cruiser54

Or go to the JY and get one. Or, clean the one you've got......

DFlintstone

Finally someone! I'd thought after years here someone might help me out! Zero, a bit fat Goose EGG! Here is. (was), my thread on IAT resistance. >>https://www.cherokeeforum.com/f2/iat...stance-140073/

I don't notice problems with 225 Ohms in always above freezing temps.

Edit. OK hat's of to one response, (or two if you count the decimal off) Black states a 5.5. and Suppera a 540. So those are likely real numbers one might expect. (my thanks to you two)

cruiser54

You live in Kommiefornia where the temps don't vary alot.

DFlintstone

For me, it's frustrating than on one of the best Jeep teck forums, only one plausibly realistic IAC reading was posted. (although, I will buy the 5.4 as 540 ohms).

I get it! (that nothing remotely matches the chart). I Just wanted to know what is "normal". Btw if we had the "designed" resistance, ya'll mounting in (presumably cooler) , plastic could compare your readings.

Sorry of I'm getten' to "tekky" here in tech. Fuel is my biggest expense. Just unplug it if you don't care.

Btw, thank you Cruiser for learning me up on a bunch of this!

67 GMC

I'm not sure where this thread is headed...Readings in the intake manifold will be higher than in the plastic tube or air box. I would think the ECU would most likely be set up for making adjustments to fuel/air using the stock location. Don't see how moving would make it better as it would make it think it was cooler more dense air than it really was.


You can fry an egg on the manifold as it is directly above the exhaust manifold so I'm sure the engineers knew it would always be warm and just wanted to know the temperature of the air immediately before the combustion chamber and make the fuel injector pulse adjustments with that in mind.


I could be wrong - just thinking it through. Actual results may vary.

cruiser54

Move it to the air cleaner and never look back.

DFlintstone

My though exactly. Iz's just wanting numbers to compare with, as no-one in their right mind would expect them to match the numbers on the (shared) ECT chart. Pete's DRB tells him it's 80 something in AZ. (mounted in plastic)

Still, 2-1/2 is almost a consensus. If I go 550-650, , Suppera posts 540, and Black's 5.4 can reasonably called 540.

I did a pretty flaky job taping in two resistors I had that read 225, (in parallel), eliminated it and haven't looked back.

So Lerob. Can you duplicate what you posted? Also, does the backfire go away if you just leave it unplugged?

SuperRA

yea, that's what Dflinstone and I were discussing in his thread. Did the Renix engineers take the hot manifold etc. into account or not? Does the radiant heat in the manifold affect the sensor's reading? Does this do that and that do this blah blah..

Cruiser says to just move it, and who am I to question him. But no my conscience says I must question it. Why? WHY? LOL.

Anyways, maybe when I have time and after I fix a bunch of other more pressing issues, I'll mess with resistors or sensor locations

cruiser54

They run better when located in the air box. No loss of MPG.
Don't need to be mounted in metal.

It's not a super big player in the grand scheme of things like a MAP sensor.....

DFlintstone

I had come to the same conclusion. (actually with the same words!) Early fuel injection sometimes had an extra injector for "cold enrichment" I suspicious the IAT MIGHT serve a similar function. If you had a block heater, the ECT sensor won't tell the ECU it's -10* out there! In that case something needs to send a "heads up!" to the ECU. Heck, it might not do squat until the resistance goes over 3,500 ohms...(about 20*F). Mine seemed fine on the few 32* mornings I had last season, (with the 225 ohm resistor). That said, someday while I'm already at the JY I'll probably pick up a replacement IAT. Mine, I believe a wire broke from flexing right where it comes out of the sensor. I could probably solder to the "stub" if I tried.

cruiser54

Please don't solder your stub....

DFlintstone

Oh, but now I need to....with 18 pics and a U-Tube vid!

If I'd have known the flexing there where the wires come out it the IAT would break the copper within, I'd have put a dab of silicone there 12 years ago!

67 GMC

Definitely a poor design but it's lasted 25 years so can't fault it too much. I agree with Cruiser though- Don't solder your stub-can't be healthy

leorob

DFlintstone, if I understand your question, I haven't tried it with the iat disconnected, I will. I ordered a GM iat it will be here mon/tues when I get it installed I'll let you know results and if it works the part #. A shop I talked to says that the iat isn't used by ecu until temp sensor says engine is up to temp, if true then my resistor should work. Cold start was no different than before resistor was installed, but weather is really nice now.

DFlintstone

Know what? that GM guy may well have an excellent point. I'm working now but later I'll take a peek in the Renix fuel injection manual. In "open loop" it only uses a few crucial sensors, then the manual tells you which are added in "closed loop" after it warms a bit.