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RWD 19xx-1984 DeVille and Fleetwood,
1985-1996 Fleetwood and Brougham Forum Discussion, 94 fleetwood idle prob. in Past Cadillac Vehicle Discussion; the MAF is in the big cold air tube, and I do know thay he sent out the pcm to ...
  1. #16
    slayu2day's Avatar
    slayu2day is offline Cadillac Owners Member
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    Re: 94 fleetwood idle prob.

    the MAF is in the big cold air tube, and I do know thay he sent out the pcm to be reprogramed for the no pollution control stuff.

  2. #17
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    slayu2day is offline Cadillac Owners Member
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    Re: 94 fleetwood idle prob.

    I will try to find out the tune of the pcm. Probly all that you mentioned. Maybe its this type of chip

    chip.jpg


    this is what autozone sells for my vehicle.

  3. #18
    slayu2day's Avatar
    slayu2day is offline Cadillac Owners Member
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    Re: 94 fleetwood idle prob.

    m1300222_00_68_cat_header.png

    I have something similiar to this , but much bigger in diameter.

  4. #19
    jayoldschool's Avatar
    jayoldschool is online now GM RWD V8 addict
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    Re: 94 fleetwood idle prob.

    Your PCM does not use PROM chips like that. No matter what anyone else tells you.

  5. #20
    slayu2day's Avatar
    slayu2day is offline Cadillac Owners Member
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    Re: 94 fleetwood idle prob.

    Well I'm not sure, thats just what autozone says is for 5.7 94' fleetwood. I will just gut the whole darn thing out and drop a freeking crate engine in it and call it done... LOL All in all its running pretty strong with only this minor issue. I'll get more info soon.

  6. #21
    jayoldschool's Avatar
    jayoldschool is online now GM RWD V8 addict
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    Re: 94 fleetwood idle prob.

    Ok, good luck with the guy from Autozone. I hear those guys know everything.

  7. #22
    slayu2day's Avatar
    slayu2day is offline Cadillac Owners Member
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    Re: 94 fleetwood idle prob.

    He he he for sure, I know how the autozone guys are. They know as much as the computer screen will tell them...LOL . Oh and by the way, I talked to the guy I bought caddy from and he said its the flash inside the PCM . Maybe I need to have the PCM programmed again ? Is there a way I can check the PCM for faults ?

  8. #23
    slayu2day's Avatar
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    Re: 94 fleetwood idle prob.

    Ok, well I'm starting to understand and learn about what the hell this car does have and does not have. Its my 1st 5.7 LT1 , mechanicaly I am fairly good about things, but electronics are just not my thing. All I know is the caddy moves alot faster than it should with just some bolt-ons. I think thats alot to do with the 373 rear-end gears. Other caddy's can't keep up with it, unless they are turbo-charged or something along those lines.

  9. #24
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    turbojimmy is offline Cadillac Owners Connoisseur
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    Re: 94 fleetwood idle prob.

    The gears make a huge difference, particularly off the line.

    The '94-95 LT1 engines are controlled by the Powertrain Control Module (PCM). It's a PROM (Programmable Read Only Memory)-based piece of electronics that manages all of the fuel and timing events for the engine. The PROM (or EPROM - erasable programmable read only memory), as the name implies, is programmable. There are different types of PROMs - early ones are actual chips, later ones are components soldered to a circuit board. With the advent of PROM-based PCMs, auto manufacturers could use the same piece of hardware to control virtually any drivetrain that they manufacture. They "burn" the PROM with information about that vehicle's specific configuration (engine, transmission, weight, axle ration, options, etc) and pop it into the PCM. The PROM is the "chip" you posted a picture of. In the early days, you would get one custom burned for your application. I had a glovebox full of them in my Grand National - one for street 87 octane, one for street 100 octane, one for the track 110 octane, one for the track 114 octane, one for the street 93 octane w/ alcohol, etc. and so on. I would leave the cover off the PCM so I could swap them out easily.

    Eventually I moved to a FAST (http://www.fuelairspark.com/) system in the Grand National which is a lot like modern PCMs - they can be reprogrammed over and over again using a laptop and don't have "chips" in them anymore. If I wanted a specific tune, I would flash the PCM with the laptop - it would take about 15 seconds. Run it down the track, check the logs, make adjustments and upload them to the FAST module. This is a good segue into what our Cadillacs have in the way of PCMs.

    I haven't taken our Cadillac PCMs apart, but based on Jay's response and my own observations, I would assume that our PCMs have EEPROMs in them. EEPROM is defined as Electronically Erasable Programmable Read Only Memory (EEPROM). The EEPROM is soldered to the circuit board and can be electronically erased and reprogrammed over and over again. It makes it even easier for manufacturers to use the same PCM in a wide range of vehicles. They just "flash" it with vehicle-specific information and pop it in. There are "tuners" for just about every vehicle manufacturer these days that will flash your PCM for you in order to increase performance, eliminate emissions checks, etc. There are also DIY software packages that allow you to upload information to the PCM yourself. On my '96, for example, I tuned out the AIR pump check so the SES light would stop coming on once the pump failed. I also changed the temperature at which the fans come on so it ran cooler.

    As an aside, our computers *might* have a CALPAK or MEMCAL chip in them. It is an actual chip that has default, limp-mode fueling information in the event the main computer fails. Not sure when GM stopped using those. I think that's what Autozone is showing you, actually. EDIT: I pried open an extra '96 PCM I have and it does not have any sort of removable chip in it other than the knock sensor module.

    This guy has lots of information on LT1 and LS1 tuning: http://www.lt1pcmtuning.com/

    Back to your issue: you can't really check the PCM for faults. You can send it to a tuner to see what's been changed vs. stock, but in order to do it yourself you'd have to invest in software and cabling. I doubt the PCM has failed. You can have it put back to stock, but if the previous owner has had it reprogrammed to eliminate certain emissions equipment, and has removed that equipment, then you're going to get a Service Engine Soon light when the stock programming looks for that stuff again.

    I think you should be looking beyond the PCM for your issue, particularly if the program you have had been working fine in the past. Something has failed that is causing it to run poorly.

  10. #25
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    Re: 94 fleetwood idle prob.

    Ok, and yea, it has ran fine for the past year, but it only runs with the poor idle issue occasionally, and when its happening it runs perfectly while accellerating. I will keep looking in other areas then.

  11. #26
    jayoldschool's Avatar
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    Re: 94 fleetwood idle prob.

    Start with checking the obvious culprits. Coil, coil wire, grounds, EGR valve.

  12. #27
    slayu2day's Avatar
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    Re: 94 fleetwood idle prob.

    I few pics under my hood at air intake and PCM

    smmotor.jpg
    PCMCDY.jpg

  13. #28
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    Re: 94 fleetwood idle prob.

    Here's the way I did my '96:





    Whoever owned your car created a lot of extra work to tuck that air filter down where it can theoretically get colder air. There's not really any benefit in doing that versus the way mine is pictured. If I were you I'd rearrange it to look something like mine. I can't take the credit for this design, as I've copied many others who have done it before me. The reason I say this is because the MAF is sensitive to vibration and it's resting right on the upper radiator fitting. It can't be good for the radiator or the MAF. Second, you can put the PCM down where it belongs, mounted securely. The air filter will still get plenty of cool air there since that's where the stock air cleaner and associated ducting was.

    I'm not sure what sort of pollution stuff the guy bypassed, but your smog pump and associated plumbing are still there. The pump might have stopped working so he bypassed it, dunno. Have you solved the idle problem yet? If not, I'd see if you can score a stock '94 PCM and pop it in. He may have bypassed checks that could point you in the direction of the problem. For example, it may not be reporting EGR, O2 or MAF issues.

  14. #29
    slayu2day's Avatar
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    Re: 94 fleetwood idle prob.

    Well, I don't know if idle issue is solved, but it has only acted up once since I changed fuel filter. I also found a bad vacum line that I replaced. So, ok for now... probly something to do with missing pollution crap. I will find out what has removed.

  15. #30
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    Re: 94 fleetwood idle prob.

    Hey guys, its been awhile. Well, I just wanted you to know my Caddy is still on and off with my issue. The problem would come up just not as often. Recently, when it starts doing its thing with low idle and dying out , but the low idle symptom now is "lurching" when eihter in gear with foot on brake, or in park. Like someone has a dimmer switch connected to my idle and is turning the dial up and down. But, when that happens, I go under hood and manually rev the throttle a few quick high revs, and it seems to come out of it.
    Also, does anyone elses throttle pedal tension loosen up after getting on it ? It will stay that way for a short while then it will go back to "normal" tension. The throttle cable goes from pedal to a unit on drivers side fender wall, then continues on to the motor. It has always done this, I just though something to do with the mods because it only does this after getting on the motor. The reason I bring this up is recently its not been loosing up as much as it used to. And since it seems to fix my idling and lurching issue after just a few fast and quick manual revs from under hood, maybe theres a connection between the two. ? Any thoughts. guys ?

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