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6.9 IDI Rough Running/Stalling/Throttle Response

 
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Old 04-14-2019, 02:13 AM
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6.9 IDI Rough Running/Stalling/Throttle Response

So my 86 6.9 had sat for 6 months from a bad transmission, which I finally repaired. I filled it with fresh gas and started it, took about 8 seconds of cranking. It sounded rough for about a minute and everything was good. I drove it around for like 2 days and set my VRV to the point it drove happy. I thought everything was swell, so I drove 100 Miles with the truck. It started having some bad delayed throttle response issues. I could press the pedal pretty far down and the engine wouldn't change RPM for almost 3 full seconds. Then it would go, didn't matter if I did this at the Injection pump or pedal, so it's not a throttle linkage problem. So I thought maybe my fuel filter was bad so I replaced my fuel filter and it took a bit of cranking(about 10 seconds) and it came back to life, seemed to run normal that night and I thought all was well.

Next morning came and I tried to start the truck, it nolonger starts within a second, it now cold always takes about 4-8 seconds of cranking and it will sputter, shake violently, and start with what sounds like valve train noise or VERY LOUD combustion cycles, it will then either smooth out and go to normal OR it will then start sputtering and running like crap. If i press the throttle down it will smooth out and sound normal, and drive, it seems to have plenty of power too. Then it started surging while cruising, while at a constant speed, it will suddenly feel like someone just stepped on the pedal and gain some serious acceleration(about 10-15mph worth), and letting off the pedal stops this from happening. Coming to a stop the engine while decelerating sounds like it's missing, and then approaching a stop, sometimes not always it will begin shaking and running very rough, with a small bit of white smoke from the exhaust, the engine will then either stall or it will smooth out. If the engine stalls it will take over a minute of on and off cranking to get the engine to restart, regardless of throttle position. Both tanks were full, both tanks have no difference. I've run some seafoam through the system, and now i've tried running diesel kleen through. Running some diesel kleen through has made the throttle response normal again(for tonight, might be slow again tomorrow, we shall see)

I've replaced my fuel filter, and now I've ordered a Lift pump for my truck, but it's really starting to sound like a bad Injection pump to me

Unknown miles on the truck, it's rolled over at least once, but as many as 3 times.

Anyone have advice or suggestions? It's starting to really upset me, everything possible has been breaking on this truck.

EDIT: Attempting to floor the truck it will not always redline in 1st at the same speed(no tach but engine speed sounds different, sometimes it stops at 30mph, other times it stops at 35), I think the governor is having issues in my IP, or I have air in the system during that time
 
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Old 04-14-2019, 08:08 AM
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pull the fuel filter off and pour it out.
fill with ATF and put back on. start engine and let idle for 30-45 seconds. then shut it off.
let sit for 12-24 hours. the longer the better.
after sitting fire it up and drive it like you stole it.
the ATF cleans out the injector pump and injectors. driving it like you stole it blows all the crud out of the pump, lines, and injectors into the cylinders to get burned off.
 
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Old 04-14-2019, 08:42 PM
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I'm trying that, when I removed the fuel filter it was 90% full, looked like it had some air in it
 
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Old 04-15-2019, 02:47 AM
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Air intrusion will cause that unexpected acceleration thing, and could explain the other problems as well, so that's likely the cause. Where it's coming in may be challenging to figure out.
 
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Old 04-15-2019, 02:52 AM
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Originally Posted by '88 E-350 View Post
Air intrusion will cause that unexpected acceleration thing, and could explain the other problems as well, so that's likely the cause. Where it's coming in may be challenging to figure out.
I have a feeling based on other things may just have a bad lift pump
 
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Old 04-15-2019, 07:15 AM
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you could very well have air intrusion. but the ATF will not hurt, and i bet you will notice a big difference in the way it runs after you clean it out.
i do the ATF thing once a year.
 
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Old 04-16-2019, 12:00 AM
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ATF has been done, no change in how it runs, other than while driving hard, my truck died, and now will not run anymore. Bleeder port is dumping air, getting no fuel, tank has half full, have a bad feeling my sender is broken

Alternate theory here, I THINK my tank selector is leaking air, as i think it's pulling air from my rear tank even though front is selected, the issue didn't start till i ran out of fuel in the rear tank and switched to my front tank, the issue never appears while just idling. This is definatly an air issue

While driving i had another sudden acceleration event, i let off the throttle and immediately the engine runs rough, if i get out and push the bleeder(with the engine running) it bleeds a considerable amount of air, then starts shooting fuel, then the idle smooths back out and it's good till i go again.

Some of my fuel lines don't look great, i think i need to overhaul the fuel supply system!

EDIT: Filled my rear tank with 10$ of fuel and my front tank to full, truck was able to restart and go, and truck showed NO SIGNS of running issues. Gonna pull the bed and inspect the two senders and the tank selector
So air intrusion it is, followed by i think broken fuel sending units and a leaking fuel selector valve, fun
 
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Old 04-16-2019, 11:14 AM
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I've had moments where one tank being completely empty seemed to let air into the system over night even tho I was switched to the tank with fuel well before parking. I've also had an occasion where it wouldn't start, tried for a very long time without any luck. I then switched the tank selector back & forth and it started. Maybe just a coincidence, but I'm guessing the valve had stuck between tanks and not letting fuel through, tho I don't know if there's an in between position were that could happen.

At least you were able to verify that air is the problem, half of your diagnosing is done.
 
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Old 04-16-2019, 05:05 PM
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Originally Posted by '88 E-350 View Post
I've had moments where one tank being completely empty seemed to let air into the system over night even tho I was switched to the tank with fuel well before parking. I've also had an occasion where it wouldn't start, tried for a very long time without any luck. I then switched the tank selector back & forth and it started. Maybe just a coincidence, but I'm guessing the valve had stuck between tanks and not letting fuel through, tho I don't know if there's an in between position were that could happen.

At least you were able to verify that air is the problem, half of your diagnosing is done.
Yup, after being stranded in the cold for 4 hours I'm halfway there

Pulling the bed off today
 
 


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