I've been chasing poor mileage problems on the wife's V70 GLT for ages now. To date I've worked through CEL for front 02 sensor, replaced. Spent months working on vacuum lines including the entire oil separator/flame trap system. Virtually every soft line and elbow has been changed. Highway mileage is about 22, but city is only "up" to about 15. Recently changed the ECT as it was slightly out of spec, but no code. I have a known good MAF coming too, just in case.

Recently someone suggested the IAT (intake air temp sensor), but the info I'm digging up here and on the web is anything but clear, including one thread that seems to think the IAT is the airbox thermostat (which I don't have). The IAT seems to be present or not depending on manufacture date. There are so many posts about where it is located, intercooler plumbing, intake snorkel, under the airbox, in the airbox, on the core support; I have not been able to find it regardless. The cabin temp sensor in the air guide seems to be fine. There are posts saying this is the only one, and that the injection does or does not use it, and others saying there is a second sensor on the passenger side with a blue connector. This car is "late", in that it has the later style belt tensioner, but I don't know about late as far as injection, or if that truly matters.

Can anyone clarify? I can see that an intake temp sensor thinking the charge is very cold would make the car run rich. My reading has always indicated that the MAF in this car is more of a temp sensor than anything else. Isn't that the case? One post says no, the MAF does not have an IAT. Others say it IS the IAT.

Thanks,
DS