Hey guys, having a little trouble with my 83 hurst olds. Car is stock, retaining the original ccc 307 equipment (minus air pump and cat). Car ran great when i rebuilt the engine 2 years ago and slowly started rough running. Its been sitting and the threads for the fuel inlet were leaking so i sent the carb out to be rebuilt and rethreaded. Got it back and installed it, car runs rough, idle is very rich and the car shakes like it has a decent cam in it. I scanned the ECM with my snap on scanner, and my results were mixed. At first i was having a problem communicating with the ecm, then the data stream would show odd results, high tps, lean o2's, a 50 * dwell reading, then would drop out to low tps readings, 500 o2 reading, 14* dwell, all while running the same. Then all the readings went to N/A. Ive used this scanner on this car before with no problems and customers cars with ccc so i know the scanner is working right. If i unplug the MC solenoid the car runs better. Since the computer is special order, does this sound like a computer failure? Ive also checked all grounds as well, no issue there. Any ideas would be awesome. Thanks!
possible computer issue? 83 hurst
- Thread starter Joeyg329
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Did you tune the carb after you put it on or just put it on straight out of the box from the rebuilder?
Were the well plugs re-epoxied?
Sounds like the MC Solinoid was not properly installed to the right height, you may want to get the proper adjustment tools and fix.
Also doesn't hurt to install a new TPS and MC Solinoid and do the proper adjustments with a voltmeter on the TPS and intall the MC Solinoid to the right idle height.
Sounds like the MC Solinoid was not properly installed to the right height, you may want to get the proper adjustment tools and fix.
Also doesn't hurt to install a new TPS and MC Solinoid and do the proper adjustments with a voltmeter on the TPS and intall the MC Solinoid to the right idle height.
Thanks for the reply! The carb guy replaced the MC solenoid and the tps, i measured tps and it was .46 at idle. I have not checked the MC dwell, the carb guy stated he tuned the carb to factory specs. All wells are epoxied. I adjusted the idle screws as well and it idled a bit better when i turned the screws out about a turn. Whats puzzling me is the inconsistent data stream readings. The RPM will say 0, 475, and vary while the car is idling at 900 in park. The tps reading can go from zero to 1.0 just watching the datastream. Ive even seen -2.9 in/hg for a map reading haha. O2 voltage freezes. Just seems like a bad computer and hopefully not some kind of ground problem 😢 I havent scanned the car since i got it running 2 years ago (everything read fine at that time) so im not sure when the readings started going haywire. Whats the proper method for checking dwell with a multimeter? Once again thanks for the help!
You can check dwell with a multimeter by hooking up to the green one wire connector near the carb, with the meter set to a 6 volt scale.
I would check a few more things before condemning the ECM. Disconnect the scanner and with key on engine off, is the check engine light lit? It should be. When you turn the key on do you hear the MC solenoid ticking at first? You should. Jump out terminal A and B on the ALDL connector and turn the key on. Are you able to flash a code 12? You should be able to do so, this is a normal code with the engine off. Any other codes flashing?
With the scanner disconnected, start the car and check your dwell with the multimeter. I would run the car at high idle and once warmed up, you should see dwell at 30 or so. If you create a vacuum leak, does dwell go down? If you choke off air flow to the carb, does dwell go up? These are all signs that your ECM is working. Another way to test this is to disconnect the MC solenoid at the carb, which should send the carb full rich. Then ground the dwell connector (green terminal) which will drive the MC solenoid full lean when you hook it back up. With engine running at 2500-3000 RPM connect the MC solenoid and see if the RPM changes significantly. By running disconnected you are full rich, and by connecting with the terminal grounded you are going to full lean. If the ECM and the MC solenoid are working correctly, you should see a drop in RPM as you go lean. This test is listed in the 87 manual as a System Performance Check.
Try creating a code and see if the ECM responds. With engine at idle, depress the TPS plunger manually for at least 15 seconds and see if you can set a code 21 for TPS. Disconnect the vacuum signal from your MAP/VAC sensor at idle and see if that sets a code. If you are getting codes it would again indicate that the ECM is functioning.
You mentioned the car was rich when it acted up, how do you know it was rich? You may have a problem with timing advance. When the car is in base time, it can sometimes seem to run rough and will idle low. Have you checked your timing? If so, are you sure you did so correctly, by either jumping pins A and B on the ALDL or disconnecting the under hood 4 wire distributor connector? Another simple test is check idle speed with engine running normally, then again with with A and B jumped. You should see a significant drop in RPM because you are now in base time. If this happens it is just another indicator that the ECM is functioning.
Regarding the scanner problem, when does the scanner act up? Key on engine off, only when engine is running? Does the scanner act normal once you disconnect the MC solenoid?
You mentioned that you checked grounds, I would make sure you test a loaded circuit by checking grounds with key on engine off and then again with engine running. Also I would check power to the ECM, make sure you are getting battery voltage. I think it is a pink/black wire in 87, not sure about 83. Again test this under load with key on engine off and then with engine running.
Any of the solenoids on the car could damage the ECM if they are shorted, MC, EGR, AIR valve. Is your ECM 1225450? Your PROM may be unique to the VIN 9 motor, but according to Rockauto.com, that ECM is used in all 1982-1983 full size and G-body Buicks and Oldsmobiles. These should be really easy to find and even with a VIN Y PROM you car should still run fine.
Hope this helps.
I would check a few more things before condemning the ECM. Disconnect the scanner and with key on engine off, is the check engine light lit? It should be. When you turn the key on do you hear the MC solenoid ticking at first? You should. Jump out terminal A and B on the ALDL connector and turn the key on. Are you able to flash a code 12? You should be able to do so, this is a normal code with the engine off. Any other codes flashing?
With the scanner disconnected, start the car and check your dwell with the multimeter. I would run the car at high idle and once warmed up, you should see dwell at 30 or so. If you create a vacuum leak, does dwell go down? If you choke off air flow to the carb, does dwell go up? These are all signs that your ECM is working. Another way to test this is to disconnect the MC solenoid at the carb, which should send the carb full rich. Then ground the dwell connector (green terminal) which will drive the MC solenoid full lean when you hook it back up. With engine running at 2500-3000 RPM connect the MC solenoid and see if the RPM changes significantly. By running disconnected you are full rich, and by connecting with the terminal grounded you are going to full lean. If the ECM and the MC solenoid are working correctly, you should see a drop in RPM as you go lean. This test is listed in the 87 manual as a System Performance Check.
Try creating a code and see if the ECM responds. With engine at idle, depress the TPS plunger manually for at least 15 seconds and see if you can set a code 21 for TPS. Disconnect the vacuum signal from your MAP/VAC sensor at idle and see if that sets a code. If you are getting codes it would again indicate that the ECM is functioning.
You mentioned the car was rich when it acted up, how do you know it was rich? You may have a problem with timing advance. When the car is in base time, it can sometimes seem to run rough and will idle low. Have you checked your timing? If so, are you sure you did so correctly, by either jumping pins A and B on the ALDL or disconnecting the under hood 4 wire distributor connector? Another simple test is check idle speed with engine running normally, then again with with A and B jumped. You should see a significant drop in RPM because you are now in base time. If this happens it is just another indicator that the ECM is functioning.
Regarding the scanner problem, when does the scanner act up? Key on engine off, only when engine is running? Does the scanner act normal once you disconnect the MC solenoid?
You mentioned that you checked grounds, I would make sure you test a loaded circuit by checking grounds with key on engine off and then again with engine running. Also I would check power to the ECM, make sure you are getting battery voltage. I think it is a pink/black wire in 87, not sure about 83. Again test this under load with key on engine off and then with engine running.
Any of the solenoids on the car could damage the ECM if they are shorted, MC, EGR, AIR valve. Is your ECM 1225450? Your PROM may be unique to the VIN 9 motor, but according to Rockauto.com, that ECM is used in all 1982-1983 full size and G-body Buicks and Oldsmobiles. These should be really easy to find and even with a VIN Y PROM you car should still run fine.
Hope this helps.
Hey!
Checked dwell, 30 at idle warmed up. dwell is unresponsive to change and randomly jumps but i can get a consistent reading of 30 sometimes.
Jumping the A and B on ALDL connector does not flash light, it stays on steady (light does come on koeo).
Depressing plunger doesnt throw a tps code, and the tps is no longer getting a 5 volt signal.
I have also disconnected MC solenoid and checked resistance, it was in spec of the what ALLDATA stated. Ive disconnected the egr solenoid as well, tested good, with both unplugged ECM signals were still all over the place.
As far as timing, its set to spec with the connector grounded. It does change idle when i ground timing connector out to base timing.
The reason i mention running rich is that the exhaust stinks, burns eyes, and has a dark smoke to it.
With the scanner readings can be all over the place regardless if car is running or just key on. I use my scanner daily so im hoping my scanner is working correct haha.
My ECM is 1225450 as well.
Sorry i know thats alot of scattered info haha. Thanks again for the input!
Checked dwell, 30 at idle warmed up. dwell is unresponsive to change and randomly jumps but i can get a consistent reading of 30 sometimes.
Jumping the A and B on ALDL connector does not flash light, it stays on steady (light does come on koeo).
Depressing plunger doesnt throw a tps code, and the tps is no longer getting a 5 volt signal.
I have also disconnected MC solenoid and checked resistance, it was in spec of the what ALLDATA stated. Ive disconnected the egr solenoid as well, tested good, with both unplugged ECM signals were still all over the place.
As far as timing, its set to spec with the connector grounded. It does change idle when i ground timing connector out to base timing.
The reason i mention running rich is that the exhaust stinks, burns eyes, and has a dark smoke to it.
With the scanner readings can be all over the place regardless if car is running or just key on. I use my scanner daily so im hoping my scanner is working correct haha.
My ECM is 1225450 as well.
Sorry i know thats alot of scattered info haha. Thanks again for the input!
So you jumped a and B, turned key on, engine off, and the light did not flash at all, not code 12 or anything? That is not a good sign for the ECM. Also, you held down the TPS plunger with the car running at idle for at least 15 seconds and did not set a code? Also not a good sign for the ECM. The ECM appears to be controlling timing, but fuel control seems erratic.
The 87 manual says anything under 10ohms on the MC solenoid is bad, and that 20-32 is normal. Think about other solenoids like anti diesel on the carb or an idle solenoid, a canister/purge solenoid, AIR solenoids, etc. The 5 volt reference signal is controlled by the ECM as well, so if that is low, that also is not a good sign for the ECM. Low battery voltage or a poor ground to the ECM could cause all of this I think.
I think you are on the right path by checking all solenoids, powers, and grounds. If everything checks out you might need to try another ECM. The 87 manual says that anytime a solenoid tests bad, replace the ECM as well. It is possible your old MC solenoid was bad but you will never know for sure.
The 87 manual says anything under 10ohms on the MC solenoid is bad, and that 20-32 is normal. Think about other solenoids like anti diesel on the carb or an idle solenoid, a canister/purge solenoid, AIR solenoids, etc. The 5 volt reference signal is controlled by the ECM as well, so if that is low, that also is not a good sign for the ECM. Low battery voltage or a poor ground to the ECM could cause all of this I think.
I think you are on the right path by checking all solenoids, powers, and grounds. If everything checks out you might need to try another ECM. The 87 manual says that anytime a solenoid tests bad, replace the ECM as well. It is possible your old MC solenoid was bad but you will never know for sure.
I've also heard bad ignition modules can cause a timing issue as well and lead you to think it's the ECM but that looks not to be the case here...
Test the sensors and jump the A and B terminals and that should tell you if the ECM is toast.
Test the sensors and jump the A and B terminals and that should tell you if the ECM is toast.
Yeah no flash at all with a and b terminals jumped. The only other connection on the carb besides the tps and mc solenoid is the 1 wire ac compensation solenoid. 83's seem to have less electrical devices then the newer cars.
As of today, the car no longer runs. . . it barely starts, dumps fuel, check engine light is on with no communication with a scanner and cant even rev up. So its in push mode haha. I ordered a reman ECM from ebay for 45.00, it will be here monday, so until then the hurst will sit in the shop. Ill post my results on monday or tuesday when i get it in! Thanks again guys for all the input!
As of today, the car no longer runs. . . it barely starts, dumps fuel, check engine light is on with no communication with a scanner and cant even rev up. So its in push mode haha. I ordered a reman ECM from ebay for 45.00, it will be here monday, so until then the hurst will sit in the shop. Ill post my results on monday or tuesday when i get it in! Thanks again guys for all the input!
ECM fixed it! Still wouldnt start, tried cleaning the spark plugs but they were too far fouled, replaced them and the car fired up, made a few adjustments and she runs great. Thanks again for all the help! Now if my window felts will show up she will be ready to cruise with the rest of my fleet. 
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