Aggravating problems with my rebuilt LS V6

heyjewel

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So the engine we rebuilt runs great. No fluid leaks. Clean exhaust. Clean oil and cooling system fluid. Some may remember I had some start then stall issues which I finally fixed with a fuel pressure sensor. A used one since new ones are gone with the wind. Now I have an issue with P0401 - insufficient EGR flow. I've been attacking this for several hours over several days - when I have time. Cleaned the EGR and ports thoroughly. There was nothing there anyway. Cleaned the IAC and ports. Nothing there either. Engine is clean. DPFE has been swapped twice. EGR vacuum acts same as my running V6. Applying vacuum to the EGR itself causes car to stumble but not stall. Same with the running car. I think there may be an exhaust leak but finding one is proving almost impossible. I need some way that such a leak will how up. Saw a scotty kilmer recommendation to get a $100 smoke machine and stick smoke hose in the exhaust pipe, plug the pipe and see where it comes out. Not ready to go that route yet.

So I'm wondering if there are any suggestions - either for things I'm overlooking for P0401 (I have looked at all the posts a search returned on here) or for locating an exhaust leak?

Thanks.

More non-engine problems to follow like my drivers seat set position usually does not work.
 
Have you tried activating the EGR valve with a scan tool while the engine is running (to see if you get the expected stumble, and to see what flow rate it reads)? That would verify the solenoid vacuum valve as well at the EGR valve (that you have already verified).
 
Have you tried activating the EGR valve with a scan tool while the engine is running (to see if you get the expected stumble, and to see what flow rate it reads)? That would verify the solenoid vacuum valve as well at the EGR valve (that you have already verified).

In fact today I was going to ground the signal to the solenoid to see if that activates the EGR. I dont think my little scan tool OR Forscan has that ability. Will check. Thanks
 
Hi George, mine was getting a similar code a few years back and it turned out to be just a broken wire in the hard to reach harness back in that area. That was after I did the differential pressure sensor replacement, as well as anything EGR-related. It was a simple fix, except for the access to do the repair. That harness seemed to have a kink in it where the wire broke.
 
Hi George, mine was getting a similar code a few years back and it turned out to be just a broken wire in the hard to reach harness back in that area. That was after I did the differential pressure sensor replacement, as well as anything EGR-related. It was a simple fix, except for the access to do the repair. That harness seemed to have a kink in it where the wire broke.

I am STILL fighting this P0401 problem. Grrrrrrrrr. I didn't want to but I finally broke down and bought the three parts that have to do with this DTC- the DPFE thing that supposedly fails a lot, the egr actuator solenoid and a Motorcraft EGR valve; NO HELP. I am now going to use the DVD step-by-step approach to see if I can find a missing voltage or broken wire or SOMETHING. Thing is with Forscan I seem to be able to read all the relevant signals which says the wires are OK.
I've got a brand new EGR pipe on the exhaust manifold AND brand new EGR hoses too. So I'm assuming that the passages in those are clean and clear. May just try to run a wire thru there to make sure.
I wish I knew exactly what passages there are in the intake manifold. Anyone got an inside view? I cleaned out all the passages I can get to around the EGR and NO HELP. But I wonder if there's some junk way in there needs cleaning?
I'm also going to put in a different Fuel Pressure sensor. Reason is that the fuel rail pressure is only 2/3 of what spec says - 19-20psi rather than 30psi. My grey LS daily driver has 29-30 psi. Wanna see if I get 30 in my red one when swapped. Can't hurt. Well except my hands which get all scratched up working back there. Strange maybe that there's no DTC for this?
 
Hi George,

Did you verify that pressure with a mechanical gauge on the shrader valve port?

The new egr hoses that you refer to, are they the ones that connect the pipe ports to the differential pressure sensor? Or are you speaking of the hard plastic vacuum hoses?
 
Hi George,

Did you verify that pressure with a mechanical gauge on the shrader valve port?

The new egr hoses that you refer to, are they the ones that connect the pipe ports to the differential pressure sensor? Or are you speaking of the hard plastic vacuum hoses?

Yes. The schrader reads 20psi on mech gauge.

Yes, they're the short hoses that connect dpfe to the 2 ports on the EGR tube. One possible fix for this says the hoses may be connected backwards. But they cant be caus they're different inside diameters.
 
I guess you would have to temporarily mount differential pressure gauges on each of the lines and drive it while noting their readings, to see if it is legitimate. Too bad that system check cannot be tuned out of the PCM, especially if the egr system is performing as expected but being called out incorrectly.
 
I guess you would have to temporarily mount differential pressure gauges on each of the lines and drive it while noting their readings, to see if it is legitimate. Too bad that system check cannot be tuned out of the PCM, especially if the egr system is performing as expected but being called out incorrectly.
Not a bad idea.
Ooooh that second thing is sorta illegal isn't it?
 
I just wanna wrap this thread up, even at the cost of some embarrassment to yours truly. A few posts up I opined that since the DPFE hoses were different IDs they would be highly unlikely to be on the wrong nipples. Well I'll be gobsmacked but that's exactly what I did a couple months ago apparently. I've been messing with the dpfe and always making sure I put the hoses on correctly. But never until Saturday last did I take a good look at the hoses at the pipe and there was my problem. Fixed the P0401. At least I persisted until this was fixed - and you guys did too, thanks.
But then I got a P0402! Fun, huh? This was due to a vacuum hose coming in contact with that EGR pipe and melting. I tried to patch it but that did not work so I found a new vacuum line at the local pick and pull. Fixed P0402 and several P030x indicating misses. Didn't know low vacuum could case missing but do now.
So I took her out for a hard 40-50 mile drive and all systems were go. Until I pulled into garage. First checked all DTCs and they were gone with the wind. Then looked under the hood and found a degas bottle seemingly bursting at the seams it was so full. Shortly thereafter it piddled on the floor. Continued in a cooling system thread I just opened.
 

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