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Sooo sick of defueling!!!!!

Deere Freek

Deere Freek

Recruit
Messages
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Location
Hastings, MI
Ok, I have a home made tm set at 8 psi and my truck throws codes left and right whenever i have a trailer hooked up or drive 70 on the highway. It defuels and i have no power at all and I HATE IT!! :mad2: :mad2: :mad2: :mad2: :mad2: :mad2: :mad2: :mad2: :mad2: :mad2: I think it's because of high iat's but my egt's never get over 1000 for the most part. Is there anything i can do to fix it other than a gl4? i don't want to spend the 500 at this time, i'm buying a 25 foot gooseneck trailer next month and am trying to save money. I have a boost fooler already and i know that works, right now i want to fool the iat sensor if it won't do any harm. I have guages and keep a close eye on things.
 
De-fueling can certainly be annoying - I understand. But, it's doing it for a reason. If you're positive it isn't the high boost, then the question is, what is it? You mentioned 8psi, but noticed in your signature 12psi?

Let's start with the codes. What codes are you getting?
 
A snap-shot with a scan tool connected on a de-fuel run would be ideal.
 
Shouldnt have high IATs driving 70MPH. How did you wire this boost fooler?

What is the boost while youre cruising? Is it 8psi cruising, which is high, but I only see 150*F IAT when my boost jumps to 10psi and I have the underhood cone filter.

are you correcting speedo for taller tires?
 
My truck was hitting 245f and defueling with less than 10# boost quite often.

I think we had a chart somewhere on here or the other site that showed the factory parameters for temp vs resistance on the IAT sensor. It should be an easy task to solder a radio shack resistor into the harness as a temporary fix. It should be pretty simple math once you decide where you want the resistance numbers fooled to. I do know for sure that the sensor has more resistance the colder it is. I dont think you need much of a resistor to change the function quite a bit. If you want the numbers off the chart let me know. I would post it tonight but it is late and I am pretty sure my manual is at the other end of the city in the shop. You might have to PM me so I get an email if I forget to check back.

I can not see why it should hurt anything as long as you watch the EGT.
 
DennisG01 said:
De-fueling can certainly be annoying - I understand. But, it's doing it for a reason. If you're positive it isn't the high boost, then the question is, what is it? You mentioned 8psi, but noticed in your signature 12psi?

Let's start with the codes. What codes are you getting?
Click to expand...

I turned it down because of the problems. The only thing i can figure is high iat's.
 
buddy said:
Shouldnt have high IATs driving 70MPH. How did you wire this boost fooler?

What is the boost while youre cruising? Is it 8psi cruising, which is high, but I only see 150*F IAT when my boost jumps to 10psi and I have the underhood cone filter.

are you correcting speedo for taller tires?
Click to expand...

I wired the boost fooler inline with the manifold pressure sensor and i know that's doing it's job because i can turn it up and down and it allows so much boost accordingly.

I do have 265's but the speedo is dead on, tested with a gps and police scanner.
 
Do you have an EGR in that C2500?

I suppose if you came stock with 31" 245/75/16 then 32.25" 265/75/16 isnt far off or someone corrected for it.

Now mine came with 235/75/15, only 28.75" tall, so when I put on 30.5" 245/70/17 the speedo is 5MPH off at 65MPH. The error increases the faster I go. Its only starts to be really off after 30MPH.
 
Matt Bachand said:
I don't understand how your boost fooler would adjust boost if you have a mechanical wastegate?
Click to expand...

It doesn't adjust boost, If i have the boost fooler turned down then it defuels as to not blow a head gasket. It's the computer that does it. If i have it turned up then boost pressure doesn't affect anything, However i am still having defueling problems with it turned up. I assume it's high iat's. What i want to know is if it is ok with an egt guage and all to fool the iat sensor. and if so how do i go about doing it.
 
buddy said:
Do you have an EGR in that C2500?

I suppose if you came stock with 31" 245/75/16 then 32.25" 265/75/16 isnt far off or someone corrected for it.

Now mine came with 235/75/15, only 28.75" tall, so when I put on 30.5" 245/70/17 the speedo is 5MPH off at 65MPH. The error increases the faster I go. Its only starts to be really off after 30MPH.
Click to expand...

No egr, "f" engine. THe truck had 265's on it when i got it from the po and i assume he could have corrected the speedometer.
 
Check resistance accross the IAT sensor. Its not as useful as the Engine coolant temp you should check too, same thermistor values. Thats because you can increase water temps at idle and theres a guage, but IATs flucuate so much youll never get 100* at idle unless its 100* ambient. So you can check it at ambient to make sure at least thats right. You could set up a digital multimeter across the IAT sensor and run the leads into the truck and monitor it while driving. Or get a scanner.

32*F 9420ohms
50*F 5670ohms
68*F 3520ohms
86*F 2238ohms
104*F 1459ohms
122*F 973ohms
158*F 467ohms
176*F 332ohms
194*F 241ohms
212*F 177ohms
 
Deere, did you get those codes pulled, yet? I'm not sure if high IAT's will hurt anything if, like you mentioned, you keep an eye on EGT. But, there's still gotta be a reason why you're defueling - what's causing the IAT? With what you've posted, there seems to be an underlying cause. Don't want to be masking a problem.
 
I'm a little late to the party, VERY busy at work as of late, something else to consider is bad MAP sensor, I had one go bad high once and it was defueling me but not setting a code, it should have coded for boost out of range but it didn't, by gauge I was reading fine with boost, but by input via MAP sensor the PCM sees I was defueling on high boost @ 35psi :eek:

I'd also be looking at the IAT sensor 8 psi boost should not make mega high IAT unless it is 90+F outside air temp also
 
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