writtmeyer

'77 911s 2.7 is suddenly very slow to warm up, after driving 45 minutes still not up to 170 and car misses and stumbles. once up to temp it runs fine. I thought previously that the warm up regulator was not functioning but this behavior became erratic, some mornings fine others missing badly etc. until reaching temp. The cold start valve appears ok as it starts and runs fine for the first 5 minutes or so. Not sure where to go or in what order: temp sensor, thermostat, WUR, other? Appreciate some advice.

Bill Gregory

You know, can't say I've heard of this often, however, if a thermostat is stuck open it can take forever to warm up. You should be able to check your thermostats to see if they are working as it warms up, both on the engine-mounted cooler and the foward loop cooler (I think that's what you have). Temps should get to roughly 170-180, which is pretty warm, before routing oil to the coolers. If you find the engine-mounted cooler getting warm before that, and/or warming oil passing to the front cooler before it's 170-180, either of those could be responsible for a long warm up period. If one of the thermostats is stuck open, my money would be on the engine-mounted thermostat. If the engine-mounted thermostat is bad, you can change it with contortions from the right rear wheel well or possibly easier with a partial engine drop (procedure on tech.rennlist.com).