Overheating problem possible ECM?

[Hrtbeat1]

Help!!!

I developed an overheating problem. I found the water pump had a bad rear seal and replaced it. While I was at it I replaced the timing chain and gears. Every thing is dead on timing wise. I took the radiator out and gave it some much needed TLC, cleaned and straightened all the fins, and did a thorough check of the cooling system. All looked good. I decided to go with a 160 degree thermostat and fan switch sensor. After installing these the car started fine but the fans never kicked on and once the thermostat opened the temp gauge pegged. I tried going back to the original setup and now the temp gauge hovers near 225 or so. I can get one fan to kick in with the AC on but not the other. Both fans spin when grounding the "A" and "B" terminals of the ALCL conector in diagonistic mode. Both fan relays have also been replaced and swapped.

I guess my question is Do you have to modify the EPROM to take advantage of a lower Thermostat/Fan Switch? Or is there a chance that my ECM is faulty?

By the way this is a 90 L98 Auto 110K compression all cylinders 195 (#7) to 210 (#1,2,4) with #3,5,6,8 in the 200-205 range.

Thanks for any help or advise. Magmotor you out there?

 

[EricVonHa]

There is probably air in the cooling system. It sounds as if all of your troubleshooting and replacing of parts should yield a highly efficient cooling effect. Double check your levels, and if it seems a little low, squeeze the upper and lower hoses as you fill up the system.. this will cause the air to move around as you displace it by filling the system. You may also have a bleed screw on the thermostat housing...

 

[Hrtbeat1]

System "burped" very well, no air there. Still doesn't answer the fans kicking in. BTW no bleeder @ the thermostat. Thanks for the help though.

One of the reasons I suspect the ECM is now I get a code 42 (electronic spark timing), before changing the timing chain I didn't get this. This sugests an ignition module, I have tried an "OEM" and and Accell and both produce the same results.

Maybe the cam is worn and I need to adjust the valves .....

 

[EricVonHa]

From what I remember of the HEI system and the EST circuit is that the ECM sends a 5 volt signal through that brown wire near your wiper motor (the one you disconnect to set base timing) upon startup to operate in "base" timing. If the wire is left disconnected... it may set the code.

 

[Ken]

Do you have to modify the EPROM to take advantage of a lower Thermostat/Fan Switch?

No, you do not have to reprogram your computer or anything for that matter.

Or is there a chance that my ECM is faulty?

It's possible, but unlikely. My guess is that it's electrical in nature though. :confused

 

[Hrtbeat1]

correct you are EricVonHa. I do believe it is a 5VDc signal, as far as leaving the connector disconnected and getting the code, I am unsure. It is on the checklist when I am working on timing, just so I don't miss it.

That's what I thought Ken. A thermostat is just that ... it opens at a set value. I could see the fan switch not working due to the computer ... but to have neither fan working unless with the AC on ... yes the AC does trigger the EPROM to turn on the secondary fan ..... wait I may have figured out my problem. Well maybe I was getting ahead of myself.

I do agree it has to be something electrical ....

 

[Magmotor]

Check your PM.

 

[vettenick]

Your eprom was programmed with the assumption that the engine's using a 195 thermostat. Using a 160 would cause the system to stay in open loop. That means running richer for no good reason. If the car is stock and you want the car to run right, keep the 195 in there. The car will run better. If you're modifying things and a lower thermostat is called for, then do it. But the eprom will have to be programmed. If you don't believe me, have someone hook a scanner up. I'll bet it takes forever to go into closed loop. And if you experience cold weather, below 40 degrees, then you'll really have a driveability problem.
I don't like the running hot situation. Are you sure that you have the correct thermostat? Was it installed correctly. And is it even opening at all?
I can fax you a code 42 troubleshooting chart if you want. Just email your fax #to me. Good luck.