Kind of a pain, but can the ECT be tested in water like a thermostat? I’m not sure it can, but it would help determine if that 15 code was a wiring issue or not. I tend to believe you must have a wiring issue.

However, if the ECT was faulty, would it cause problems during Open Loop operation? I thought the ECM ignored the O2, Knock Sensor, and ECT when the engine was cold and allowed the distributor and EST to run the engine until it warmed up? If that were the case, the engine would run okay while cold, even with a bad ECT. Anyone know for sure? I am still learning here.

At some point, you may have to allow the possibility you have a fault in your ECM computer. I understand that it is rare, but since it is a reman from Cardone and you don’t know if it ever ran right, it may be the problem. I ran an ECM with a bad PROM in it and the car ran terribly. I changed to the correct CDR PROM and the car runs great now.

 

I don't know what an ECT is, but a code15 is for a bad CTS sensor on a 82/84 CF. Usually if bad, you will have lots of fuel dumping into the motor than normal when cold, but it can go the other way as well. If you have teflon tape wrapped around the sensor that will wig out the reading as well since it takes its ground through the threads/body to the motor. Teflon tape is a no no for those type of sensors, use high performance thread seal if you must.

You can read the sensor in ambient temp to see if it reads close to that. If so, and then installing it back in the motor it reads very low or higher than normal it's not the sensor it's your coolant. Yes, you heard right, the coolant. The reason is that your radiator is grounded somewhere and electrolysis is going on and creating to much voltage in your cooling system and wigging out the CTS sensor. This IS a thing believe it or not and I just helped a guy with that issue recently. I think he thought I was crazy, but that was the issue and it fixed his CTS problem. One thing you can also do is measure the voltage by one lead into the coolant and the other to ground and read what it is. If you have much of anything, it is too high and you must completely flush the system, heads, motor and radiator and find where the radiator is grounded which is usually around the rubber pads area.

This is just one of those odd tips that I have come across on these cars over the last 30+ years. However, it you could still have issues with wiring as well and or a bad ECM. GL

 

I assume he is defining the ECT as “Engine Coolant Temp” sensor. I stand corrected on the terminology. Formally, the Coolant Temp Sensor is correct. One thing we must do with these CFI’s is speak the same language or we are building a Tower of Babel!!!

Also, in an earlier post, he said he had changed to the newer style, two wire CTS. Does the new one get its ground via the block also?

 

My mistake, the CTS is the item I have been referring to. The sensor that sends a signal to the ECM so it knows the engine coolant temperature.
Yes, the car runs very rich when it is cold or warmed up. Smell of gas in the garage is very pungent and there is black soot on the floor below the muffler outlets.
Per the SM the Code15 is voltage too high or an open circuit. I'm going to perform a test on the circuit with my PowerProbe and a voltmeter at the other end just to make sure the wires are not shorted to ground. This will not tell me if the ECM internal circuit is bad, but at least I can check the harness from sensor to firewall connection (the big plug behind the heater relay) and then from firewall connector to ECM harness connector. I will not do this test with the line connected to the ECM of course, don't want to fry it....

Per the circuit diagram the CTS is grounded to the same circuit via a splice as another line (TPS). Wondering why it just doesn't ground to the ground plug that is connected to the front of the intake manifold. Why not ground it closer to the sensor?
I did not put any teflon tape on the sensor before the install. It had sealant on it out of the box.

It has just occurred to me that I can pull the plug off the sensor and put a voltmeter on the yellow signal wire to see if I am getting any voltage at all, wonder if I will get this with just the key on or does the engine have to be in operation. Supposed to be 5vdc signal from the ECM.

 

Was researching the C3/C4 ECM change.. and found this info:

NOTE: If you do manage to use a 1984 computer module from a manual transmission Corvette in a 1982 Corvette without reprogramming the EPROM Chip, you will get a problem with a very high idle RPM.

Uh oh.. I wonder....

 

That is correct. Check Posts 6 and 10. We tried that. He checked his ECM and it is a reman 1982 ECM of the correct code. Still could be an ECM problem, but he does not have another to swap.

 

The 82 originally had the one wire CTS and grounded to the engine. The 84 had the two wire and requires to wired in to match our 82’s.

Either Bucaneer or L46Man will have to help you check your CTs wiring to make sure it is wired in correctly. You could also just change back to the original one-wire type and eliminate that possibility.

I’m just spit balling here.

 

Has anyone heard of the company Dynamic EFI? I heard that they can modify an ECM from a 1988 or so corvette to fit to and run a 1982 corvette. The ECM in my 1982 corvette is bad and I am looking for answers on how to get it running good again.

Thanks!

 

Dynamic EFI EBL Flash II IS a great solution for ANY CFI car that has a bad ECM and you cant find another one and want to keep the CF system. They have been around for a long time and I have been using their ECM for more than a dozen years or so with no issues, it is very reliable. Their ECM IS laptop tunable, therefore, you need to tune it which isn't that hard really and lots of people on this forum to help you out and on Thirdgen.org where the owner of Dynamic EFI is a MOD there along with other great tuners.

Read down through this link and pay special attention when you get to the NOTES towards the bottom. I also have the stock 82 corvette tune for a starter BIN which is about 98% good to go, Plug-N-Play if you will. GL with your search.
CFI ECM 82/84 corvette

 

Thanks for your help!

 

Bucanneer, Thanks for your advice. The new Dynamic EFI is in. The check engine light is on and throwing a code 23 for an Air Temp Sensor. But I am told this code is non-existent for my 1982. Any ideas?

The car is running pretty well with the new unit in but the mechanic cannot get the laptop to connect to the ecm to tune it. Could getting rid of that code be part of tuning the vehicle?

 

Get a IAT relocation kit for the 85-97 corvette and mount it into the air cleaner base. Connections are to C12 and A11. Adding a wide band O2 would be recommended to. This is if you cut off the ECM harness connectors and splice on the pin style connectors. Not sure it will work if you used the ham board.

 

Well glad to hear that it is running, but I have an answer and a question below.

OK, the 82 does not have an IAT sensor and you don't need one to tune your 82, but you can install one if you like. An IAT makes it a "little" easier to tune, but with the tune I gave you for a stock 82, you really do not need to install an IAT sensor. To turn OFF or disable the IAT function in the tune do this...

1. go into TunerPro and look in the Flags/Switches box area on the left side of the screen
2. scroll down to the Malf Flags - 12 thru 24 - Bit 1 - IAT23
3. double click on it and ensure you do not have the "Set" checked, if you do, uncheck it and Save.
4. go down a little further in the Malf Flags and find Malf Flags - 25 thru 42 - Bit 7 - IAT25
5. double click on it and ensure you do not have the "Set" checked, if you do, uncheck it and Save.
6. After you Save the tune in TunerPro, load that tune file into WUD and upload the tune into the ECM.
7. Your CEL should not come ON due to an IAT false malfunction, but you will see a flashing IAT Malfunction Code in WUD diagnostic table still which you do not have to worry about since you disabled it in the TunerPro file and does not effect the tune in any way.

Not sure what you mean by... "the mechanic cannot get the laptop to connect to the ecm to tune it." If you are talking about connecting to ECM via What's Up Display (WUD), you MUST set the Comm port first so that Windows can talk with the ECM. You DO NOT manually tune the ECM using WUD. WUD is for uploading the tune files in any bank you choice, Data Logging, Malfunction Code reporting, Sensor and all other input monitoring. However, it also can do LEARN mode and be updated within WUD. TunerPro is the tune editor to actually make manual changes to your tune in various tables etc... You DO NOT need to connect to the ECM using TunerPro, ONLY WUD connects directly to the ECM.

My question would be if your mechanic can not connect to the ECM, how did he load the tune file I sent to you into the ECM in the first place and how is your motor even running? That tune file I sent you is about 98% done and you DO NOT need a WB O2 sensor either to finish it if you want to do that, but you can install a WB if you so desire and it WILL work just fine with the HAM board and is connected to the ECM. Since I do not sell the EBL or really do tech support for that product, I would contact Bob at Dynamic EFI. He IS very good at his EBL and tuning as well and can answer any question about it that you may have. He is also very good at getting back to the customer and is a all around nice guy to talk with. I would email him from his site email and ask him for a number to call so you can talk with him since I do not think his number is posted on his site anymore. I hope this helps you out.

 

Very helpful. I will show this to the mechanic. Thank you very much. I may even load the software on my laptop and call Bob myself. Have a Happy New Year

 

You have been very helpful thank you! I might even download the software onto my laptop and call Bob myself.

Have a Happy New Year!

 

Well, thank you and hope you can get it squared away soon. Calling Bob is a great idea, tell him Tom from AZ said hello.