

  • jwhyd
    jwhyd Jan 24, 2013

    yeah the spark plugs and wires are 4 years old at the most i put it in a shop to put the FPR on and it came out running worse than before, for some reason they turned my idle way up and i had to turn that down myself because it was making my car run badly and i figured that was why my mpg was so low but i turned it down and i went from 7 to 6.9

  • jwhyd
    jwhyd Jan 24, 2013

    when i look online it says it could be my o2 sensor

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Posted on Jan 02, 2017

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  • 39 Answers

SOURCE: 1991 cadillac deville .

did this happen overnight

Posted on Sep 22, 2008

3mac
  • 61 Answers

SOURCE: 95 sedan deville wont start and says fuel low with gas in tank

I'd start by tracing the fuel supply and return lines from the gas tank to the engine compartment. Make sure that they are free of kinks or other damage.

Next, check the fuse box and make sure there is power to the fuel pump. Trace the electrical connections leaving the fuel tank and make sure they weren't torn or otherwise damaged by the tire tread.

Hope this helps and good luck!

Posted on Jan 13, 2009

AskJack
  • 117 Answers

SOURCE: 1991 cadillac deville 4.9 fuel trouble

You just need to go through a simple Idle Relearn Process.

The Idle Speed Control motor will cause the accelerator pedal to tap and the car will surge back and forth, actually acting like there is a lack of power during intial startup.


Whenever a battery is changed, went dead or the ECM computer is replaced.

In order to make the engine run normal again, you need to take the car through a relearn process. Otherwise the idle could be very slow or have a 30mph idle.

To enable it to relearn, here's what to do.

1) Disconnect the battery cable for 15 minutes, before hooking it back up.

2) (KOEO) Turn the Key On with Engine Off, just so the electronics are on, but without starting the engine and turn the climate control panel to off.

3) Push the off and warmer buttons on the climate control panel at the same time and hold for up to 5 seconds for the computer to go into diagnostics.

On the fuel panel screen it will display 888 then E52 and then 70.

When it gets to 7.0 shut off the key for 1 minute.

4) Repeat step 3, two more times.

5) Start the engine without pushing on the accelerator pedal and let it run for 18 minutes with the climate control panel off.

6) After 18 minutes put your foot on the brake and shift into drive and wait 1 minute.

7) Then turn on the a/c by pushing the auto button. It needs to be warmer than 60 degrees F so the compressor can engage. Wait 1 more minute.

8) Put the shifter back in park and turn the key off.

9) Wait 1 minute

10) Idle relearn is now complete and the engine should start and run correctly.


Posted on Sep 16, 2009

ZJLimited
  • 17970 Answers

SOURCE: Firing diagram for 1990 caddy sedan deville front wheel 4.5?

To avoid confusion, remove and tag the spark plug wires one at a time, for replacement.
If a distributor is not keyed for installation with only one orientation, it could have been removed previously and rewired. The resultant wiring would hold the correct firing order, but could change the relative placement of the plug towers in relation to the engine. For this reason it is imperative that you label all wires before disconnecting any of them. Also, before removal, compare the current wiring with the accompanying illustrations. If the current wiring does not match, make notes in your book to reflect how your engine is wired.

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4.5L and 4.9L EnginesEngine Firing Order: 1-8-4-3-6-5-7-2 Distributor Rotation: Counterclockwise

Hope helped with this (remember rated this help) Good luck.

Posted on Nov 10, 2009

Kravcar
  • 192 Answers

SOURCE: I have a 1999 Cadilac Deville that I replaced a

Are you sure the thermostat was in the wrong way ?.

The thermostat is located in the bottom hose unlike most conventional cooling systems.

The thermostat in the Northstar engine is a dual action device.
One end of the stem is the Thermostat(obviously) and at the other end is a spring loaded pressure valve(the thinner end).

Make sure the thermostat end is nearest the rubber hose and the pressure valve end is in towards the engine.

Also note that the cooling fans don't come on until the coolant temperature hits around 225 degrees.
During normal highway driving the fans will very rarely come on(if at all) due to constant air flow through the radiator.They will only usually come on in heavy traffic conditions on a hot day.
But......if you have the Air Con switched on, the fans will run all of the time.

For overheating problems consider the following......

The most common overheating problem with the Northstar engine is a blocked purge line(small hose).The purge line is designed to purge air out of the cooling system.
There is a small diameter hose coming from near the top of the coolant tank (not the cap) ,this is the purge line.
With the engine idling,pull the purge line from the tank,if there is no coolant flow from this small hose,it is blocked and this will cause overheating.
If the hose is clear, check for blockage at the nipple on the tank.Or trace the hose back until you find the blockage.
The hose goes in to the engine to a crossover and comes out the other side close to the thermostat housing,the blockage may be there.

Posted on Jul 01, 2010

Testimonial: "Thank you very much for your help. The spring of the thermostat was towards the rubber hose and it was the wrong one. I did have a blockage in the purge line. I also found a small leak somewhere under the crosover pipe. This is my first experience with a northstar 4.6L engine. I realy like the car, I just got to learn how to take care of it. Thank you so much again for your help and if you can tell me any thing else I should know I would be forever greatful. Richard "

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1 Answer

93 deville burns alot of fuel, like a gallon a mile; no leaks in fuel line. Any suggestions?


A ruptured diaphragm in the fuel pressure regulator will let extra gas enter the engine through the vacuum line to the regulator. Pull off the regulator vacuum line. Any evidence of gas? Let the engine idle a couple of minutes with the vacuum line off. If any gas starts coming out of the vacuum line nipple on the regulator, then that was the problem. Replace the fuel pressure regulator.

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I have a '92 F-150. When it gets warmed up, it loses fuel pressure and dies. I changed the fuel pressure regulator and it got worse. Does anyone have any idea what may be causing this?


Put a pressure gauge on the FPR to see what the fuel pressure is. Could be a bad Fuel Pump, maybe even a fuel filter, but not likely.

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I have a '92 deville, and am getting concerned...


Check fuel pressure regulator. pull vaccuum line off and see if gas comes out. If so, that is likely part of the problem.

Also- if more than 75000 miles on injectors- replace them, you may have some leaky injectors. This is their expected service life.

IF in the odd chance you had one of the last carburated caddies, replace the choke thermostat and make sure idle step lever drops out of the way when warm.

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check for a leaking fuel rail,or injector,or the fuel pressure regulator,which is a vacuum operated valve at the end of the fuel rail.the high idle is caused by a vacuum leak,and if the regulator is leaking,that could be the fuel smell

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this is what I would do. I have the 1993 model and get 22.5 to 23 miles per gallon.
I would change the plugs, change the plug wires, change the fuel filter, change the air filter.
if you have done this lately then one overlooked item would be the coolant thermostat.

when you first crank the car and the engine is not warmed up, it runs in a "closed loop" mode and it gets bad mileage. the computer doesnt care about mileage at that point, it just wants it to run good.
after the coolant gets up to temperature, there is a coolant temperature sensor ( should be located screwed into radiator somewhere) that alerts the computer it is up to operating temperature. the computer then goes into a "open loop" mode and the computer then constantly changes the air fuel mixture to make the best out of emissions ,milage, and power,...
so, it it is not getting up to temperature it could be the coolant thermostat is stuck open. if you cant remember when the last time its been replaced then you may want to go ahead and do it.
if that dont work, it could be the coolant temperature sensor itself.
When I was carpooling in my caddi I drove 7 miles down the road to catch my ride. I get 15 miles to the gallon. and spend more on gas then if I just drove by myself. when I drive to work my self (35 miles) I get 23 miles to the gallon with stop and go averaging speed of 50

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1991 cadillac deville .


did this happen overnight

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