4.5L Deville runnability issues/ emissions problems
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  • 2 Post By Sevillian273
HT4100 4.1, 4.5, 4.9 Discussion, 4.5L Deville runnability issues/ emissions problems in Cadillac Engine Technical Discussion; As stated in the title I am having problems with my 1990 Cadillac Deville with 140k miles. The problems started ...
  1. #1
    nfakbc is offline Cadillac Owners Member
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    4.5L Deville runnability issues/ emissions problems

    As stated in the title I am having problems with my 1990 Cadillac Deville with 140k miles. The problems started with a hard cold start but then it would run fine to a hard cold start with when warm a rough idle and hesitation. I read that these cars are known for having a bad engine ground to chassis which I replaced and helped with the driveablity issues.

    My new issues are although the car seems to run fine it will not pass emissions and seems to be severely lacking power (cuts out/ misses at higher rpm's). Other than replacing the engine ground I also made sure for spark on each cylinder, timed the motor, cleaned the egr tubes under the throttle body and threw a wideband o2 sensor (innovate LM2) on the car. My air to fuel ratio at idle is a very rich 11.8-12 to 1, seems fine cruising at 14.5-14.7 to 1 and goes lean at 17+ to 1 under hard acceleration.

    I tried a different map sensor with no change but also noticed the idle control motor never moves. I also checked for vacuum leaks which found a few questionable connections which I repaired. I pulled codes and came up with E53 - Distributor Signal Interrupt.

    I'm really unsure what to check for next which is why I'm looking for your guy's help. Any advice would be very appreciated!!!!

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  3. #2
    Sevillian273's Avatar
    Sevillian273 is offline Cadillac Owners Connoisseur
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    Re: 4.5L Deville runnability issues/ emissions problems

    Ohm out the injectors, that might give you a clue. Should be 12 - 17ohms. Its best to check them when hot.

  4. #3
    drewsdeville's Avatar
    drewsdeville is offline Cadillac Owners Master
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    Re: 4.5L Deville runnability issues/ emissions problems

    In which area does the car fail emissions?

  5. #4
    nfakbc is offline Cadillac Owners Member
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    Re: 4.5L Deville runnability issues/ emissions problems

    I just got done measuring the resistance on the injectors. They measured on the front bank 6.8, 11.8, 6.6 and 9.9 ohms and on the rear bank 2.2, 2.6, 3.3 and 9.9 ohms. They were all replaced a few years back.

    On the emissions side it failed on both HC idle (247 with a limit of 220) and CO idle and cruise at (1.18 at cruise with a limit of 1 and 6.95 and idle with a limit of 1.2)

  6. #5
    Sevillian273's Avatar
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    Re: 4.5L Deville runnability issues/ emissions problems

    Jeez well theres your problem... Those numbers are WAY too low and such low resistance can overheat the computer if you leave it alone. Your injectors are acting intermittently and as the coils deteriorate, the resistance will go even lower and they will stop working altogether. The factory units were notorious for coil failure.

    http://www.lindertech.com/dirty_dzn.htm

    You will read on this forum about using ford bosch injectors - they are not for the 4.5. They will work but it will run rich and mpg will suffer (~15mpg) The 4.5 uses 16lb/hr injectors vs 19lb for the 4.9L.

  7. #6
    daniel58 is offline Cadillac Owners Fanatic
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    Re: 4.5L Deville runnability issues/ emissions problems

    It could be the injectors but they are very expensive for a could be problem. I have recently had a problem similar to this with my 4.5 Deville and after spending a small fortune and 6 months of work it turned out to be a defective NEW Bosch O2 sensor. An O2 sensor is a lot cheaper to try than replacing injectors right off. You may want to try injectors from a junkyard first just to see if they help. Sevillian is correct that the 19# injectors will not work in your 4.5. I tried Venom 19# injectors and they definitely will not work. With that E53 code you might want to check for loose connections and bad wires in the distributor also.

  8. #7
    Sevillian273's Avatar
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    Re: 4.5L Deville runnability issues/ emissions problems

    Quote Originally Posted by daniel58 View Post
    It could be the injectors but they are very expensive for a could be problem.
    With those low resistance figures, its not a 'could be'. The only one that is close to acceptable is the 11.8. The rest are junk. I agree E53 is part of the problem but regardless of anything else, those numbers are way too low.

    Sevillian is correct that the 19# injectors will not work in your 4.5. I tried Venom 19# injectors and they definitely will not work.
    I've run a few sets of 19's on my 4.5 and they WILL 'work' but mileage will suffer big time and the fuel data center will be grossly innacurate.

    A set of 19's will get you by in a pinch. They are alot cheaper and more readily available. Ive bought 3 sets of them out of mustangs and ford explorers from ebay for $30 to $50 and all tested good. I've read that the Venom brand are of low quality and their flow rates differ from unit to unit.

    Im working with a set of BMW injectors that may pass as an alternative to using the factory 16lb injectors. After a couple tanks of gas and a new EGR valve(unrelated) I will post the result.

  9. #8
    daniel58 is offline Cadillac Owners Fanatic
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    Re: 4.5L Deville runnability issues/ emissions problems

    Well, I will give you that one Sevillian the Venom injectors are notorious in other forums (Toyota Supra)for being hard to control. Even with racing computers that allow you to dial them in they are all over the map and uncontrollable and it gets worse with a bad O2 sensor. In my situation they were incidental, the O2 sensor was the original problem, just trying to pass that info along. My injectors OHMed out good though so bad injectors may very well be the problem here. They are so expensive however, you want to be sure that is the problem before spending so much money.

  10. #9
    Sevillian273's Avatar
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    Re: 4.5L Deville runnability issues/ emissions problems

    I'll say it again: Resistance below 12ohms on a high impedance injector is unacceptable. There's no question there.

  11. #10
    bloodyknuckles is offline Cadillac Owners Member
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    Re: 4.5L Deville runnability issues/ emissions problems

    4 year later i will have to agree with sevillian on this one. If you have the 4.5 liter with the original injectors, definitely test them. more than likely they will be out of range and you will have to replace them. I bought a set of 8 refurbished [B]Bosche Type II[B] injectors, and my fuel efficiency got up to 30 MPG HWY. got the recommendation from a Mr. injector website, and my caddy ran like it has never ran before. also read an article about how the original injectors were not designed properly and could not handle the heat where the ports are. I would yank the whole fuel rail to get to the injectors if you suspect them. ENJOY.

  12. #11
    Sevillian273's Avatar
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    Re: 4.5L Deville runnability issues/ emissions problems

    Performance-wise, the OEM injectors are hands down THE best ones. The fuel atomization from them is unparalleled compared to any other design I've tested, even better than the highly praised 'Bosch III' injectors. The only trouble is getting a good set that lasts...
    drewsdeville and drewsdeville like this.

  13. #12
    drewsdeville's Avatar
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    Re: 4.5L Deville runnability issues/ emissions problems

    Agreed, 100%. The Multec design is the best out there, mechanically. Their Achilles Heel is longevity of the coil that powers it.

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