[Nissan4Life]

Well I know for sure there's no fuel leaks. I did all the basic tuneup stuff... Plugs, wires, injectors, Air filter, fuel filter, seafoam, converters, MAF, etc. but I imagine there's still work to be done. My dryrotted intake hoses for one. I know the main hose into the manifold has a few large cuts in it. And the entire EGR system has been blocked off. Plus the truck idles around 2k on startup and stays until put in gear and driven for a couple minutes. I guess I'll start there next.

If both your pipes pre and post the MAF have leaks in it, tHat is unmetered and added air. That will wreck havoc on your air/fuel mix and thus your MPG. If nothing else duct tape those hoses/pipes.

 

[Nissan4Life]

I agree with you on the air/fuel mixture being thrown out of whack. I'm also wondering now if it's only idling high on initial start up due to the air temperature. I'm sure I read somewhere that there's a sensor that monitors air temp and factors that in. The smaller hoses are wrapped in electrical tape at the clamp points due to rot and tearing. The main hose is so tightly compressed between the manifold and airbox that I can't hear any air being sucked in through the cracks. Obviously this isn't an ignorant attempt at ruling them out of the equation. Just me fooling myself into believing it's not an emediate priority (been restoring this truck for a while). They're definitely high on the list for this month. And while I'm not overly clueless on the intake system in general I am very much a noob when it comes to the ECU, so all of this is good info. I appreciate it.

I'll contact a few dealerships today for the factory hoses and update on any status changes.

I believe that the mass air flow sensor on these trucks are of the heated wire variety. Thus colder denser air is compensated for. Your truck should go into "cold start enrichment" right when you start it with the higher RPM as a result. This is based on a coolant temp sensor. When the coolant temp is warm your car should idle back to normal. In some cases this temp sensor is faulty and the car stays in cold start mode. This will defiantly eat your MPGs, cause low power and pollute like a MFer. You might be able to test this if you get the resistance (ohm) spec for specific temps. However testing at the sensor might not give the reading which the ECU reads. The connection might have corrosion (green death) and will increase the resistance. Reading at the ECU pins is the best place. Or just remove the sensor and clean the tip as well as the connector.

 

[Nissan4Life]

Don't know how my Frontier does it as it is new enough I hardly work on it (as far as engine stuff). But on my 300zx there are 2 temp sensors. The 2 wire unit is for the ECU. There is another single wire unit that is for the gauge. If this convention holds true for newer nissans, the 2 wire temp sensor you have is for the ECU. Just check the parts. It is still like this. 2 temp sensors, one for the ecu the other for the gauge.