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Old 10-08-2012, 02:04 PM
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Bad miss when cold

When I started the truck today after it had been sitting roughly 18 hours, I noticed a high idle and heavy miss. I let it run about a minute, and when under load, the miss went away. I turned a corner and as I went up the hill in 3rd, it stalled, then caught again running on maybe 4 cylinders. I stopped in a parking lot to check my UVCH connections, and it stalled. It restarted, but had very little throttle response. I removed the chip, and it restarted and ran to the point of being driveable, but still had a bad miss at idle. Only under load does the miss go away. I have new UVCH harnesses at the house, so I may swap those in. The glow plugs are a year old, the injectors are a year old, and the Stan-Cor relay is less than a year old. Yesterday when driving I noticed a slight miss, but nothing like it was today. Removing the chip seemed to help, but only slightly, which I thought was odd. Any suggestions?
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Old 10-08-2012, 03:26 PM
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How cold is it outside? How long do you let it run before driving it? Removing the chip will help defuel the injector pulse and lessen fuel squirted into the cylinder cold, meaning a more efficient burn in the cylinder.
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Old 10-09-2012, 03:51 AM
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It wasn't that cole. 35 or so. I'm thinking I had a connection problem with the chip and the PCM, because with the chip set to stock, it would start and immediately die. With it removed, however, the engine will idle without stalling. As I drove around the rest of the evening with the chip removed, the truck seemed to drive normally. I guess I'll look at all my connections when I get home and see if that was the issue.
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Old 10-09-2012, 07:18 AM
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Maybe it is a bad connection with the chip. I usually pop my PCM though at the slightest hint of a bad connection. Dude, 35 is plenty cold. Do you have a friend with the same truck that doesn't drive it all that often? Swap Glow Plug Relays with them and I'd bet you'll get a better start up.
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Old 10-09-2012, 08:13 AM
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I'm running the Stan-Cor, so I shouldn't be having relay problems. I may have connection issues though, where I connect to the relay. I may get back in and try to scrub the connections on the PCM a little cleaner. Do you think it's worth doing the UVCH's?
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Old 10-09-2012, 08:46 AM
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Pull the connectors off and look inside. If the pins are shiny brass and there is no oil in there then the Wiring ought to be good. People have found that the UVCH somehow back off the injectors sometimes. I guess if you are going to open it up the might as well do the work.
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Old 10-09-2012, 03:03 PM
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I'll check them out here in a couple days. I'm wondering if I might not have a failing ICP sensor too, but I didn't think to pull the plug yesterday when it wouldn't start.
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Old 10-11-2012, 08:39 AM
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The same situation has occurred the past two mornings. I believe I have a pinhole in a fuel line, as I've been smelling diesel, finding little diesel spots around the motor, and now am having this starting issue. I tend to think that a very small hole is allowing the fuel in the supply line to drain back to the tank, causing the fuel pump to suck air and be unable to provide fuel pressure for a 3 minute window that is almost exactly 2 minutes after starting the engine. I have fuel in the valley, I just need to pinpoint where it's coming from and I think I can fix it. I've got the full o-ring set for the fuel bowl, too. How hard are they to rebuild?
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Old 10-11-2012, 09:08 AM
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Look at the bottom of the fuel bowl and around the up pump. The lines under the bowl are prone to leaking and there is a weep hole on the pump. Get rid of this leak, diesel eats wiring. The longer it leaks the more other problems are going to show up.
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Old 10-11-2012, 09:19 AM
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Pump is new...I've got to pull the bowl and clean everything out, then drop it back in and see if I can figure it out. Wherever air is leaking in, fuel should be leaking out, shouldn't it? As long as the engine is running.
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