IAT accuracy crucial?

Soooo, truck running crappy. I assumed it was due to exhaust leak at front pipe in proximity to the upstream 02 sensor. I finally have a nice sealed exhaust and it does run better but not quite right, and I’m anal about it. I notice the smaller things. Lol, anyway I was cruising around in my not quite right truck (stumbles a smidge) with my scanner running to check it out. I looked down and noticed (for the first time) that the IAT was reading 120 degrees. Bouncing around. It’s 70 here. This leads me to believe the MAF is screwed up. It dropped to 88 at one point. If you were me, and ain’t got money falling out of ass, would you replace it? How important is the temp in relation to fuel mixes? Could this be my angst?The trims are around 0 and 3-5 and seem pretty stable. Thank you.

 

Ps, the timing was wicked advanced too, don’t have a screenshot though... like 20 degrees advanced. Thanks again

 

Hmm I don't have any advice other than to say 120˚ IAT when it's only 70˚ outside does sound way too high. I get IATs in the 120s sometimes in the summer when it's triple digits out, but never when its in the 70s.

Have you tried cleaning the MAF using MAF cleaner? Easy to do and cheap. No check engine light codes?

 

I did clean it, and no codes. I just ordered a OEM Denso for 27 bucks on EBay. I remember buying the one that’s in there from AutoZone for well over a hundred bucks a year or so ago. The Denso looks remarkably different than the Autozone one. The one that’s in there is square and the filaments are kinda hidden and hard to get to. The Denso is way different. Hopefully this is what is supposed to be in there.

 

Hopefully someone wicked smart stumbles apon this. Seems to me the trims would be out to lunch...

 

Yeah you only want to use Denso sensors on these trucks, Toyota builds them around the exact specs and parameters of Denso sensors so aftermarket ones can be very hit or miss (usually miss).

The only thing I find concerning about that purchase is how cheap it is...eBay is notorious for selling 'fake' Chinese sensors that are made to look like OEM ones but really aren't. If you have any trouble after you install that thing I would be sure to take it out. Save the old one just in case.

 

Yeah your fuel trims are fine if they are within 10 degrees on either side of zero. 3 - 5 for your average long term trims is normal.

Hows your coolant temp, is it around 190˚?

 

Yeah, 186... everything else looks ok, the little evap icon is blinking red on the system overview page but no codes

 

True, I thought the same so I bought the most expensive one. Every Denso on EBay regardless of seller is right around the same price. The Denso number is the same for nearly every Toyota in that yr range.

 

Only one way to find out lol, at least MAF sensors are easy to swap out so if it turns out to be no good you can just put the old one back in until you are able to source another.

As for the high IAT though, I don't know... Maybe @Speedytech7 can shine some light on why it's so high when the ambient temps are low.

 

Not just high, nearly 50 degrees, occasionally anyway. I’m curious what the computer does with the temp information... thanks again

 

Warmer air, especially 50 degrees warmer, would be a lot less dense so the truck would need to correct fuel trims because of this.

 

I would agree but the trims look normal.

 

yeah i dont think 120 degree air would push it out of spec. Air temps can get that high sometimes down here in florida, i was just saying that's why the truck would need to know the IAT.

 

Wait, if it thinks the temp is bouncing around it would deliver a fuel mixture based on that temp but the air is actually a different density I imagine it would run roughly. Especially when it’s changing so frequently. I think. Omg I got a headache. Regardless, new maf it is. I guess I was just hoping for reassurance . I hate it when it runs crappy

 

I think you're on to something. Temperature is an important factor in calculating the mass of the air flowing into the engine, which informs how much fuel it should inject.

I'm guessing if it reads a higher temp than actual, it'll think it's getting less air than it is, and so I think it would be backing off fuel, and running lean.

But, the computer is more complicated than that, especially since it can read the results at the o2 sensor.



Sooooo....

 

Yeah, I was hoping someone smahtah than me would come across this. There is a well written thread regarding all this stuff but it doesn’t get into the IAT, he actually posted a formula for determining maf performance but I had enough problems w/ algebra, never mind astrophysics

 

PV=nRT


It's just algebra

 

I aint wicked smaht or nothin, but before you go throwing money at it that you might not need to.. read the IAT after you've been driving at speed for like 5-10 minutes.

Occasionally Ill monitor the IAT on my 2nd gen via a ScanGauge and there is a huge spike when the truck is standing still (heat soak from the engine bay)

I can see you're not moving when you took that screen shot in your first post, so you might want to confirm that the 120 reading inst artificially high due to limited air flow through the engine bay before buying new parts

 

Looks like pervert to me. Good night