Fuel Injector Guru's, can you help?
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Cadillac DeVille 1985 to 2005 including:
1985-1992 Fleetwood, 1993 Sixty Special, All FWD Forum Discussion, Fuel Injector Guru's, can you help? in Past Cadillac Vehicle Discussion; Hello, first of all i'm a new member and would just like to say "hi" to everyone and thanks for ...
  1. #1
    85 coupe 5.0 is offline Cadillac Owners Member
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    Fuel Injector Guru's, can you help?

    Hello, first of all i'm a new member and would just like to say "hi" to everyone and thanks for trying to help me with my problem.

    I have a 1990 Cadillac Sedan DeVille, 4.5L "C" engine. It has a mean miss that comes and goes, and is getting worse. It's missing all the time now. I checked everything out sensor and code wise. upon inspection i found that i had one shorted fuel injector, it measured 3 ohms. I also found that there wasn't an injector that measurd greater than 15 ohms. The injector peak voltages weren't impressive either, with not a one touching 35 volts. It has the junk Multec 1 injectors with 150,000 on them.

    My question, what is the resistance on a good injector for this vehicle? I am ordering a set of replacement Bosch injectors for it, that way i can do away from the junk Multecs.

    Thanks!

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  3. #2
    85 coupe 5.0 is offline Cadillac Owners Member
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    Re: Fuel Injector Guru's, can you help?

    C'mon, you can't tell me that out of all the smart people here that nobody knows the resistance of a stock 4.5L Grey Top Multec injector?

  4. #3
    HippieD9 is offline Cadillac Owners Fanatic
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    Re: Fuel Injector Guru's, can you help?

    somewhere around 12 ohms is correct, I think. It's a good idea to replace 'em, especially since one has already went. That value will vary, but 3 is definatly toast. If you have any question, mail me. I've done this job before..

    D.

  5. #4
    85 coupe 5.0 is offline Cadillac Owners Member
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    Re: Fuel Injector Guru's, can you help?

    cool, thanks for the info. most of them are above 12 ohms, around 15 or so. but the #2 cylinder measures 2-3 ohms depending on temperature. I ordered a set from Linder Tech. today, cost $225.00 for all 8. They aren't the junk Multec's either, they are Bosch replacements. I have the injectors out, it was an easy task. Here is my next question, how do i perform the idle re-learn procedure without a scantool on this caddy?

    Thanks!

  6. #5
    inmycadillac's Avatar
    inmycadillac is offline Cadillac Owners Enthusiast
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    Exclamation Re: Fuel Injector Guru's, can you help?

    see that little toolbar under the cadillac forums greeting to you?? u know the one that says SEARCH!! go there and search "idle learn procedure" u will find enuff info there but since u are new to the site, I'll help u out here's a link:

    http://www.cadillacforums.com/forums...earn+procedure

    looks like our resident guru, BBOB, says it doesn't Need to be done, but if it makes u feel better, (like it would for me), disconnect the battery for like 30 seconds and then do the procedure

  7. #6
    85 coupe 5.0 is offline Cadillac Owners Member
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    Re: Fuel Injector Guru's, can you help?

    Thanks inmycadillac!

    I ordered in a new Multec injector and found the resistance to be 16 ohms for anyone else wanting to know.

    As for the idle learn procedure, it looks like BBOB was giving advice on a '98 model year vehicle in that post, mine is a 1990 and has the P.O.S little stepper motor under the hood on the throttle body. From what i am gathering there is a specialized learn procedure for cars equipped with this setup, unlike the OBDII controlled 1995 and up Caddy's.

    I have done a search and it has yielded nothing but confusion. Every post i find someone has something different to say. I am getting ahold of the factory service information Thursday when i go back to school, but would like to put the injectors in tonight and get it out the door of my shop.

    Thanks!

  8. #7
    BeelzeBob's Avatar
    BeelzeBob is offline I'm a Cadillac Fanatic!
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    Re: Fuel Injector Guru's, can you help?

    Why do you say the multecs are junk...??? After 14 years and 150K one of them fails...????....sounds like normal wear and tear to me....and someone maybe using a lot of injector cleaner or fuel system cleaner in their gas along the way. The solvents in the injector/fuel system cleaners will eat the insulation off the windings in the injectors (multecs, bosch, all of them....) and cause the resistence to drop as the coils short out. Almost every failed injector that I have ever seen is because of this.


    Regarding:""As for the idle learn procedure, it looks like BBOB was giving advice on a '98 model year vehicle in that post, mine is a 1990 and has the P.O.S little stepper motor under the hood on the throttle body. From what i am gathering there is a specialized learn procedure for cars equipped with this setup, unlike the OBDII controlled 1995 and up Caddy's.""

    The idle learn procedure is basically done for the same reason for all model years....it is to rapidly replace the idle learn values after a battery disconnect. The idle speed control system "learns" how much compenstation is needed to establish the idle speed desired and uses that learned offset as a reference point for the establishing the next idle event. The idle learn procedure will not "fix" anything and is not something that ever really needs to be done as the system learns on it's own all the time....the "procedure" just hastens the learning process for a car after a battery disconnect. It doen's matter at all to the car if the throttle body is clean and maintained...it is really for cases where the throttle body is dirty and the learn offsets are high as a result and then the battery is disconnected. If the high idle learn offsets are not replaced immediately there could be some stallling or idle surges as the system trys to compensate for the dirty throttle body.


    The little POS idle speed control motor sounds like it is working fine after 14 years and 150K.... why is it you label it a POS..???

    Have the throttle body bores and the backside of the throttle plates been cleaned recently??...and the EGR tubes...??? If not, then that would be a recommended maintenance item especially after that many years/miles. Hold the throttle blades wide open and clean the blades underneath and the bores of the throttle body below the blades. The EGR tubes are visible sticking up below the throttle blades from the floor of the intake. Those are NOT supposed to be full of carbon...rod them out all the way thru with a piece of stiff wire. Disconnect the negative battery terminal to reset those idle learn values after cleaning the throttle body to reset to the baseline values that are calibrated for a clean throttle body.

  9. #8
    85 coupe 5.0 is offline Cadillac Owners Member
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    Re: Fuel Injector Guru's, can you help?

    The Multec I's are junk. I used bosch replacements on this car. The bosch replacements don't let the fuel actually flow over the windings of the coil, unlike the Multec's. The Multec's in these caddy's have nothing but a history of early failure, 150,000 miles is an early failure. Most injectors are made to outlast the car, particularly the Bosh ones I installed. Look here, look at the repeated failures. This company does nothing but injectors and is very credible at what they do. Still don't believe me? Look at this bulletin identifying the problem with only the 1990 caddy's with the 4.5 "C" eng.
    It's an Adobe acrobat document. Look on page 14.
    http://www.lindertech.com/injinfo1.pdf

    Again, it singles out Multec's. Junk.

    Thanks for the info on the idle learn procedure, i was unsure of it, as i usually don't work on GM products and just wanted some info on the system, although it is somewhat familiar. The reason i call the stepper motor junk is because why couldn't they just use a pintle style motor instead of an external stepper? Again, it's just an opinion, i don't mean to offend anyone.

  10. #9
    85 coupe 5.0 is offline Cadillac Owners Member
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    Re: Fuel Injector Guru's, can you help?

    Oh, i forgot to mention, not just one injector was junk. Not a single one measured greater than 15 ohms, most were between 8 and 10 ohms. Specification was 15.5 to 16.2 ohms. They were all failing, none of them could produce a peak voltage greater than 30v either.

    The Bosch replacements are kicking up around 55v peak and are clicking nicely. All except for the #2 cylinder. The one that was previously shorted. Thanks to that shorted injector the computer quad driver for that injector is now burnt out due to the increased current flow from the low resistance. This car has been like this for a while.

  11. #10
    85 coupe 5.0 is offline Cadillac Owners Member
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    Re: Fuel Injector Guru's, can you help?

    Got the new PCM installed tonight, car runs like a friggin sewing machine again. Amazing that a dealership couldn't figure this one out, i mean c'mon, all it had was defective injectors and a computer, and on top of that this particular year and engine had a Technical Service Bulletin out on it about the injectors. *sigh* poorly trained technicians.

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