Bad Mileage and IAT - Please Read!

[Marco]

I got several mails with questions about the IAT sensor.

Seems that several people think that they will increase their mileage by simply swapping out their IAT sensor...

STOP!!!

You will see an mileage increase only if your stock sensor IS bad. If your sensor is good you will gain NOTHING!

I think that you should worry about the IAT sensor if you're one of those that get 14/15 MPG. If you get already better MPG than I think it's useless to change that sensor.

To answer several questions at one time, the IAT sensor can be ordered through DC. The part# for my '99 is 05014197AA. I don't know for the other year models. Cost is about $20 US.

Here's the link for more informations:
http://smokindiesel.com/Technical.htm
Hope this helps.
Marco

 

[Marco]

It's hard to tell for sure but yours are the numbers that I was getting. Except for the fact that my truck is a '99 and has 3. 54's in the back, your's is pretty similar to mine.
What EGT's do you get at idle in "D"?
At 60 mph? 80mph?
Marco

 

[24V-DSL]

Marco... . I'll get these EGT numbers soon. Thanks.

 

[24V-DSL]

Marco... .

I'm getting 14. 5 to 14. 9 mpg from tank one through 7K miles. See sig. for details.

I don't tow and always run empty. 70% hwy, 30% city driving. I'm fairly aggressive, but not a lot of redline visits.

Do you think I should consider the IAT?

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White 2001. 5 2500 ST, SWB, 4X4,QC, AUTO, 4. 10's, LSD, 285/75/16 On Weld Outbacks, PIAA 510's, Line-x, Tinted glass, Redline 85+, Blow-by-bye, RE-0880 & 25-0880,muffler fell off,level truck with 2" tuff country kit, Bilsteins at the corners, Di Pricol egt and boost, Mag-hytec "original flavor" transmission pan and Dana 70 diff. cover, Westin Step Bars,DTT TC/VB,yeee-ha,EZ, Custom Plate 24V-DSL

 

[24V-DSL]

Marco... .

Pre-turbo readings at sea level, 70 degree day:

Idle in D = 400 degrees

60mph. = 600 degrees/8lbs. boost

80 mph = 800 degrees/18 lbs. boost

WOT = 1000-1100 degrees

3" exhaust - no muffler, but still have resonator.

Any input greatly appreciated... .

Joe

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White 2001. 5 2500 ST, SWB, 4X4,QC, AUTO, 4. 10's, LSD, 285/75/16 On Weld Outbacks, PIAA 510's, Line-x, Tinted glass, Redline 85+, Blow-by-bye, RE-0880 & 25-0880,muffler fell off,level truck with 2" tuff country kit, Bilsteins at the corners, Di Pricol egt and boost, Mag-hytec "original flavor" transmission pan and Dana 70 diff. cover, Westin Step Bars,DTT TC/VB,yeee-ha,EZ, Custom Plate 24V-DSL

 

[Marco]

Your EGT's doesn't sound too high.
I had 450 in drive at idle. I get now 350-375...

Take the IAT sensor out and check it's resistance.

At 32°F it should read 30k to 36K ohm
At 77°F 9k to 11k
At 122°F 3k to 4K
At 167°F 1350 to 1500 ohm
at 212°F 600 to 675 ohm

Heat it and cool it( I put mine also in a cooler). The readings have to change quickly when you change the temperature.

Marco.

 

[Marco]

Another thought.
I've seen several people saying that their grid heather would cycle on/off even with a hot engine during the winter. The grid heather is cycled based upon the IAT reading... .
Could be that also that behaviour is due to a bad IAT sensor.
Marco

 

[pwr2tow]

Marco,
I was thinking the same thing about the heater grid cycle. My truck will cycle in the summer in 60 degree temps with a hot engine. My fuel mileage is low especially towing with 20,000 lbs GCW. I get 7 MPG. I live in a rural area and as soon as I can get to auto parts store I will change out the IAT. I have spent more than $20. 00 before trying to figure out my mileage problem. Hell my dealer even ended up voiding my warranty trying to figure it out.

Ron

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1999, 3500, 6x6, slt, auto, 3. 55 lsd, Qd cab, ISB cummins, Isspro transmission temp, EGT, Boost gauges on A-piler, before and after fuel prssure gauge, DD stage 1, modified banjo bolts, K&N 0880 with prefilter, triple trailing 2001 26RKSS Tahoe 5th wheel, 1999 120hp 1800 bayliner. 20,000 lbs GCW.

 

[kaffine krazed]

Intake Air Temp sensor.

 

[cwsoules]

When I purchased my truck I got up to 20 mpg not towing and 10 mpg towing a 10K 5er. Things got worse over the last year. I now get 16 to 17 mpg alone and from 7 to 9 mpg towing. Should I have the IAT replaced? I think if I ask my dealer I'll not get a knowlegeable answer.



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Chuck
2000 Quad Cab 2500 Auto w/4:10 rear end.
Rigged to tow a 5th wheel.

 

[Mopar-muscle]

marco , how are you heating it , member massdiesel has a 99 that constantly gets 14 mpg , he has over 30k on the truck and his is broken in , towing well over 20k trailer for many miles .

i looked in my 2000 manual for table to do the test and was unable to find one , where should i look ? i also notice my grid heater cycle with a warm engine in the winter , but i get about 16 -17 on my 50/50 commute , but during the winter its around 14 .

thanks .

 

[RAMalama]

I hate to ask but I have to! What's the IAT sensor? Tried to figure it out but could'nt. I don't think I have a milage problem, I'm just soaking all this 24V stuff in.
I was concerned about my 12V dowel pin delima and took it to the dealer. They solved it within a few hours and for just 32,000 dollars! (2WD 24V HO Quad Cab 6 speed) I have less than 300 on the ODO! I owned my 95 since new, I have a lot to learn... (need to update that signature)
R/ Ian.

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'95 2WD 3500 std cab, 4:10, 5spd. 68K miles all towing 35ft 14K-lbs triple slide 5er. Completely stock but learning...

 

[Marco]

I used a hair dryer to heat the sensors. I also used one of those cheap digital termometers to read the temperature.

Please note that the resistance values I've posted are for a 01 modell. I have the values for the other years somewhere, but can't find 'em. #ad


The service manual lists them under "Sensor Air Intake" If you give it a better look you'll find them. I don't think the grid heather should cycle on once the engine has warmed up. I guess that's a good sign for a bad IAT sensor, altough my grid heather worked only at the first start in the morning.

My numbers where pretty close to massdiesel's also mine is a '99.
Marco.

 

[JR2]

Can someone out there list the part # for this sensor for the 01 trucks??

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John D. Rathert Jr.
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01 2500 Forrest Green Sport SLT+ QC LWB 4x4 Auto 3. 54 rear end with all options avail. DC Nerf Bars, DC Grill Guard, DC mud flaps, Line-X bed liner, Leer 160XL Topper, Power Edge, EZ Edge, SPA Boost/EGT Gauge on pillar mount, DTT's tc/vb combo, 275 RV injectors, DD 4" Exhaust and a KN RE0880 where the air box use to be. Fuel Pressure gauge, SS fuel lines and lift pump relocation on deck. See My Truck, Dads truck: 98. 5 3500 SLT QC LWB 4x4, Brother Truck: 92 W250 SLT CC LWB 4x4 (Dads old truck) Winter fun - 2000 Skidoo Summit 700
I am my own warranty station.
*************************

 

[24V-DSL]

Thanks, Marco... .

I think I'll just go ahead and replace it. It's not that much $$, if I think my time messing around with the testing is worth anything.

Thanks for the great information.

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White 2001. 5 2500 ST, SWB, 4X4,QC, AUTO, 4. 10's, LSD, 285/75/16 On Weld Outbacks, PIAA 510's, Line-x, Tinted glass, Redline 85+, Blow-by-bye, RE-0880 & 25-0880,muffler fell off,level truck with 2" tuff country kit, Bilsteins at the corners, Di Pricol egt and boost, Mag-hytec "original flavor" transmission pan and Dana 70 diff. cover, Westin Step Bars,DTT TC/VB,yeee-ha,EZ, Custom Plate 24V-DSL

 

[24V-DSL]

Thanks for the help, Marco.

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White 2001. 5 2500 ST, SWB, 4X4,QC, AUTO, 4. 10's, LSD, 285/75/16 On Weld Outbacks, PIAA 510's, Line-x, Tinted glass, Redline 85+, Blow-by-bye, RE-0880 & 25-0880,muffler fell off,level truck with 2" tuff country kit, Bilsteins at the corners, Di Pricol egt and boost, Mag-hytec "original flavor" transmission pan and Dana 70 diff. cover, Westin Step Bars,DTT TC/VB,yeee-ha,EZ, Custom Plate 24V-DSL

 

[radixr]

If your grid heater is cycling in a hot engine in the winter, it could be that the sensor is good, it's just that the hot engine hasn't had time to warm up the intake manifold.

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1996 Dodge 2500 4X4 SC, SLT,Cummins 12V, 5-spd. , JRE 4" exhaust (my kitty ran away into the woods and the muffler fell off!), TST 280 HP/685 Ft-Lb Uprate Kit, AFC Spring Kit, ATS 3-piece Exhaust Manifold, Chrome Valve Covers, Horton Fan Clutch, Jacobs/Ram Exhaust Brake, MagHytec Differential Cover, Prime-Loc, Rancho RS9000 Shocks, Combo Gauge, K&N Air Filter, Brite-Box, Geno's finger-touch oil pan drain plug, Optima Yellow Tops, no turbo silencer ring, full-time fog lights. As of 5-19-01, 68,522 miles.

 

[Marco]

Sure that could be radixr, but I've seen several people saying that the grid heather would cycle on at idle, after several hundred
miles...
Hard to believe that the intake isn't warm enough then.

Hope this stuff helps someone of you.
Marco.

 

[pwr2tow]

I ordered mine and will pick it up Tuesday. I will be towing this weekend over the same terrain, so will post the results after memorial day.

Marco, I need your ECM.

Ron

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1999, 3500, 6x6, slt, auto, 3. 55 lsd, Qd cab, ISB cummins, Isspro transmission temp, EGT, Boost gauges on A-piler, before and after fuel pressure gauge, DD stage 1, modified banjo bolts, K&N 0880 with prefilter, triple trailing 2001 26RKSS Tahoe 5th wheel, 1999 120hp 1800 bayliner. 20,000 lbs GCW.

 

[Archive]

Where is it located on the engine? TIA