1988 brougham TPS and MAP sensor problems
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RWD 19xx-1984 DeVille and Fleetwood,
1985-1996 Fleetwood and Brougham Forum Discussion, 1988 brougham TPS and MAP sensor problems in Past Cadillac Vehicle Discussion; Hi Y'all..I haven't been on these forums in quite a few years. Some of you "old timers" may remember me ...
  1. #1
    Angela Desmond is offline Cadillac Owners Fanatic
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    1988 brougham TPS and MAP sensor problems

    Hi Y'all..I haven't been on these forums in quite a few years. Some of you "old timers" may remember me building the hot rod 425's and 472's.But now a'days my hubby acquired a 1988 Brougham with the 5 liter carburated engine and I have constant problems with TPS switchs and MAP sensors. We buy'em and within a few hundred miles the codes start coming up that they went bad. We purchased them from NAPA, not a dealership and they run in the $50 range.Anybody out there have problems like this? If so, whats the solution 'cause, me personally, I'm ready to put a match to this car...Funny thing is that even though the "check engine" light comes on and those are the codes, the engine isn't running badly, yet...I appriciate any help someone can give me...

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    SafariOne is offline Cadillac Owners Fanatic
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    Re: 1988 brougham TPS and MAP sensor problems

    That is definately odd. These parts generally run for years trouble free. Are you certain it is not grounding issues and not the parts?? Have you done any voltage tests on the parts that come out when bad?? Have you checked the manifold ports for fouling up etc.?? Hope you find a sloution.

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    katter281 is offline Cadillac Owners Member
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    Re: 1988 brougham TPS and MAP sensor problems

    I was actually going to suggest the same thing. I had a problem where I was burning up distributor ignition modules and I traced it back to a bad ground. Usually when electronics like that continually go out it's usually due to a connection issue...a short, bad ground, or broken wire.

    I'd check the resistance of your grounds and see if they're too high. Are you familiar with the procedure?

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    Angela Desmond is offline Cadillac Owners Fanatic
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    Re: 1988 brougham TPS and MAP sensor problems

    Thanks for the timely replies guys! No I'm not familiar with those procedures. I rarely had to even work on a car that runs off a computer as we have a 73 and a 70 with 472's in them. We have checked the TPS switches with a voltmeter to see if they go from 1 to 5 volts while opening the throttle to see if the switch was bad and it always was. Never did any checks on the MAP sensor; just depended on the computer codes saying it was bad. If it's not too much trouble, could you explain these procedures to me?..Thanks

  6. #5
    katter281 is offline Cadillac Owners Member
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    Re: 1988 brougham TPS and MAP sensor problems

    These are pretty quick and painless tests. The first thing I would do is test the resistance of the ground wire on the TPS sensor. You should be able to put one probe on the TPS ground wire, and the other on a known good ground. If you get more than say, 50 Ohms I'd say that's suspect..

    You can also test your grounds for excessive resistance by using a digital multimeter. Switch it to ohms and use the probes to test across your ground straps. You should also test the battery negative terminal to ground. If any of these connections look corroded or dirty, that could contribute to high resistance.

    You can also try a voltage drop test to check for excessive resistance in circuits under load. Since it sounds like these sensors are dying while the car is running, you might try testing the charging circuit for excessive resistance. Instead of re-inventing the wheel I'm going quote someone else's procedure:


    CHECKING THE CHARGING CIRCUIT

    To check the alternator connections on the positive side for excessive resistance:

    A. Set DVM on 2 volt DC scale.

    B. Connect the meter positive lead to the alternator output stud (B+ terminal).

    C. Connect the meter negative lead to the positive (+) battery post.

    D. With the engine running at 1,800 to 2,000 rpm with all lights and accessories on (except the rear electric defroster), check the voltage drop reading. It should be 0.5 volts or less. If higher, the connections between the alternator output stud and battery need to be cleaned. Also, look for loose connections or undersized cables.

    To check the alternator connections on the negative side for excessive resistance:

    A. Set DVM on 2 volt DC scale.

    B. Connect meter negative lead to alternator case.

    C. Connect meter positive lead to battery negative (-) post.

    D. With engine running at 1,800 to 2,000 rpm with all lights and accessories on (except rear defogger), check the voltage drop reading. On the negative side, it should be 0.2 volts or less. If excessive, the connections need cleaning or the negative cable needs to be replaced. Some alternators are mounted in rubber bushings and have a separate ground strap. If so equipped, be sure to check the voltage drop across this strap, too.

    http://www.aa1car.com/library/voltage_drop_testing.htm


    If you end up giving any of these a shot let us know what you get, and good luck!

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    Angela Desmond is offline Cadillac Owners Fanatic
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    Re: 1988 brougham TPS and MAP sensor problems

    thanks for the info...may take me a few days to get to it as I have no garage and its raining like mad here. I will get back with my results ASAP

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    katter281 is offline Cadillac Owners Member
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    Re: 1988 brougham TPS and MAP sensor problems

    No worries! I'm curious to see if you find any funky voltages/resistance values. I'll keep checking back.

    Good luck!

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    Angela Desmond is offline Cadillac Owners Fanatic
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    Re: 1988 brougham TPS and MAP sensor problems

    Funny you should mention electrical problems as a cause. The "check engine" light usually comes on at a red light in drive. Yesterday I drove about 30 miles round trip and at the few red lights I hit I threw it in neutral and kept the revs up a little higher than idle. The light never once came on. Could be making the alt. put out a few more amps than when its under a load idling in drive...

  10. #9
    Angela Desmond is offline Cadillac Owners Fanatic
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    Re: 1988 brougham TPS and MAP sensor problems

    hey Katter..sorry it took a year to get back to you but we finally got around to that '88 and without going through all the resistance tests we found that it WAS a low voltage or amperage problem.. We had a bad sqweel and changed the alternator. That wasn't the squeel (it was the power steering pump) but the alt. must have been bad because the windows go up much faster and the TPS code doesn't come on at all anymore. It only came on at idle, when the alt. is spinning the slowest and now it's fine...Thanks for the tests as I may (I hope not) need them in the future. Personally, I'll stick with my old 472's. I have a nice relationship with them..Hot rodded a 425 years ago and it's still sitting on the stand but planning on dropping it into the '73 Calaise...Probably have to add xylene to the gas ( 11:1 comp.) but I'll live with it.....thanks again

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