truck stalls when engine drops to an idle

[stang1999]

well i got my transfer case rebuilt and now for whatever reason whenever the truck is facing downhill and i put it in neutral it dies out.

the check engine light came on but i’m pretty sure it’s the bank one sensor one O2 sensor because that’s what it was last time and i never fixed it. It’s either that or the idle control valve.

i pulled the idle control valve and it seemed pretty gunked up but i reinstalled it for the time being.

i’d love if someone hopped in and have some feedback

it’s a 1997 5.2 V8 with a NV3500 4x4

 

[Nick_rp]

Uhh, try cleaning the IACV?

 

[stang1999]

Uhh, try cleaning the IACV?

i replaced both O2 sensors, air filter and the IAC valve. my next guess would be fuel filter/ fuel pump. but my fuel railed doesn’t have the schrader valve so i csnt really text the fuel pressure.

 

[stang1999]

Uhh, try cleaning the IACV?

my speedo stopped working and it threw a code but i’m sure that’s jus me messing something up on my rebuild and i can just get a new sensor, i’m sure it can’t be related

 

[Dan98]

It has fuel pressure or it would drive. If you have had a low or dead battery lately the computer needs to be reset or they stall going back to idle.
The speedometer wires plug in tail shaft of transfer case that can mess with you if it's not reading. Cycle the key on off 5 times stopping with key in run position then read the first 3 codes we go from there

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[stang1999]

It has fuel pressure or it would drive. If you have had a low or dead battery lately the computer needs to be reset or they stall going back to idle.
The speedometer wires plug in tail shaft of transfer case that can mess with you if it's not reading. Cycle the key on off 5 times stopping with key in run position then read the first 3 codes we go from there

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i cycled the key to the run position and left it ij the run position on the 5th time and it just says “12” on my odometer. what now?

i had just thought that the fuel filter could’ve been clogged and just bogged out when it slows down

let me know what you think i appreciate the help!

 

[Dan98]

12?? Humm the check engine light should start to flash in sequence so 3 quick flashes a short pause then 2 quick flashes is 32 know what I mean? With the service manual Chilton I have those codes are as good as a factory scanner

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[Nick_rp]

Im not no cummins expert but when the symptoms are angle related like going down hill, its most likely the tank, like the fuel pick up tube rusted and broke or not seated properly.

Do you know if the tune was ever altered? While under no load, foot off the pedal, neutral and going down hill the injectors should all but stop pulsing and start again once you hit the pedal. Possibly not recovering. Might look at getting the ecu reflashed.

Thats all i got so i hope this or someone can help. Good luck

 

[stang1999]

12?? Humm the check engine light should start to flash in sequence so 3 quick flashes a short pause then 2 quick flashes is 32 know what I mean? With the service manual Chilton I have those codes are as good as a factory scanner

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yeah just tried it again and the same thing happened. no flashes from the check engine light but the odometer changed to “12” and it’s not my trip meter. another thing i noticed is that when i do that key trick the check engine light turns off. thoughts?

 

[Dan98]

It just says you disconnect the battery in the last 50 key cycles

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[stang1999]

It just says you disconnect the battery in the last 50 key cycles

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i got a p0500 code so i bought the speed sensor in the rear diff. i’m hoping that will solve my no speedo, check engine, brake, and abs light situation.

i’m also running some sea foam and i’m gonna clean the throttle body to see if that solves the stalling issue.

 

[Gr8bawana]

i replaced both O2 sensors, air filter and the IAC valve. my next guess would be fuel filter/ fuel pump. but my fuel railed doesn’t have the schrader valve so i csnt really text the fuel pressure.

Just a thought, did you spray some throttle body cleaner into the hole where the IAC valve goes?
There is a very small opening in there which is what the IAC valve controls. If the valve itself was gunked up like you said the tiny hole might also be plugged.

 

[stang1999]

Just a thought, did you spray some throttle body cleaner into the hole where the IAC valve goes?
There is a very small opening in there which is what the IAC valve controls. If the valve itself was gunked up like you said the tiny hole might also be plugged.

no i did not! i’ll go check it. i’m planning on removing the entire throttle body and cleaning it but that might be a quick fix.

i might just go drench it with carb cleaner and my air compressor

 

[stang1999]

It just says you disconnect the battery in the last 50 key cycles

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i cleaned the throttle body and got any junk off of it and i took it for a test drive and nothing died on me.

my speedo still doesn’t work but i’m assuming that’s a separate problem

 

[Dan98]

This 5.9 is a gas right at least you make it sound that way. Anyway the TPS sensor can make weird things happen stalling shifting hard starting. Should code tps
Coil pickup in distributor make it quite with no restarting until it cools off with no code showing

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[stang1999]

This 5.9 is a gas right at least you make it sound that way. Anyway the TPS sensor can make weird things happen stalling shifting hard starting. Should code tps
Coil pickup in distributor make it quite with no restarting until it cools off with no code showing

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it’s a 5.2, i have a 24v cummins but this 5.2 is my daily. if i have my info as my 1999 24v i apologize.

i cleaned out the throttle body and it seemed to be fixed.

what would happen is that the idle would drop to 200-300 and die whenever i would push the clutch in when coming to a stop.

now the rpms aren’t dropping below 500/600 and it’s not stalling out. and i’ve only driven it once since the cleaning but it seems to be good.