View Full Version : '90 SC Running Cold/kiw MPG

05-22-2018, 10:03 PM
As you guys might remember, about a year ago I replaced my entire AC system, and my cooling fan motor. Ever since then, the engine has been running really cold, especially when the AC is on. I think this is causing the car to run rich, and my MPG hasn't been the same ever since (I've been averaging MAYBE 16mpg on Shell V-Power 93). I don't have a lead foot, and I don't really send it into boost very often, so this MPG really is weird. It really only gets up to temp after like 20 minutes running with the AC off (no cooling fan running). But when I'm running the car with AC on (cooling fan on), it never really gets above the "N" on the gauge. I know my new AC condenser is ALOT thinner than stock (providing better airflow). I think maybe this is confusing the computer, messing up my air/fuel ratio. Am I worried over nothing, or is this an actual problem I need to deal with? I still need to do a full tune up on it and hopefully that will improve MPG, but I figured I'd run this past you guys beforehand.

Edit: Typo in the title, meant to say low MPG

05-22-2018, 11:19 PM
Sounds like you might need a thermostat.

05-23-2018, 07:55 AM
Also, there's a TSB on the sending units failing causing them to read LOW.

I'd check the thermostat housing and the radiator with a non-contact thermometer and see how hot they're actually getting.