1989 Chevy Celebrity Recent ECM but still have issues.

MELEN01

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1989 CHEVROLET CELEBRITY

Computer problem
1989 Chevy Celebrity 6 cyl Front Wheel Drive Automatic Station Wagon 193000 miles

I have changed my ECM and the car is running much better but still have a few problems. 1- The fuse gets very hot and sometimes blows. 2- The speedometer has gone crazy, I'm going at 25 mph and it registers 65 mph. It started working as soon as I changed the ECM 3- The transmission suddenly seams to shift radically from one gear to another every once in a while. WOW! I'm going to go CRAZY with all these issues. I just put it in today, July 3, and was told that I would have to run the car for a while until the ECM "learns" and receives new data from the sensors. I was also told that it could be the "map-sensor" so PLEASE HELP ME. What's going wrong. One other thing, the EMC is not connected to the diagnostic plug so I can not perform a scan, WOW! Please help me. Thanks

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MMPRINCE4000

MECHANIC
8,549 POSTS

The diagnostic plug should connect to the existing harness. Once all the plugs have been connected to the new ECM the diagnostic terminal is one of these plugs.
You may have the wrong ECM or have it connected wrong.
Does your SES light illuminate when ign. Is on?

While true the ECM will need a few hundred miles to re-learn sensor parameters, this is also true if you disconnect the battery.
Did you use the old PROM chip from the previous ECM.
The issue with the speedometer may also be ECM related. The speed sensor puts out pulses per mile which the ECM converts to MPH.

Is this a 3 or 4 speed auto? The 3 speed is controlled by a cable, while the 4 speed is vacuum controlled.

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Friday, July 4th, 2008 AT 6:49 AM

MELEN01

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Thanks. I will do that and check to see that the plug that feeds the diagnostic terminal is connected correctly. Can you help me with the fuse blowing every once in a while? And why is the car shifting from one gear to another every once in awhile? When I used the car today it seems to be doing better but I would really appreciate your help on this issue. Thank You for your time and most valued service. Hope to hear from you SOON. If you like you can call me at 1-787-733-8324 collect and that will be of great help. You can call after 6:00 pm est. Time. Again thanks a lot. The truth is that I am unemployed at this moment and have to do repairs on my own so PLEASE HELP ME.

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Friday, July 4th, 2008 AT 4:43 PM

MMPRINCE4000

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If this is a 3 speed auto, shifting is controlled by a TV (throttle valve) cable connected to the throttle body cam. The cable may be out of adjustment or kinked.
Pull on the cable and make sure it moves smoothly and requires greater tension the farther it is extended.
The 4 speed is controlled by vacuum, so look for a vacuum leak at connector on tranny. Also inspect the shift cable.
If you cannot find anything wrong, take it to a trans. Shop that will give you a free inspection and diagnosis.
This may give you some idea of the problem.

The fuse issue, make sure the fuse is of correct amperage, DO NOT put a larger amp. Fuse in place of the old one.
The fuse is blowing because the circuit is drawing more current that designed. What fuse is it? The ECM fuse? If so recheck the connections to the ECM, they usually only fit one way, make sure none of the pins in the connector or ECM are bent. Always disconnect - battery when working on ECM.

If the MAP sensor was bad, the car would barely run and would run very rich, since the ECM would set a default value to the MAP sensor. This value would be WOT (Wide Open Throttle).

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Saturday, July 5th, 2008 AT 6:24 AM

MELEN01

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HELLO! And thanks for your advice. You are correct about the ECM fuse and I will check that all pins are just right. If the plugs are good and pins okay then, what can be blowing the fuse? GOT YOU ON THE "MAP SENSOR" ISSUE, THANKS. One other issue. When I run the car I can be going at 25 mph and the speedometer has 65 or 70 mph. What can that be? About running "rich', I assume that you mean the air and gas mixture. That was going on until I changed the ECM and now it is consuming MUCH less gas. And the car idles kind of rough and jittery so I think that it might be a sensor that has to do with the idle control. One?, When you say "throttle body" concerning trans do you mean on the motor? Or is their one on the trans? I'm not a car tech so that's why I ask. I REALLY appreciate your help and you don't know how thankful I am FOR YOU TAKING THE TIME TO HELP ME. Hope to hear from you soon. Than You so very much, George from sunny PUERTO RICO.

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Saturday, July 5th, 2008 AT 9:45 PM

MMPRINCE4000

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The best thing to do is to scan the ECM with a scan tool, or have someone do it to find out if the MAP sensor is the problem. So first priority is to get the diagnostic plug hooked up.
If your SES light is working and you connect the diagnostic plug, you can use a paperclip to short terminals A and B of the diagnostic terminal. Turn ign. On, the SES light will flash code 12 (flash, pause, flash, flash) three times. Then it will display error codes, when all error codes are displayed it will return to code 12.
The idle is controlled by the IAC (Idle Air Control) valve, which can fail or get dirty, do not remove the IAC when in diagnostic mode on ECM (A&B shorted) or with engine on or ign on.
The issue with the speedometer could be the sender is bad, or not compatible with the ECM or a shorted wire connector to the sender, it could also be the gauge in the IP.

The throttle body is the air intake on the intake manifold, connected to the throttle pedal.

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Sunday, July 6th, 2008 AT 7:30 AM

MELEN01

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Hi Prince! Thanks again for your help. WOW! Have I resolved a bunch of issues with your help. Trans is three speed and it's fixed. THANKS. Concerning the ECM it is the right one and I double checked with "Auto Zone" where I purchased it and it's the correct one. And the idle problem was what you said and I have replaced the sensor and the car fells MUCH BETTER. THANKS AGAIN. As soon as I get into the other issues I will let you know. THANKS A MILLION FOR YOUR ADVICE. George from SUNNY PUERTO RICO. PS, what is the SES light. Don't forget, I am not a tech like you so PLEASE be more specific, THANKS AGAIN>

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Sunday, July 6th, 2008 AT 7:04 PM

MMPRINCE4000

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SES is Service Engine Soon light. Some call it check engine light.

When the ECM finds a sensor out of specified range e.G. The Coolant temp sensor, it will set the SES light and store an error code. The SES light will stay on all the time until the sensor is fixed.

The diagnostic port is called the ALDL or Assembly Line Diagnostic Link.

Other sensors:
MAP Manifold Absolute Pressure
TPS Throttle Position Sensor
CLT Coolant Temp. Sensor
O2 Oxygen sensor

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Monday, July 7th, 2008 AT 5:46 AM

MELEN01

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HELLO again MR. Prince! You have been of GREAT help. I really appreciate your advice and, believe me, it has been very useful. I have a friend that has a scanner, OBD 1, and he is going to help me. He is a student at a technical school (auto) so he just might be able to put his recent acquired knowledge to the test. We will see. I just remembered, the trans is a 4 gear shift and not a 3 as I mentioned before but that is all ready been solved. It was a vacuum line, just as you stated. WOW! I don't know how to thank you for your most VALUABLE SERVICE. I have to say that "CARPROS" is the best and with members like you, like what else can I say! Well, I think that you know what I mean. Again, THANKS A MILLION. Just hope you accept checks. That's a joke. I really appreciate all the time you have taken to help me. George from SUNNY PUERTO RICO.

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Monday, July 7th, 2008 AT 4:12 PM

MELEN01

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Hello Mr. Prince. I've got to tell you that I did what you advised me and the car is FIXED. I jumped the A and B with a clip, just like you said, and the Coolant sensor was out and so was the MAP. Put in the new ones and the car is just PERFECT. WOW! What a relief. Now the car is running just fine. Thanks to your generous advice and knowledge. I also later discovered that the plug that feeds the socket for the scanner was not properly hooked up so now that issue is also solved. Now the car runs great and it is consuming much less gas. It was a gas guzzler for quit a long time. Nice and smooth, that's how the car is so THANK YOU again for your valuable advice. Hope to hear from you soon. George from SUNNY PUERTO RICO. PS. Concerning my tech student friend, well I guess he learned a thing or two with your help. One other thing. I noticed that the car doesn't have a Cat-Converter. How can that effect the cars performance? Hope to hear from you SOON. Thanks. George From sunny Puerto Rico.

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Friday, July 18th, 2008 AT 10:53 PM

MMPRINCE4000

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Replace the convertor. The car is designed to run with a convertor which reduces NOX and hydrocarbon emmissions.

It is against Federal law to remove the convertor and while it may not hurt performance, it should be installed.

Many times, people will remove the convertor because they are bad and somewhat expensive depending on your car.

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Saturday, September 6th, 2008 AT 6:43 AM