4.9 fuel injector confirmation
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Cadillac DeVille 1985 to 2005 including:
1985-1992 Fleetwood, 1993 Sixty Special, All FWD Forum Discussion, 4.9 fuel injector confirmation in Past Cadillac Vehicle Discussion; Am thinking of changing out the fuel injectors, after I do the O2 sensor and fuel filter. Just confirming as ...
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    91FleetwoodCoupe's Avatar
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    4.9 fuel injector confirmation

    Am thinking of changing out the fuel injectors, after I do the O2 sensor and fuel filter.

    Just confirming as I read this elsewhere; will the injectors from a 90s 5.0 Ford Explorer fit in our 4.9s? I believe it should be Bosch type III 19 lbs. I'm thinking of getting these: https://www.ebay.com/itm/271808080751

    One can find them labeled as for the 4.9 also but if they're labeled for a Cadillac of course they cost 20%+ more.

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    Ranger's Avatar
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    Re: 4.9 fuel injector confirmation

    Why are you changing the injectors? Are you having a problem?

    I traded my '92 (4.9) with 124K on it and never had to touch the injectors. Same with my '97 (4.6) and my '03 (now at 125K).

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    Submariner409's Avatar
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    Re: 4.9 fuel injector confirmation

    Yup ^^^ - if it ain't broke, don't fix it.

    Some subjective reason to suspect "dirty injectors" ? Either run a TopTier gasoline or pour in a 20 oz. bottle of Chevron TECHRON about every 5 - 6,000 miles.

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    basscatt's Avatar
    basscatt is online now Master of the Dark Art of Diagnostics
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    Re: 4.9 fuel injector confirmation

    Quote Originally Posted by 91FleetwoodCoupe View Post
    Am thinking of changing out the fuel injectors, after I do the O2 sensor and fuel filter.

    Just confirming as I read this elsewhere; will the injectors from a 90s 5.0 Ford Explorer fit in our 4.9s? I believe it should be Bosch type III 19 lbs. I'm thinking of getting these: https://www.ebay.com/itm/271808080751

    One can find them labeled as for the 4.9 also but if they're labeled for a Cadillac of course they cost 20%+ more.
    =================================
    here is what you really want - BOSCH - 4-hole - lifetime warranty - $92 - for the set of 8 - with free shipping -
    https://www.ebay.com/itm/BEST-UPGRAD...4AAOSwKMxbSrdZ

    slightly better power and slightly better economy -

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    Re: 4.9 fuel injector confirmation

    Yes, search around for the 4 hole bosch, matching set. I had a couple of oem injectors fail that i replaced with aftermarket. One of the replacements failed shortly after install so I decided to find a matched set of 4.9 refurbished. Google the injector rebuilder/cleaners to see who might have a matched set.

    You'll want a matched set so you have consistent spray volume for cylinders on each side. A unbalanced set of injectors would lead to too possible unburnt fuel in the cat.

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    Re: 4.9 fuel injector confirmation

    There seems to be a slight miss; under load like going up an incline periodically the engine will give a slight "burp" with a momentary noticeable power loss but quits it when I give it more gas, and the fuel economy is I suspect worse than it should be. Another Coupe Deville owner was looking at my car and told me there were no diagnostic codes, by the way, and there is no "new" problem; I've actually been wanting to change these for a couple years.

    Others around here have also suggested it's a good thing to do after changing the cat, which I've done recently, and that the upgrade should indeed help with the fuel economy. I suspected maybe even fuel was burning in the cat to cause it to clog the muffler, though one old shop owner told me it sounded like they were just due for replacement (143k miles and 28 years old). He was even trying to dissuade me from doing the injectors and doesn't want to himself at all but I've usually been right when I've wanted particular jobs done and other mechanics thought they knew better (most recently with the exhaust replaced). I looked at those ones as well bass.. thanks, will probably order them. Was quoted something like $200 for the job.

    I guess the issue could also be the computer. At this point if it's something that can be and hasn't been changed yet, it probably could use it is my thinking. The previous owner did nothing (distributor had original rotor and the factory 30k spark plugs were still in the car at 130k.. yet he had the transmission done ). I also found receipts under the seat for 87 octane fuel which I never used unless I was on the road and it's the only thing that was available, though even then my fuel economy never suffered at all but I did notice less power. I've also tried the Techron cleaner probably twice along with their 92 octane fuel.

    Funny enough I could probably make an offer on an '88 Eldorado for about what I'd pay for these injectors and the job but that's just another can of worms as it needs other work, but it does have the body style I've always wanted. I don't think I'm keen on paying for the same amount of gas and getting less power with the 4.5. Anyhow the Fleetwood is a damned reliable car as is though at this point I'd like to do what I can to keep her on the road in top running condition. Once I do that I can finally focus on the minor body and interior issues it has and perhaps keep her around as a weekend classic or finally consider selling it after having been asked "how much?" more than a few times already. Even if I don't get what I've put into her, I'd like to think that I did something to try and keep the car on the road in the time I owned it.

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    Re: 4.9 fuel injector confirmation

    Quote Originally Posted by 91FleetwoodCoupe View Post
    There seems to be a slight miss; under load like going up an incline periodically the engine will give a slight "burp" with a momentary noticeable power loss but quits it when I give it more gas,
    This sounds a lot like an ignition problem to me. I think if it where me, I'd change the cap and rotor first. The cap contacts point DO spark erode over time causing a larger gap for the spark to jump. If that doesn't help, I'd change plug wires. On second thought, since you said "The previous owner did nothing (distributor had original rotor and the factory 30k spark plugs were still in the car at 130k.", it might be worth simply doing a complete tune up (plugs, wires, cap & rotor) right off the bat.

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    Re: 4.9 fuel injector confirmation

    I've already had the the cap and rotor replaced with AC Delco as well as a Delphi ignition module. I had even bought a new Cardone distributor but since it was made in China I passed on having it installed. At the same time I also had installed Walker Thundercore spark plug wires and when they were put in a protruding wire caused a grounding out issue. Walker at the time offered to send me another set which I turned down having just spent a lot on labor having the tuneup done but I am now having them send them so will have them changed out to see what happens before proceeding with injector replacement. Mind you, the same basic issue was present even before that big tuneup was done and maybe around 12k miles has been put on since then. Basically everything was done except for the injectors. The car also has Bosch quad tipped plugs installed then.

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    Re: 4.9 fuel injector confirmation

    Familiarize yourself with the onboard diagnostic system for monitoring the sensors. It will provide a visual on when the cat is lean/rich, on torque lockup, and so forth.

    Also, there is a load test that allows you to test to see if each cylinder is firing. It entails installing a tach, and then turning off the injectors one at time to see a 50 rpm drop.

    I had a similar problem when one of my original injectors failed. Symptoms were slightly lower idle which was really evident during cold weather, as well as power problems at the higher speeds.

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    Re: 4.9 fuel injector confirmation

    Here's the script I keep in my phone:

    To enter the diagnostics system, simultaneously press and hold the OFF and WARMER buttons with the engine running until the system activates. Any diagnostic codes will display first. When the system prompts you with .7.0 you want to press the LO button. This will force the sytem to the PCM data mode and the display will show E.9.0 Use the HI and LO buttons to scroll thru the PCM data parameters. Here is what you can access....

    P01 throttle position in degrees
    P02 MAP (manifold absolute pressure) in kPa
    P03 computed barometer in kPa. Subtract MAP from BARO to get engine vacuum
    P04 coolant temperature in degrees C
    P05 MAT (manifold air temperature) in degrees C
    P06 spark advance
    P07 battery voltage
    P08 engine RPM....tach
    P09 vehicle speed MPH

    P12 injector pulse width
    P14 oxygen sensor voltage
    P16 oxygen sensor cross counts...a measure of O2 sensor activity
    P18 closed loop integrator (128 ideal...less equals leaning, more enriching)
    P20 closed loop block learn value (same as above)
    (Codes above this are unique to model/yr)

    When driving with the diagnostics activated the icons on the climate control panel stand for other functions....kind of like tell tales on an instrument cluster....

    rear defog is the VCC status
    front defrost is 4 gear status
    ECON is the o2 sensor status (on is rich)
    AUTO is the closed loop status
    OFF is the closed throttle switch status
    OUTSIDE TEMP is the AC compressor request
    F is the AC low pressure switch status
    C is the heater water valve status
    AUTO FAN is the cooling fan command status

  12. #11
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    Re: 4.9 fuel injector confirmation

    Thanks sefiro; that is indeed helpful.

    As to the spark plug wire issue, I have to say I am very impressed with Walker. I only contacted them again a few days ago about sending out the replacement wireset and just now received a FedEx package to Canada with the replacement set. Very good customer service!

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