Appologies if this has been asked and ansered. I seasrched here and I did check the a/c wiring and it's ok.

the truck: 2003 ho 3500 dually auto, bone stock

The issue:

300 miles from home with big camper on the back, and after pulling like a HORSE up some big hills, stopped to get some cherries at Keremeos (Highly recommended, btw).

It started no problem then I took her out on the road...about 20 seconds later, with mild throttle applied, the engine goes to idle, then to 2krpm or so, then idle, then 2k all in about 2 seconds. I pulled off the throttle, and the road, sphincter fully tightened. Thank god there was room!

The engine continued to idle, then I tried it and off we go, like nothing ever happened. It pulled like a HORSE again all the way to the Kootenays.


ANY ideas? It still has the stock lift pump, but it sure doesn't seem like that's the issue with such a quick issue. If I didn't know better I'd think throttle sensor input or computer snafu somehow????


Thanks all,

Chay

 

I got a bit more info when I read the codes. Hopefully they are not stale!

P0633- Key not programmed. I guess this is common after a reflash
P0107- P0107 Manifold Absolute Pressure/Barometric Pressure Circuit Low Input
P0073-AMBIENT TEMP SENSOR HIGH

So, my thoughts are that a bad map sensor could cause the last 2 and my defueling issue.

The low map would cause the defueling, and the loss of the temp in the same sensor would cause the readins of the map temp and the ambient temp to conflict, setting the ambient temp failed code.

I'm going to check the harness, 'cause it seems like maybe they are losing their power supply somehow???

Thoughts?


Chay

 

I think I found it.

The connector on the map sensor was missing the cross piece that holds it together...it could back off by itself.

I tie-wrapped it in...hopefully that's the end of that!!


Chay

 

Great detective work!

 

Glad we could help you!!..... Oh wait... never mind

Hope that was the problem.

 

GOOD WORK Rockcrawler

 

One more thing I learned in case someone is looking at this in the future.

The connector I fixed was actually on what is called the iat, intake air temp sensor, which is in on the air filter housing, and is a 4 wire device. Somehow the P0107 refers to this sensor, not the map sensor which is in the intake elbow, by the head, post turbo. It's said the map sensor issues are captured by under/over boost codes.


I suspect the iat is not just an iat, but is also what i'm used to calling a baro sensor in gas fuel injection. That is, it measures ambient barometric pressure as well.

It could be a bit more tricky than that, come to think of it. If we have temp and pressure pre-turbo, and pressure and temp post-turbo and we know the running conditions of the engine, and the adibatic efficiency of the turbo is known, perhaps the sensors check against each other. So maybe either one can cause the P0107??



Anyway, it's too early to say i found the problem for sure given the intermittent nature of it, but it adds up.

Thanks for reading guys!


Chay

 

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