Mk3 Thermostate Question

btwilson86 · 06-14-2007, 04:43 AM

I've read that running with no thermostat will cause your ECU to run in an open loop, giving incorrect A/F mixtures and ignoring some of the sensors (such as MAF, IAT, etc.) until the car (finally) reaches it's proper operating temperature. This is because the computer thinks it's alot cooler than it is (since the engine takes so long to warm up)... In any case, it's worse for emissions (if that matters) and is very likely to cause premature wear on your engine. I wouldn't recommend it. Found out the hard way that it's bad (destroyed the cold start system on my 92 Jetta)

06-14-2007, 04:43 AM	#7
btwilson86 Super Moderator Join Date: May 2007 Location: Billings, Montana Posts: 1,034	I've read that running with no thermostat will cause your ECU to run in an open loop, giving incorrect A/F mixtures and ignoring some of the sensors (such as MAF, IAT, etc.) until the car (finally) reaches it's proper operating temperature. This is because the computer thinks it's alot cooler than it is (since the engine takes so long to warm up)... In any case, it's worse for emissions (if that matters) and is very likely to cause premature wear on your engine. I wouldn't recommend it. Found out the hard way that it's bad (destroyed the cold start system on my 92 Jetta) __________________ 1989 7MGTE R154 Targa Top White Package w/Blue Interior Driftmotion 57trim CT26, Upgraded Intercooler, 2.25" Hard Pipes, 3" Turbo Back Exhaust with Test Pipe, HKS VPC w/GM 3 bar MAP sensor, APEXi S-AFC, Walbro 255lph fuel pump, ProSport EVO Series Boost / Fuel Pressure / AFR gauges, Lotek a Pillar Gauge Pod, HKS Type 0 Turbo Timer, Eibach Lowering Springs, Tokico Illumina II TEMS struts, custom powder coated Motegi Racing TrakLite wheels