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Did you see the search community bar? Idle speed is a common topic. Unknown issue...

 

I did look through there and didn’t see anything with this exact problem. When it runs hard it drops rpm like that. When it’s just sitting in my yard idling while up to temp it’s at 800 RPM or so, but it drops to like 200-300 rpm after dragging a loaded trailer onto the highway with the pedal smashed through the floor like the Flintstone-mobile. I was told it was governor springs being too tight or too loose, the torque converter could be locking up, or a million other things.

 

Have you inspected the linkage? The stop is a bolt with a locknut. It could be worn or the piece that rests on it could be worn. What is the idle speed while in gear, AC on, engine at operating rpm?

 

The linkage is all fine. Idle speed in gear, AC, all warmed up at 750 rpm. I’ve had it at 800 rpm and I’ve had it at 700 rpm. 750 feels perfect, if it’s at 800 it just wants to pull too much at stop lights on its own.

 

This could be a lot of different issues. I would check your basics first. These motors run on basically 2 things, Fuel and Air. If you say you have checked your fuel then start to check for air leaks. You could have a leaking boot or something. Only way to really tell if you have a leaking boot is to take your ends off the turbo out let and the inlet on the motor and seal them off then pressurize them to about 40PSI and then hold it for a while and see if the PSI drops. But thats where i would be looking next.

 

I actually had a serious air leak about a year ago. Fixed that and threw a new turbo on it, same time I check for boost leaks in the system. It held pressure well. I don’t think it’s air.

 

Have you checked your injector seals. Could be leaking air at the cylinder then

 

I did delivery valves and injectors over already.

 

Just because you did them does not mean they all went in correctly and are not leaking. More times then not the things you mess with are the things that are causing your issues.

 

I only did them bc the delivery valves were leaking, I made sure to be precise and check them after install.

 

Im just giving you some trouble shoot procedures. If you think they are good then leave them. As I dont know your mechanical ability I cant say much after that. Do you get any white smoke during start up? dose it black smoke a little bit when you take off hard from a stop?

 

I understand, it shoots black smoke no matter what, if I’m very gentle on the throttle it’s under control, but typically shoots black smoke a decent amount. I’ve done all kinds of adjusting of the AFC and fuel plate yet it still smokes a lot.

 

Thats a very good indication of not enough air in the cylinders. Can your read how much boost pressure you have?

 

I push 40psi max pressure, round 2000rpm I’m at about 28psi typically. Reading from the intake horn.

 

hmmmm. interesting. have you messed with the timing of the Injection pump?

 

Yup it’s set to 17 degrees.

 

Lets go back to the dragging tq converter theory. If it is 4WD have you shifted the transfer case to neutral when the engine RPM drops so low? If it is a fuel or air issue it would misbehave every time you go to idle.

 

Yeah, The being speratic kinda just threw me off. I never really hurd of a dragging TC normally they just dont work lol

 

I have not put the T-Case into neutral while it happened, I didn’t think it would change much versus putting the trans in neutral. Yes it is very speratic though.

 

Having the T-Case in neutral should put the whole drive train in Neutral and if it was a dragging TC it would make it idle back to normal.

 

If that doesn’t do anything I’ll be back, I’m going to try that next time it drops the idle

 

I hope it works for you. GL

 

I have the exact same problem with my 97 3500 2wd. When its really hot and the A/C running, just turning the steering wheel will kill the engine. It's done it before and after a transmission rebuild. I'll check for a boost side air leak because I have noticed the boost pressure is getting lower. strange tho even when I would make 35psi under full boost, it would still die.

 

Yours sounds more like a problem with the engine not up idling when the A/C turns on or the PS pump puts a load on the engine. Then engine should automatically up idle when you turn the wheel full lock even with A/C off. I personally do not know what controls this on the 12V; I would assume it has something to do with your linkages and stuff on the injection pump whether it be VE or P-pump but I cannot answer that. Maybe some on here who knows a little more about those pumps can put a word in

 

The truck finally acted up again. Putting the t-case in neutral did not change it. I have come up with another theory though. I don’t know if it’s possible but I’ll see what y’all think. I have a FASS lift pump on the truck, it pushes like 50 psi according to my fuel pressure gauge. Is there any way that there is too much fuel pressure and it’s forcing the fuel return spring to stay open all the time and not have enough pressure actually at the injection pump? I’m just throwing stuff out here at this point before I start buying parts to swap out lol

 

well one thing for sure that is too much fuel pressure out of the FASS. It should be no greater than 24PSI. Idk if that is whats causing your issue but Normally people read around 16-20PSI to the injection pump.

 

I guess you are lost? P-Pumps require 17 psi minimum. 50 is just fine.