Was messing around with the live data function on my code reader tonight. The first thing I noticed is that my IAT sensor readings were rather high. I read between 147 and 168 degrees. My cold air snorkel is in place, and I have no large holes in my air intake system. Seeing as my coolant temps registered as only 177 degrees at the time, this seemed rather high. Do our intake manifolds really heat soak that badly, or might I have a bad IAT sensor? I've owned intercooled turbocharged cars running 28psi that had lower IATs in Manhattan traffic.

The next thing I noticed was error code P0171 (System Too Lean). This is a new one, which I believe started just after I changed out my water pump and coolant temp sensor. Since then, it seems like my engine never gets up to the 195 degree thermostat rating. The good news is that it does not seem to be the temp sensor malfunctioning. Many times, the coolant is cool enough to dip my finger into comfortably.

I know this is usually a vacuum leak issue, and will go looking for sure, but first wanted to see if maybe there was a proprietary issue usually responsible for this problem. I have erased this code more than once, and it keeps coming back, so it is not just arecord of a previous issue.

Thanks for any help.

 

No, this is usually an issue with the thermostat sticking open.

 

I was referring to the P0171, not the coolant temp.

 

Can be a vacuum leak or even an exhaust leak. Or even just a bad O2 sensor

Your coolant temp is to low.

Your intake tempature reading is taken from the manifold not to far above the cylinder head so yes that is reading correctly. If you want it to read cooler readings look into the thread link in my signature on the Switchable IAT mod. I have not tested it this summer but last fall noticed 40 degree temp difference between the OEM sensor location and my new sensors location in the air filter housing snorkel tube.

 

I read your previous post

https://dodgeforum.com/forum/dodge-r...ater-pump.html

and I was immediately concerned. 140F, even 177F is too low. It might sound good on paper but excessively low running temperature results in dramatically accelerated engine wear and higher emissions.

I also drill a 1/8" hole in the thermostat if one is not present. However in this case, with the info you have provided, I think either too much water is bypassing the thermostat or the thermostat was bad or mismarked out of the box. This has happened to me!

As to your IAT temperatures, yes, mine are very high and I do think it is a problem. When the IAT sees high incoming air temp, it leans the fuel mixure and naturally then loses power. This vehicle clearly suffers from extreme underhood temperature issues. I have commented on this issue in various threads but have yet to resolve it. MobileAutoRepair has suggested a switchable IAT mod that he says works for him, and it should help. I was working on something related but got sidetracked.

 

Had a thought: I don't wish to insult you but this (low temperature) can also result from the thermostat being installed backwards. It happens..

 

When I installed the thermostat, I did drill a 1/8" hole, as I always do, in the thermostat's plate. The thermostat was definitely installed right side up as well. I don't think my hose modification caused the problem, because the internal diameter was dead on with the stock piece, and the fittings' internal diameter is smaller than the hose ID anyway. Gotta be something going on with the thermostat.

When I have the chance, I am going to get the doghouse off, pull out all of the diagnostic tools and do a full workup. Van's had a lot of hard miles these past couple of months, and it might be time to just give it a full checkup.

I am going to just have to pull out the thermostat, check its operation, and see what I get.

I am working on a solution for the underhood temps, and something for high IAT's as well. If it works, I will have pictures and all this week. If it doesn't work, I'm going to keep it to myself and never say anything at all.

Also, at idle, with my foot off of the throttle, should I be seeing 13.2% throttle on the readout?

 

Agreed. I always begin with the last change and work backwards. There's no way it's the bypass hose so something is up with that thermostat. As I said in a previous post I have installed brand new thermostats that were bad (or pehaps miscalibrated) right out of the box.

 

Today I installed my IAT solution and will post a new thread with the details , assuming it works

Adding an electric fan does solve hot soak issues and will prolong the life of my wiring and my PCM. I'm very glad I did this mod! But when stuck in heavy traffic underhood temperatures do still get very high. I have considered adding louvers to the hood or adding a hood scoop but this will let in rain water. Soaking the PCM seems like a bad plan..

 

The P0171 went away on its own, for whatever reason, and I am about to hit the thermostat and basic tuneup.