Ford Powerstroke Diesel Forum banner
1 - 4 of 4 Posts

·
Registered
Joined
·
29 Posts
Discussion Starter · #1 ·
Hi, I've been trying to figure out why my relatively new to me 2007 F350 has been blowing black smoke for about a year now. I've followed many recommendations from people here, and have never had any change in my symptoms, and have never had any engine codes. The truck will roll coal if I do anything other that completely baby it, but occasionally it will be a more wispy smoke. Often there will be a lighter continuous stream of smoke when cruising under load.

I noticed it only really smokes when the engine is warmed up, so I started trying to figure out why. I drove the truck while monitoring the temps and a bunch of other pids with ForScan. I noticed that the EGR is commanded to 0% when warming up, and starts opening almost exactly when the EOT reaches 150. From that point on, it is never commanded completely closed again. Usually it runs around 10% when idling or coasting, dipping a bit when gassing, then raising when releasing. I thought this was pretty suspicious, so I used ForScan to command the EGR valve to 0%, and it pretty much completely and instantly stopped smoking. It went from rolling coal almost every time I accelerate to usually not smoking at all, and maybe just a small puff that clears quickly when really giving it to her.

I took my truck to a mechanic a few weeks ago, and he thought there was a problem with the EGR valve too. He gave me a loaner valve to try and see if it helped, since OEM valves are backordered. I've been digging into it because I want to know what is going on, and generally like to do my own work when I can. This loaner valve is behaving just like my old valve was. Here is a chart of the desired EGR valve position (blue), and the actual position (red). I recorded the data in ForScan, but I'm plotting it in a spreadsheet since ForScan's plots are hard to read. Half way through, I used ForScan to command it to 0% (it still seems to compute the desired position, but the actual position stays at 0). While recording this data, I was just driving around the neighborhood giving it gas then coasting over and over.

Rectangle Slope Font Parallel Plot


It looks to me like the valve is doing a pretty good job of achieving the desired valve position. I have pulled both this and my original valve several times, and they have never been crusty - just a coating of soot that easily wipes off. I also tried just unplugging the EGR valve and driving around, which resulted in a bunch of codes and still lots of smoke. I have a bunch of other data from the above session (EOT, ECT, MAP, MAF, IAT, IAT2, EBP desired EBP actual, VGT%), but I have a hard time seeing any difference in any of it before and after setting the EGR valve closed, other than the MAF which higher when coasting / idling with the valve forced closed.

So, my questions are:
  • Does it look like this valve is misbehaving? Is it likely that I had two bad EGR valves?
  • Is it normal for the ECU to not command the valve all the way shut, even when accelerating?
  • Something else going on making the ECU think it needs to open the EGR valve?

Thanks!
 

·
Master Tech
Joined
·
544 Posts
If the truck smokes with the valve unplugged and it's not stuck open then it's not EGR. I do think the EGR is exacerbating the smoke concern. I would look elsewhere - pressure sensors, air intake/CAC leaks and or restrictions and fuel injection. You purchased the truck used... is it tuned?
 

·
Compression Ignition Addict
Joined
·
10,362 Posts
Here is a link to your earlier thread. Seemed like you had done quite a few troubleshooting things back then.


Seemed like an exhaust leak back then. Did that fix it for a while?
 

·
Registered
Joined
·
29 Posts
Discussion Starter · #4 ·
Hi FordDoctor, the truck has a light FICM tune, and I am currently using the "towing" tune on the edge cts (first step past trans only tune). It was behaving the same way before the FICM tune, and I have reverted the edge tune back to stock while testing and I have never seen any difference in the smoke.

Hi Bismic, I found a tear in the CAC boot last year, which I think was the cause of the massive billowing and low boost from stopped. I think I had an exhaust leak after taking the turbo out and cleaning it, but after redoing the connection I think it is fine. I found the exhaust manifolds had small leaks, but my mechanic thought it was not nearly enough to be a problem. I'm not sure about the hissing sound I noted toward the end of that thread - I don't hear that anymore. I did find that the exhaust down pipe connection in front of the cat wasn't very tight, so that might have been the source.

I tested the resistances of both my original EGR valve and the loaner. I might have the pin numbers backwards, but here's what I measured with the valves closed:
original:
BC: 0.98k
CD: 3.95k
BD: 4.16k

loaner:
BC: 1.3k
CD 4.18k
BD: 4.4k

The loaner values aren't in range, but are pretty close to what's in this 2004 pinpoint test (https://www.powerstroke.org/attachments/pinpoint-test-w-egr-system-diagnosis-pdf.639746/). This test for a 2005 has really wide resistance ranges, so I'm not sure it means anything (https://f01.justanswer.com/heavy_ch...65_2005_Ford_Pickup_F350_Super_Duty_p0405.pdf). The resistances on my original valve look pretty suspect to me, though.
 
1 - 4 of 4 Posts
Top