I looked at NoWake200's 04 LB7 this weekend, and first thing I noticed was it had what felt/sounded it was "stumbling" at idle (That's the best way I can describe it; It was a smooth idle, no surges, just not right). This was right after he pulled up, without shutting the truck down. When I went to log the balance rates, I noticed that while it was "stumbling", the balance rates where all at 0, like if it's over idle, and a few of them woudl occasionally blip to something other than 0 for a fraction of a second. After shutting the truck down and disconnecting his edge (it still did the same thing with edge disconnected, but not quite as much, possibly due to shutting it down), I got more balace rate data and found #7 is out of spec at idle and starts out of spec when put in drive, then slowly drops "into" spec (just under -6.. Barely). One other injector was questionable (#5 I think). Could this be the FPR casuing the odd idle, or possibly the bad injector? Anything else that should be checked (Fuel filter was changed recently).

I would say a definate FPR. Most 01's that I've seen have it, including my 01 that I sold. It got worse and worse, then I finally changed it. FPR was the culprit.

My 04 LB7 has a slight intermittent stumnle at idle. What is the FPR that you replaced to cure it?
Thanks, Russ

I would say a definate FPR. Most 01's that I've seen have it, including my 01 that I sold. It got worse and worse, then I finally changed it. FPR was the culprit.

X-3

My 04 LB7 has a slight intermittent stumnle at idle. What is the FPR that you replaced to cure it?
Thanks, Russ


Fuel Pressure Regulator ;)

Dave, thanks for meeting up with me this past weekend. What I did notice is the Opti-Lube did help with the idle. Did not add it this past fill up and noticed the engine running rough again.

I also notice while going about 50-60 MPH letting off the fuel and then getting back on it (not flooring it) a good size puff of black smoke comes out.

Also in the garage there is a black spot on the drywall for the start up. I do not know if this is also normal.

I am going to get her into the shop and let the pros look at it.

If it is the FPR would that give us a high balance rate on 7 and 5?

If it is the FPR would that give us a high balance rate on 7 and 5?

I'm not 100% sure, but I don't think so.

Dave,

Did you do any logging of the fuel pressure data? A bad regulator would put acutal rail pressure off of desired. Check your log files to see how closely actual follows desired.

Nick

During logging, the Desired FRP was at 4931Psi the whole time. Actual ranged from 4666 to 5185 (all at idle). Second log, desired was the same, actual varied from 4681 to 5454.

During logging, the Desired FRP was at 4931Psi the whole time. Actual ranged from 4666 to 5185 (all at idle). Second log, desired was the same, actual varied from 4681 to 5454.


i have a similar prob on mine. pretty sure its the FPR, but as of lately, that stumble you are describing has shown up as well. 2 stroke oil cured the surge at idle from the fpr, but it isn't making a difference in the stumble.

the stealth 2 has a desired and actual number readouts and they look very similar to what you described cougar. i dont know if that number is descriptive of the rail pressure or if im looking at something else.

checked the oil, no diesel in it. no white or gray smoke at idle or at speed. i dont know what else to check....

During logging, the Desired FRP was at 4931Psi the whole time. Actual ranged from 4666 to 5185 (all at idle). Second log, desired was the same, actual varied from 4681 to 5454.

Log the PID for the FRPCV amps.

See if the amps are steady or all over the place.

If the regulator amps are not happy then I would lean to the FRPCV, if the amps are fairly steady try raising the idle from 680 to 700 or 710 and see if that helps.

The AC/Defroster being on has been known to cause some idle characteristics to be other than they are.

;)

Let me know if you want to meet up again.

I think the AC may of been kicking on... but not 100% sure. :(

Let me know if you want to meet up again.

I think the AC may of been kicking on... but not 100% sure. :(

I'm game.... Let me know.

We can try again this coming weekend.