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Dropping below idle

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I have been towing my 5er across Texas on the new rebuilt motor.  Started with 1100 miles on her, I am about  750 miles into trip. hot as hell out here. I have been running in 4th gear, nv4500, at 2500 rpm, right around 64ish mph. Wierd thing has started to happen when I start slowing down for an off ramp for fuel, or rest.  When the clutch goes in and I amdown shifting as I slow, the idle wants to drop to about 700 before it catches itself and comes back up to about 825ish. After I stop, it smooths out and idles perfect? 

 

Anyone ever heard of this?

 

All sensors where replaced during rebuild...

Edited by Mariocand

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  • trreed
    trreed

    12 valve tappet cover...  Hard for the seal to blow out when there's a breather right there!

  • TFaoro
    TFaoro

    Two 3/4in heater hoses and a 1/2in heater hose on mine and I've never had an issue with them trying to kink. I think if they did it would blow the hoses back open   Anything is possible with en

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  • Owner
3 hours ago, Mariocand said:

I have been towing my 5er across Texas on the new rebuilt motor.  Started with 1100 miles on her, I am about  750 miles into trip. hot as hell out here. I have been running in 4th gear, nv4500, at 2500 rpm, right around 64ish mph. Wierd thing has started to happen when I start slowing down for an off ramp for fuel, or rest.  When the clutch goes in and I amdown shifting as I slow, the idle wants to drop to about 700 before it catches itself and comes back up to about 825ish. After I stop, it smooths out and idles perfect? 

 

Anyone ever heard of this?

 

All sensors where replaced during rebuild...

 

Yes... I hate to say it my +75HP injectors from DAP did this. They turned out to be carboned fouled. I'm in the process of sending them back to be looked at. Mine was much worse it would drop to 500 then surge to 1,000 RPM and continue till you stopped. Then idle at a perfect 800 RPM. Then if you launched again it was prone to stalling out. 

 

 

  • Author

I pretended that i didnt read what moparman said until i finished my trip. Ignorance is bliss I suppose. However, I found that I could prevent it from happening by rev matching my down shifts and popping the throttle once when I would get to a stop and be in neutral. Stop the issue completly. 

 

On a side note,  and probably needs it on thread,  but I just have to say that the mishimoto radiator I put in during the build,  is one of the best investments I have done to the truck. 100+ abiant temps, pulling 14k at 65mph at 5000' above sea level caused it to max at 212° going over some of the steeper passes.  But the speed at which it recovered from it was incredible.  As soon as the load was removed from the motor it started dropping. It held around 197-203 in the flats.  Had the A/C on the whole time and the cruise set.  Made for a great first trip on the motor. Worth every penny. 

20170514_161034.jpg

Edited by Mariocand

Was your old radiator leaking?  I had issues with my truck overheating several years ago.  I removed the radiator, soaked it degreaser and hit it with a pressure washer and it was like you said after I re-installed it...night and day difference.  Your old radiator is pretty dirty, have you done anything to re-route the crank case breather?  If you haven't, your new radiator will eventually look like the old one.

  • Author

I have rerouted it back to where it dumps out next to transfer case. I didn't get all creative like moparman did with the pvc pipes, but just used a long 3/4" heater hose ran over the top and down along the frame next to fuel line. That oil buildup was caused by front main seal or from the tappet cover leak. 

  • Owner
46 minutes ago, Mariocand said:

I didn't get all creative like moparman did with the pvc pipes, but just used a long 3/4" heater hose ran over the top and down along the frame next to fuel line.

 

Get ready for blown tappet cover gasket... This for sure will cause a failure when the hose starts to get mushy and kink shut. I've warned several people not to use heater hose. One ended up stranded on the Alcan Highway when his tappet cover blew out because of the crankcase vent (heater hose) kinked shut.  I highly suggest you get that yanked off very very soon and switch back to hard line like PVC or similar. 

12 valve tappet cover...  Hard for the seal to blow out when there's a breather right there!

    • Like 1

    I saw one pop up on Facebook pretty recently for like $50...  Then Tyler got his billet one so I grabbed his

    1 hour ago, Mopar1973Man said:

     

    Get ready for blown tappet cover gasket... This for sure will cause a failure when the hose starts to get mushy and kink shut. I've warned several people not to use heater hose. One ended up stranded on the Alcan Highway when his tappet cover blew out because of the crankcase vent (heater hose) kinked shut.  I highly suggest you get that yanked off very very soon and switch back to hard line like PVC or similar. 

    Two 3/4in heater hoses and a 1/2in heater hose on mine and I've never had an issue with them trying to kink. I think if they did it would blow the hoses back open :lol: 

    1 hour ago, trreed said:

    Though, Tyler managed to blow out the seal on the 12V cover with the p pump..... So it is possible.  But he also had deleted the stock breather by then, so it was destined to happen

    @Mopar1973Man  http://www.ebay.com/itm/94-98-Dodge-Ram-5-9-Cummins-Diesel-Tappet-Pushrod-Cover-12-valve-6bt-3911821-/152482257077?hash=item2380a698b5:g:bJ4AAOSw5cNYOkQk&vxp=mtr

    :hijack:

    Anything is possible with enough fuel and air!

    • Like 1
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