LLY: Bad FPR symptoms at idle

cstephens93

cstephens93

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Sometimes when I am sitting at idle, in gear or in park, I have started to notice what sounds and feels like a surge in RPMs or something. It feels as if my engine is pulsing slightly and I can actually feel a difference.

I pulled up RPM and desired RPM on my edge insight and I have noticed that at idle, my actual RPMs average between 675 and 680. Today, I noticed the pulsing and surge-like feeling again and saw that the RPMs at idle were jumping between 680 and 690-700. Spiking on the higher RPM level when I felt the surge.

Is this a sure sign of my FPR going bad?

My CP3 and regulator has 250,000 miles on it, never been replaced.

Now this surge feeling doesnt happen every time i drive, ive just noticed it happening the past week or so.

Whats annoying is Im dealing with a power steering or brake fluid leak right now as well with a whining sound when i turn or come to a cruising stop, but I have another thread made for that lol

All these little things are happening ever since I paid off the truck about 2 months ago lol
 
Chevy1925

Chevy1925

don't know sh!t about IFS
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cstephens93 said:
In what scenario? at idle or at WOT?
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Well think about that. If the issue is at idle and you suspect it's the fpr, wouldn't you want to log at idle when the issue happens? Not being a smart ass, just giving you a process of diagnoses
 
cstephens93

cstephens93

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Chevy1925 said:
Well think about that. If the issue is at idle and you suspect it's the fpr, wouldn't you want to log at idle when the issue happens? Not being a smart ass, just giving you a process of diagnoses
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This is true.

I will log that.

I havent noticed any real differences in my rail pressure aside from the normal 1kpa variation between the two
 
cstephens93

cstephens93

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Okay, was watching my rail pressure and the desired and actual were pretty close to each other, within 1kps

I watched a video on youtube of a duramax that was surging and it was surging way way more than mine sounds like it is, not even sure if i would say mine is surging after seeing that video.
 
Chevy1925

Chevy1925

don't know sh!t about IFS
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I'll bet the fpr is going. Had a truck that did just like yours is doing. You could log pulse width and see it going up and down like crazy when loping but the rail didn't fluctuate much at all. Changed the fpr and smooth as silk now. It was an lly as well.

I had a feeling you wouldn't see a change but wanted to make sure. Your description is all too close to the one I just did
 
cstephens93

cstephens93

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Chevy1925 said:
I'll bet the fpr is going. Had a truck that did just like yours is doing. You could log pulse width and see it going up and down like crazy when loping but the rail didn't fluctuate much at all. Changed the fpr and smooth as silk now. It was an lly as well.

I had a feeling you wouldn't see a change but wanted to make sure. Your description is all too close to the one I just did
Click to expand...

Thanks. Im guessing I should just try to find an LBZ CP3 w/regulator instead of another LLY regulator.

I'm not looking forward to swapping the cp3 at all...
 
Chevy1925

Chevy1925

don't know sh!t about IFS
Staff member
Oct 21, 2009
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cstephens93 said:
Thanks. Im guessing I should just try to find an LBZ CP3 w/regulator instead of another LLY regulator.



I'm not looking forward to swapping the cp3 at all...
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Only if you have the ability to have it tuned in properly. Otherwise you will get a lope worse than you have now lol
 
skintback

skintback

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I have 134k mile lbz pump that i just pulled out to rebuild the motor from a hole in the piston. Has had a lift pump on it since 50k miles when the second owner bought the truck held rail fine and idled fine

300 shipped and you ship me back the core if your interested
 
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