Engine/Transmission (1998.5 - 2002) IAT sensor (cleaned )

[Alan Reagan]

I changed out the IAT with the new one from the dealer. Before installing them both, I did four temp tests for readings.



Old

30* 30. 1K

76* 9K

81* 8K

130* 5. 57K



New

30* 40K

76* 13K

81* 6. 87K

130* 4K



Some noticeable differences. Bad news is, my emissions light is on. I've got to check the connector this afternoon. A torrential downpour started as I was finishing up and my 6 year old needed some immediate "thunder" attention. When I cranked up this morning, the yellow light was on. May end up with the old IAT back in there to see if the light goes out. What do you think, Marco? The new one looked in range but check the difference at 30*.

 

[Marco]

Hi Alan,

Sorry to hear about your trouble with the light. I guess you need to check the connector.



Your old sensor does the same thing mine did.

At low temps it's resistance is lower than it should be, thus it tells the ECM higher temps.

At higher temps it reads higher than it should be, thus telling the ECM that the air is colder than it actually is.

Down your mileage goes!



You should see a good mileage increase with the new sensor!

Please report the EGT's and MPG with the new sensor.

Marco

P. S. If you don't mind, how much did you pay for the sensor over there?

 

[Alan Reagan]

Eighteen bucks and change. I think it listed for 21 or 22 but they gave me a discount. At least it's not the check engine light. I just walked out and checked the connection. Looks good. I'll go over everything this afternoon. If I can't find it, I'll take it to the dealer and see what they say. It's a real PITA to do those measurements. Had to keep the sensors over a cold cup of ice to get the cold readings. The resistance changes pretty quickly, as you might guess.

 

[Marco]

At least that thing is cheap.

I'd bet you've disconnected some wire while you were working on it.

Have you noticed a difference in the response of the New/Old sensor. My old sensor would change it's reading much slower than the new one.

I've used my freezer to check the cold readings. Brrrrrrrrrr...

Marco.

 

[Alan Reagan]

I did notice a difference. The engine sounded quieter and spooled up faster. Also, there has been a surge in acceleration usually noticeable in 3rd that I noticed had smoothed out. Thinking about it, that's about the time the sensor is going to be changing values as the air heats up from being compressed. I'll post if I see any difference in mpg. I doubt I will since I'm already pretty good in that area. Concerns be about the connector though. Just out of curiousity, will the battery have to be disconnected before the light will extinguish?

 

[Marco]

Alan,

Disconnecting the batterys will extinguish the light only if the problem that has set that light is no longer there.



You could also simply try to pull the fuse # 3 in the PDC. ( 12v for the ECM)



Marco

 

[Alan Reagan]

OK, I get the Dufus award for this little experiment (check engine light). The stupid thing is, I must have turned the key on to let up the windows before I connected the harness on installation of the new IAT. That's what set the fault. Duhhh. Anyway, EGT at idle is running about 50* (264 versus 314 (I have digital gauges)) cooler. That's the difference I was hoping/looking for. EGT at idle had been creeping up to the point where I had to idle a loooong time before shutdown. Thanks, Marco and Bowhunter. The dealer ordered me a new IAT for the old one after some testing. Now I have a spare.

 

[Marco]

Alan,

I've been waiting to hear how your trouble with the little light would have been solved. Sounds like that lil' sensor can cause big trouble!



Glad to hear everything is fine now!



Did you notice the EGT's drop while driving at steady speed also?

Let us know about your mileage.

Marco

 

[Alan Reagan]

I drove a 140 mile round trip yesterday afternoon and noticed that the EGT's were about 100* lower. With the old IAT at 70 I was showing 650* on flat roads. Yesterday, I was showing 550* when the wind wasn't blowing and 600* bucking a headwing on the return 70 miles. So I've seen a drop. I let you know again in a few days/weeks if this is consistent.

 

[Marco]

Alan,

with a EGT drop like you're reporting, I'm more than convinced that you'll get better mileage too!

 

[JR2]

Well Dads (Jack in Alaska) egts are lower after cleaning the sensor (as noted in earlier post) and now he has checked his mileage. It is up about to 18. 9 from about 16-17 (on the highway). The only other changes he made during that time were fuel filter/air filter and oil.



I replaced my IAT sensor with a new one ($28 from Dodge), but really did not have time to do much driving before I had to leave town for a few weeks for work. Inital results looked good, idling in neutral egt about the same, idle in drive EGT down 100-130 deg. The truck does not seem to emit as much smoke with the PE and EZ on. I did not have a chance to make a long trip to check crusing EGT or milage, I will report on those later.



I will also test my old sensor when I get a chance... .

 

[DennyDay]

Alan: Mine was loose like yours. When I pulled it out the '0' ring didn't even have any marks on it, but the sensor looked like it had been used for an oil pan plug! At 87k+ miles I guess it's allright. I'll test it (by drive) tomorrow, and pick a new one up at the dealer.

Question: Does the MAP sensor go into the same passage in the engine, and should it be cleaned also?

Thanks for posting this, i never would have given it a thought, but was tired of the increased smoke.

Denny

 

[Steven]

$28 for the IAT ??

Where are you guys getting the IAT for under $30. My local 5 star rolleyes dodge parts department wants $49 !!!

 

[Marco]

JR2 so you're saying that mileage went up about 2 MPG? Not bad for having cleaned the IAT! What would you gain if you changed the sensor?



Steven, I've payed my new one about 25 bucks here in Italy. It came directly from the States. I think your dealer is a "little" pricey!



I've seen so many people posting here complaining about things that I think are IAT related. Consider that the emissions are way too high with a bad IAT. I've taken several readings with the old and the new sensor. NOx are about 50% higher with the old sensor.....

Starting the truck cold, NOx with the old sensor gives 1100 ppm and stays there as the engine warms up.

With the new one 700ppm and decreasing rapidly at engine warm up. After 40 seconds the NOx is down to 400-450 ppm.





Hmmmmmmmm, is it time for a recall for that sensor?

Hello Big Brother, are you reading this?



Thanks for your attention.

Marco.

 

[Alan Reagan]

Steven, I paid $18 and change at the dealer. Want me to send you one? Marco, Whas up? Sounds like C. D. Day was probably loosing some boost like me with the loose IAT. Jury is still out. I believe my day to day commute mileage has improved about . 3. The computer (whcih is pretty accurate on my truck) has made it to 21. 2 which is up for my daily commute mileage. I haven't changed anything else so I either got a good tank of fuel of the IAT change is helping. There is definitely less smoke on these hot Georgia days. I get a puff on gear change and that's it.

 

[Marco]

Alan,

The other day I went to a guy that lives near to me. I've BOMBed his CTD some time back. He has a bad IAT too. Since I've done several CTD's here, I've decided to call all those guys and tell them to check their sensors...



Try to keep in mind your findings and read through the TDR MSG's.

You'll see a lot of people complaining about things that are most probably IAT related. It's the same on Fritz's site, Pickup Truck.com... .



Marco

 

[Alan Reagan]

A month ago I would have thought it was crazy but now I think that's a pretty accurate statement. Thanks again for all the research you put into this.

 

[Marco]

Thanks for your understanding Alan.



My point is, I've bought a truck ( Which I've payed good money for) that has several problems from the begining. The brakes are poor at best. The schoks also. The lift pump... and now the IAT!



If I add up all the fuel I've waisted due to the bad IAT sensor!



AAAAAAAAAAAAARRRRRRRRRRRGH, can't they build a truck that does not need to be fixed by his owner?

Marco

 

[Marco]

I've forgotten to mention!



I would have NEVER been able to trace the problem down to the IAT sensor without the help of Andy and Doug!



A big thanks MUST go to the ADT gang!



Marco

 

[yogibear]

Intake Air Temp. Senspr

Just called parts dept. at my dlr. , with my discount, $16. 00. Some of you are getting ripped off!! Nothing new tho, heh.

Larry