Engine runs cold
#21
Ok , here are the codes that came up . 15,21,22,23,44,45, and 51 . He wanted to replace the ECU and the PROM .
#22
im having same issue, any ideas yet?
and did you properly change the gaskets on the tstats
and did you properly change the gaskets on the tstats
#23
The problem is the OEM routing of your heater core lines, they go back to the radiator instead of the water pump (see attachment #1 previous post, look below the radiator cap).
When you rev your engine the water pump circulates a ton of coolant and in doing so it sucks a bunch of cold fluid in from the radiator, causing instant temperature drop in the heads and intake. Not as dramatic once you have been running at temperature for a while, but that can take forever in the winter
The fix is to get a water pump hose barb nipple (napa,etc..) and then splice/plug the heater core return line where it goes into your radiator. Caveat is your engine will sometimes run a bit warmer than T-stat because of the restriction at the T-stat, but it's never been a serious problem for me and I run a vortec-tbi with custom tune that sometimes yields very high EGTs during long hill climbs. Maybe 210*-215* max in summer time (measured by CTS using ALDL cable & tunerpro)
BTW, Junkyard tbi ECM's are DIRT CHEAP and are usually fine (99%). Any 7747 from '87-'92 in a half ton chevy with your powertrain will work (350/700r4 was very common). Everybody should have a spare or 2...
When you rev your engine the water pump circulates a ton of coolant and in doing so it sucks a bunch of cold fluid in from the radiator, causing instant temperature drop in the heads and intake. Not as dramatic once you have been running at temperature for a while, but that can take forever in the winter
The fix is to get a water pump hose barb nipple (napa,etc..) and then splice/plug the heater core return line where it goes into your radiator. Caveat is your engine will sometimes run a bit warmer than T-stat because of the restriction at the T-stat, but it's never been a serious problem for me and I run a vortec-tbi with custom tune that sometimes yields very high EGTs during long hill climbs. Maybe 210*-215* max in summer time (measured by CTS using ALDL cable & tunerpro)
BTW, Junkyard tbi ECM's are DIRT CHEAP and are usually fine (99%). Any 7747 from '87-'92 in a half ton chevy with your powertrain will work (350/700r4 was very common). Everybody should have a spare or 2...
Last edited by helo; 01-23-2012 at 10:13 AM.
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