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Discussion Starter #1 (Edited)
I was going to stick this in the "What did you do to your 6.0 today" thread but it seemed too involved for that. I am posting it because the no-throttle-response is a problem that - in particular - seems to have a mish-mash of less-than-helpful information on the interwebs.
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So... I have been really busy with work stuff and my 6.0 has been disassembled and ignored. The original reason for the teardown was to address a intermittent no-throttle-response, an exhaust leak somewhere in the up-pipe area, and a perpetual lack of power. I also had a quick change of coolant temp sometimes.

Intermittent no-throttle-response
I didn't have much to go on on the no-acceleration-from-stop. No codes or anything noticeable on the monitor. I would expect codes if the actual pedal was misbehaving but ???.

The symptom was that - randomly - it would just sit and idle when I wanted to accelerate from a stop. Mostly, it was just inconvenient but - in some driving situations - a bit alarming.

The research suggested a) the pedal; b) the IPR valve; c) the ICP sensor; d) some assorted nonsense that was just craziness.

On my truck, I have had IPR "history" - a wiring harness short that is described here:

http://www.powerstroke.org/forum/6-0-motor-problems/1096562-6-0-harness-chafing.html

In addition, when I did my oil cooler relocation, I was not able to remove my IPR valve to check the screen. It would. not. budge. You can read of my complaint here:

http://www.powerstroke.org/forum/6-0-motor-problems/1019649-ipr-valve-removal-sawzall-tnt.html

Whatever happened, I was going to get to that screen this time around.

Exhaust Leak
One time while driving, I heard a distinct change in the engine sound. I thought that a boot might have slipped, but nothing. Then I began to have exhaust coming into the cab at stops.

I tried to see the problem while it was together, but couldn't. Based on the exhaust particulate, my only guess was the turbo itself was leaking, but that seemed a weird idea.

Low Power
The lack of power is - of course - related to the exhaust leak above, but the truck has always seemed a bit doggy since I bought it. During my oil cooler relocation, I replaced a leaking exhaust manifold. That seemed to help.

Quick coolant temp change
A quick change of fluid temperature is 99.99% sensor- or wiring-related. Thermal processes aren't fast. So... in the case of a coolant system, unless there are problems with bubbles, the problem is with electrons.

The plan
The truck has a 150,000 miles on it, so I decided that I would do a small refresh. It might seem like I was throwing parts at it, but it was more that - with those miles - things are getting old. I didn't want to be going in-and-out and in-and-out.

My plan was:
  • Check the IPR connector/replace the wiring heat shield
  • Check/replace the IPR screen
  • Check the ICP connector
  • Replace the ICP
  • Check the up-pipe/downpipe connections
  • Replace the coolant and oil temp sensors
  • Replace the throttle pedal assembly

The task notes
I removed the batts, the CAI, intercooler piping, and top alt to get access to the turbo/ pipes/IPR. I do have to say that the oil cooler relocation adds some additional challenges for turbo access.

The IPR valve would not come out. I ended up breaking the connector off with a pair of channel-lock and using a closed end wrench to crack it loose. So... new IPR.

The IPR wiring - again - was dissolved just ahead of my last repair. I used extra wire heat shield after making the repair. That was likely the no-throttle response problem.

The exhaust leak ended up being the turbo itself - as near as I can figure. All of the band connections were solid and clean. I opted for a replacement turbo.

I found dissolved insulation in the coolant temp wire as it comes from the harness. I ended up replacing that wire segment and the parallel segment to the oil pressure switch. I covered both with wire heat shield. I did replace the coolant and oil temp sensors as planned. I figured that I might as well.

The throttle assembly is really simple to replace. It only takes a couple of minutes. The new firm pedal is nice, even if I am sure that the IPR wiring was the issue.

The results
Well... the truck started in about 1 second after the weeks of sitting. Always like that. ...and all of the problems appear to be solved:
  • No exhaust leak
  • Good turbo sound and VGT response
  • Tons of power like nothing that I have had before
  • No intermittent no-throttle response

So... to those of you with an intermittent no-throttle-response and no codes, you may want to look at the IPR wiring. Dig deep, make good repairs, and then use friction tape and wiring heat shield to protect it properly.

One additional point... I work on my truck alone. That makes the up-pipe/downpipe and serpentine belt removal/replacement extra special. I can't offer much help with the up-pipe/downpipe.

But... I can recommend that - to get the top alt off easily - use a 1/2" breaker bar with a hole through the end of the handle. You can take the tension off of the belt and then tie wrap the end of the breaker bar to a leaf spring/crossmember/anything convenient. Then get up top and slip the belt off of the alt and tie wrap it to one side. You can then get the alt off.

When you are done, put the belt back on the alt pulley and cut the tie wrap. Kinda obvious, but maybe not.



 
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Discussion Starter #2
Question related to the above...

Does anyone know what the head loss measured across a catalytic converter on a 6.0 should be? I asked the local muffler shop and they said that there is no way to check to see if a catalytic converter is clogged.

That seems a bit odd to me. I would think that a blower to provide the proper exhaust flow rate and two pressure sensors could answer that question. I'm open to anyone explaining to me why I'm wrong, though.
 

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Great that you got it solved.

If you tug on the serpentine belt, theres a clip on the tensioner pulley to lock the belt loose which allows 1 person removal.
 

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Discussion Starter #4
Great that you got it solved.

If you tug on the serpentine belt, theres a clip on the tensioner pulley to lock the belt loose which allows 1 person removal.
I'm glad that you mentioned that. When I did my relocation, I tried to use that clip but couldn't get it to engage. I didn't even try this time but never did try and figure out what I might have been doing wrong. Maybe this is the way for clip fails!
 

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Discussion Starter #5
Pics fixed.
 

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When you say throttle pedal, you mean the adjustable pedal assembly? AKA GAS PEDAL?

my brake pedal is loose as **** and can jiggle it around, im assuming this is not supposed to be like that? im having a random hesitation , similar to what youre talking about in this thread. its intermittent. So did you simply cut and splice new wiring and a connector to the IPR or just add the heat wrap?
 

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Discussion Starter #7
When you say throttle pedal, you mean the adjustable pedal assembly? AKA GAS PEDAL?
Yes. ...but no gas. :)

my brake pedal is loose as **** and can jiggle it around, im assuming this is not supposed to be like that?
I wouldn't think so. I've never replaced one.

im having a random hesitation , similar to what youre talking about in this thread. its intermittent. So did you simply cut and splice new wiring and a connector to the IPR or just add the heat wrap?
In my case, I had to actually cut into the injector harness back to near the secondary fuel filter to find the short. I then replaced those wire segments with new wire. ...and, then, secured it with heat wrap. I don't know that I ever replaced the connector. That wasn't the problem. The harness was the problem.
 
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I just deleted my CAT yesterday (210k miles and finally got around to doing it). Fuel economy had been steadily declining and it seemed that power was dropping a little also. When I removed the CAT, there was one clear pathway where I could see through it, but it was VERY small. I believe I had excessive pressure drop going through it.

All that said, there really isn't a way to determine the pressure drop through the CAT. You could drill holes in the exhaust (upstream and downstream of the CAT) and rig up a monometer, but it would be hard to get accurate data and probably not worth the effort. The only thing I know of is to remove the downpipe and run it to see if power and fuel economy increases (or remove the CAT).

Edit - I guess there is one more indicator - EGT. I really don't watch that close enough to know if there was any difference after the CAT was removed, but there pretty much has to be somewhat of a drop. I wish I had paid more attention to it!
 

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Discussion Starter #9
...

All that said, there really isn't a way to determine the pressure drop through the CAT. You could drill holes in the exhaust (upstream and downstream of the CAT) and rig up a monometer, but it would be hard to get accurate data and probably not worth the effort. The only thing I know of is to remove the downpipe and run it to see if power and fuel economy increases (or remove the CAT).

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That's what I had ended up concluding (the thread is a bit old now).

Since then... When anyone complains of low power and no codes with an existing cat, I have been recommending that they disconnect the downpipe form the inlet to the cat and pull the cat to the side with wire. Restored power = clogged cat. Not very scientific but not difficult, either.

Thanks, Mark!
 
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Oops. Sorry I didn't see the date on it - only a year old, lol!

Thanks for the gracious post above DJ!
 

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Why is everyone upset over "Old" threads. I was on a car forum before my 6.0 and everyone got butthurt if you posted new posts if there were old existing posts that answered the same questions. Wouldnt you want to revive the old thread instead of creating multiples of the same topic?
 

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I didn't think he was complaining at all, it was more of an fyi to me ..... and I admittedly wasn't paying attention to the full thread (happens a lot more than I would like to admit!!!).
 

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Discussion Starter #13
No complaints here. I was glad to have Mark chime in. He's a knowledgeable and respected resource.

My only issue with old threads is that I don't want people to spend their valuable time to help me through something that is mistakenly believed to be a current issue when it has been concluded for quite some time. There are new guys who need their time more.

It's easy to overlook posting dates. If I get the impression that someone has overlooked a long lapse, I'll point it out. If - after being made aware of the posting date - they still want to continue the convo, that's great.
 
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Gotcha, i just notice that a lot of people mention " old post" and it seems like its more frowned upon. all good, thanks for the clarification. I guess i try to always read the comments before posting anyway. ohwell
 

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Discussion Starter #15
Yes to a general frowning on old posts. It does sometimes seem knee-jerk. Like the vertical video complaint on other sites.

I've never been a mod. I do know that I've seen two rock solid mod old thread complaints:

#1) Sometimes people will jump around posting on old threads to raise their post-count - usually so that they can sell something.

#2) Sometimes people will post a related - but maybe not at all the same problem - on an existing resolved thread. A single no start thread with 5000 posts would be of no help to anyone.

Another issue with old threads - although maybe not as much of an issue as those first two - is they can have grossly incorrect info in them due to having been created at an earlier stage of group learning.

I can guarantee that we can find on here a thread supporting the use of Dorman oil coolers before everyone figured out that the green seals were crap. "So inexpensive. Easy install. Great warranty." There are some whopper early EGR cooler threads on here, too. If a new person runs across those resurrected threads thinking that it is good current state-of-the-art info, that's bad for everyone.

Beyond that, I agree with @Boudah 's earlier comment that adding to an existing *good* thread is a good thing.
 

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gotcha. btw, was your accelerator assembly "loose" like physically or what was actually replaced?
 

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Discussion Starter #17 (Edited)
gotcha. btw, was your accelerator assembly "loose" like physically or what was actually replaced?
I'm not sure that I understand the question, but I'll try to cover it in the answer...

My pedal was fine - not loose, but a little easy to push. The spring just wasn't as "springy" as the replacement. Of course, you can't know that until you replace it. I replaced it on principle because of the intermittent no throttle response problem and the related throttle codes. The problem was actually the IPR valve wiring (I am very sure), but I didn't regret replacing the pedal, at all.

The assembly itself was rock solidly mounted.

The replacement unit includes everything - pedal, arm, spring mechanism, and potentiometer. You just unplug the old, remove the fasteners, pull it, put the new one in place, reaffix, and plug in. It takes longer to get the tool.
 

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You answered it , thanks


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