LM7 Will not warm up

**Tony1** · 09-30-2021, 10:12 AM

Okay new to this so don't burn me out of the gate.
I tried to do homework but I'm obviously missing something. Have had an lm7 built for my sons 2001 Suburban with a very minor cam so not to require any computer changes. I keep getting po128 codes which leads to a po300 code and cannot get the temperature above 154 degrees at highway speeds. The car has been setup for towing in the desert.
It has an all aluminum three row radiator and a oil cooler add-on Factory like the 2500 series 6 liters.
P.S. I have put three thermostats in it including a factory ACDelco.
So please any help guidance or direction would be greatly appreciated.

**Cutlass** · 10-03-2021, 02:53 PM

Maybe a bad engine coolant temp sensor?
99 times out of 100 its a thermostat problem but you have tried that.
Only other suggestion I have is to have a tuner turn that code off.

**Tony1** · 10-04-2021, 08:36 AM

I've actually already replaced the temp sensor as well and Trace the wiring all the way back to the ECM.
This weekend I changed out to a different style thermostat from the factory one and now I'm running at a 216° . I think the real problem is is the factory thermostat opens up entirely too quick and a slightly shorter thermostat in the same temperature range may do the trick I'll post back on how that works out the current thermostat is $195° one from jegs but it's a much shorter thermostat and it made a major difference in the temperature.

**Tony1** · 10-16-2021, 11:41 AM

This weekend I replaced the thermostat again with 180 degree thermostat from NAPA it is a part #109 now the temp runs in the 160s at cruise and 205 at idle. Is this close enough? I don't know yet at a cruise temp of 154 I would get misfire code of P0300. with the Jegs tstat it would make 216 but no codes. The 216 seems too hot to me. Any help or thoughts would be appreciated.

**Cutlass** · 10-16-2021, 04:50 PM

Originally Posted by Tony1

This weekend I replaced the thermostat again with 180 degree thermostat from NAPA it is a part #109 now the temp runs in the 160s at cruise and 205 at idle. Is this close enough? I don't know yet at a cruise temp of 154 I would get misfire code of P0300. with the Jegs tstat it would make 216 but no codes. The 216 seems too hot to me. Any help or thoughts would be appreciated.

216 is definitely not too hot. 160 is too cold at cruise for this code.
You need to run the correct temperature or you need to find a tuner guy/company to change the computer so the temperature does not matter.

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