Throttle Body????
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Junior User
Joined: Feb 2003
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From: Clarksville,TN
Throttle Body????
My '99 7.3L PSD is experiencing an erratic idle. It just started a couple of days ago. Doesn't matter if its cold or up to temp. Runs fine other than the idle surging. Also doesnt idle down properly at stop lights, etc. Do these have a throttle body and if so where is it so I can clean it. Thanks.
Fleet Owner
Joined: Jun 2004
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From: Rio Rico, AZ.
Originally Posted by Picard
So what could be the cause of the idling problem?
If it were my truck I would also check into the Injector Pressure Regulator. They commonly fail. Also the sensor on the left cylinder head that reads the HPOP pressure.
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Junior User
Joined: Feb 2003
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From: Clarksville,TN
After searching several threads, I decided to get an oil change. It was almost time. I change it every 4k miles. To my amazement the problem cleared up within a day. Who knew?
Fleet Owner
Joined: Jun 2004
Posts: 25,090
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From: Rio Rico, AZ.
Originally Posted by Picard
After searching several threads, I decided to get an oil change. It was almost time. I change it every 4k miles. To my amazement the problem cleared up within a day. Who knew?
Seems like that's the first thing to try even if it's not due for a change.
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Just remember - the PSD runs the injectors by oil pressure. When the oil gets old, the anti-foaming additive becomes depleted. So if you have oil foaming a bit, it isn't going to run the injectors properly. Rough idle and worse should be expected.
As an aside, my brother has 5 or 6 different PSDs in his business. One is an Excursion. One day it stopped running. It would start, run for a minute or two, then die, just like a gasser with a bad fuel pump. Turned out that someone wasn't watching the oil level close enough. I'm not sure how low it was, but it was low enough that the HPOP couldn't pressurize the injectors properly. Filled up with oil, problem fixed.
A mechanic said that as soon as you get more than two quarts low (the add line) you could start losing oil pressure to the injectors.
As an aside, my brother has 5 or 6 different PSDs in his business. One is an Excursion. One day it stopped running. It would start, run for a minute or two, then die, just like a gasser with a bad fuel pump. Turned out that someone wasn't watching the oil level close enough. I'm not sure how low it was, but it was low enough that the HPOP couldn't pressurize the injectors properly. Filled up with oil, problem fixed.
A mechanic said that as soon as you get more than two quarts low (the add line) you could start losing oil pressure to the injectors.
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Junior User
Joined: Feb 2003
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From: Clarksville,TN
It seems I spoke to early. I got in it today and it had the same erratic idle between ~600-800 rpm. You can watch the hand cycle up and down. I think i'll order a cps just as a precaution. Any other suggestions?
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Joined: Jan 2006
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From: Colorado foot hills
rough idle
My vote is for the D/M flywheel. I had a '97 that had the same thing. Dealer accused me of putting gas in with the diesel. Did a fuel test, no gas, replaced all the injectors, no joy, finally replaced the D/M flywheel. Lucky me, was all done on extended warranty, only cost me $100.
Seems as though the springs in the D/M get weak, and this leads to the flywheels 'talking' to each other at idle. Makes the darn thing idle rougher than anything, but can be intermittant.
If your truck sounds like a sack of cans when you shut 'er down, you probably need a new flywheel. Good luck.
Seems as though the springs in the D/M get weak, and this leads to the flywheels 'talking' to each other at idle. Makes the darn thing idle rougher than anything, but can be intermittant.
If your truck sounds like a sack of cans when you shut 'er down, you probably need a new flywheel. Good luck.
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Junior User
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From: Clarksville,TN
Actually had a new flywheel installed with a new tranny ~50k miles ago. And it did sound like the truck was about to fly into a million pieces. No noise like that at all now. Just a fluctuating idle.
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