Rough Idle
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Rough Idle
I am at the end of my rope guys. I have replaced injector o-rings, ICP, IPR, CPS, and IDM and I still have a rough idle constantly and erratic ICP pressures and hard start when hot. This is ridiculous. I have to hop out of my truck to give her a shot of ether in the Wendy's drive through to get her going again. I have done everything short of replacing my HPOP. When I first fired her up after doing my injectors, she idled so smooth it acted like a new truck. What is going on here?
Tuned
Joined: Nov 2019
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Your symptoms are an indication of possible worn injector poppet valves. Some ways to diagnose this is a Buzz test and or pull the valve cover to check armature gap for indication of wear. Do you have an idea of how many miles are on the injectors? Also what oil are you running? The problem is due to leaking upper poppet valves. The hot oil easily bleeds off which cause the symptoms you describe.
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The injectors are factory at 316,000 miles. I know they are worn but the buzz test sounds fine and the truck runs great but it just doesn't start very well. After I did the o rings, it cleaned up a lot of the black smoke. Do you suppose there's still air in the system? I did drive it aggressively for about 50 miles when I first started it. I run 15w40 Rotella Semi Synthetic with Hot Shot Secret's stiction additive.
Tuned
Joined: Nov 2019
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That sticrion additive might be why the buzz test sounds good. You can try simple things like swapping out the CPS. Unplug ICP sensor and see if it still idles rough. What does your ICP look like when cranking and idling rough? Also look at IPR% when idling to see what they are doing.
Mountain Pass
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I tried the ICP trick. There was no change. I have two different Motorcraft Cam Sensors. They don't change anything. ICP makes about 300 psi after 5 seconds of cranking. IPR goes to 55%. When it's running, the IRP stays around 12%. The ICP varies from 540 to 620. It jumps quite a bit and you can hear the surging. I just bought a HPX crossover from RiffRaff to help with that.
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When I put the crush washers on, I put the ridge side up like Stephen *** showed in his O-Ring video. I followed his instructions and was very meticulous about each one. Extra oil on the injector and o rings the entire time. I walked the o rings around with a pick on every one when I got them seated. When I put them back in, I put enough oil to drip off and I tapped them in with a rubber mallet until it bottomed out then I torqued them down to 15 pounds of torque.
Tuned
Joined: Nov 2019
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So what was the symtoms that made you change the rings in the first place? Was the parts you replaced motorcraft parts or aftermarket. When it comes to these engines it is best to stick to motorcraft or Alliant for injector parts and o rings. Your symptoms of a truck that idles runs smoothly cold and gets rough when hot still typically points to worn injectors. 300+K on a set of injectors is usually beyond the time for new injectors. I would remove the valve cover and check armature gap on the injectors to gauge the wear. You don't need to remove the injector to check gap. Just need to remove solenoid. You can also run a CCT and see if it points you in the right direction. Other ideas are unplug injectors one at a time and fire it up to see if you can point out a problematic injector I've done that to diagnose 7.3 injector issues plenty of times.
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My truck was just running rough. It wouldn't start at all when it was hot. I pulled off a valve cover and saw oil seeping out from around injector 2. I figured that with 300k, it was time to do o rings. Everything I put on my truck comes from RiffRaff Diesel. Everything is Motorcraft or Alliant. When my truck idled before I did o rings, it would shake the mirrors. Hot or cold. It just wouldn't start at all when hot and it struggled a little bit when it was cold. When I started my truck after first doing my o rings, it was so much smoother and quieter.
Tuned
Joined: Nov 2019
Posts: 302
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My truck was just running rough. It wouldn't start at all when it was hot. I pulled off a valve cover and saw oil seeping out from around injector 2. I figured that with 300k, it was time to do o rings. Everything I put on my truck comes from RiffRaff Diesel. Everything is Motorcraft or Alliant. When my truck idled before I did o rings, it would shake the mirrors. Hot or cold. It just wouldn't start at all when hot and it struggled a little bit when it was cold. When I started my truck after first doing my o rings, it was so much smoother and quieter.
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I know my injectors need replacing. I was planning on getting 180/30 Full Force Diesel injectors and do stainless steel RiffRaff injectors cups and everything next summer when I can work full time and make good money. I just need my injectors to last till then.
Tuned
Joined: Nov 2019
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So shimming an injector to gain armature to body top clearance is too band aid an injector when it starts rough cold and runs fine once warmed up. This is due to the cold oil causes the armature plate to stick (stiction) to the body top. Unfortunately shimming an inector will not fix a worn upper poppet valve seat. The cheapest way to fix this issue is to use good core injectors and pull apart the top of the injector and swap poppet valve and upper top and or seat parts. There are also shims for the upper seat. This can be carefully accomplished without removing the injector. You would pull the solenoid off then the armature plate then the 4 body top screws and the poppet valve and spring will be accessible. The only other way I see to limp this issue by is to pull the thermostat and run without one. The downside is the engine will take much longer to warm up (no cab heat) and run substantial cooler. This will keep oil temps cooler and hopefully allow it to hot restart. I have ran 7.3s with stuck open thermostats before.