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Thread: help with stumped fueling issue

  1. #1
    Senior Member JUSTASBC's Avatar
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    Default help with stumped fueling issue

    I have been having problems with my truck in my sig. I am currently running complete open loop. When I start it, it will run rich (13.5ish AFR) until it is warm. When the engine is warm I can drive it for a very long period of time without problems and my AFR will stay right around 14.6. If I park the truck even for 15 minutes it will run horribly lean (like around 19 AFR). Once it reaches this point I literally have to park it for about 5 hours for the problem to correct its self. I have adjusted everything that I can possibly think of without it working properly. Something that has me stumped is that I am not adding any fuel at all for warm up. I would think that it would get richer as it warms up, not leaner. In case anyone is wondering I have my IAT mounted in the cold side of my wet intercooler just under my radiator, and it is usually right around ambient temp. I have also mounted it in the back of the intake manifold with the same results. It seems as though I get this problem because my aluminum intake is warming up from the heads and transfering to the injectors, and lines. Any help would greatly be appreciated.
    Thanks,
    Daryl
    05 Joe Gibbs black RCSB ram air hood, Leer tonneau, blacked out tail and head lights. Forged 370, Eagle crank, Wiseco pistons, Compstar Rods, Pro Flo XT intake, KB Racing log, spool valve, T6 S480 1.32 A/R, boost activated cutout, TSP 2.5 5.3l heads, Comp Cam 224/230 .600 with rockers, comp cams 1.75 roller rockers, dual Walbro 450's, Injector Dynamics id1300's, 4l80e w/3200 multidisk Circle D, trutrac w/3.73's, 3"DI/DO Magnaflow, tips through the roll pan, running COS3 Semi OLSD OS#12592618

  2. #2
    Lifetime Member 5.7ute's Avatar
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    Have you tried adjusting the charge temperature blending factor?
    Log the charge temp that the pcm is using & see if this gives any insights.
    The Tremor at AIR

  3. #3
    Senior Member JUSTASBC's Avatar
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    The problem I am having is after the engine is warmed up. There will be nothing to adjust that I can think of. The ECT is up to temp and the IAT is working fine and the truck runs fine. When it sits for a period of time those values dont change at all and the truck runs horribly lean. The part that still baffles me is that when the intake warms up, the engine runs lean. I would think if anything it would run rich. Maybe I am overlooking something.
    05 Joe Gibbs black RCSB ram air hood, Leer tonneau, blacked out tail and head lights. Forged 370, Eagle crank, Wiseco pistons, Compstar Rods, Pro Flo XT intake, KB Racing log, spool valve, T6 S480 1.32 A/R, boost activated cutout, TSP 2.5 5.3l heads, Comp Cam 224/230 .600 with rockers, comp cams 1.75 roller rockers, dual Walbro 450's, Injector Dynamics id1300's, 4l80e w/3200 multidisk Circle D, trutrac w/3.73's, 3"DI/DO Magnaflow, tips through the roll pan, running COS3 Semi OLSD OS#12592618

  4. #4
    Joe (Moderator) joecar's Avatar
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    Log/tune files.

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    Fuel temperature will also affect this, I had this happen with a car I used to run a standalone on. I could make it less bad with tweaking IAT fueling adjustments. If you drive it for just 1 or 2 minutes, does it clear right up? For me, the IAT would drop slightly at that point but more importantly the fuel rail would have cooled by then. I noticed in stop and go traffic after a while the idle would begin to hunt between cells, acting kind of as if I'd shut it off for 15 minutes and come back. I never could quite find the right combination of weather conditions and motivation to finish hammering that one out.
    1998 GMC Sierra K1500 5.7/4L80E, longtubes, 411 w/COS 5, marine cam/intake, Whipple. 91 octane at 6000'.
    1997 GMC Sierra K3500 7.4/4L80E, 411 w/COS 3, Whipple, small cam.
    2004 Corvette Z06 with longtubes.

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    Senior Member JUSTASBC's Avatar
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    It was 77 degrees outside that day. The warm up was completely cold and warming up while idling. The warm was a short drive when the engine was completely warm. The 15 minute restart was after the warm drive, and 15 minutes in key off. I measured the intake with a infrared heat gun, and on the 15 min restsart the base bear the injectors was 158 degrees, and the intake plenum was 125 degrees. I am not sure how to correct this unless I move the IAT to the intake manifold, but then my temos will be abnormally high on restarts. I wish I could figure out a way to install a 2nd IAT sensor on the base of the runner, and to add fuel that way. Any help is apprecieated.

    Also this problem does not go away after a couple minutes, it will stay there until the engine cools down completely. I want to try this with an empty tank of gas, and fill it up with cool gas to see if this has any effect on it when I get some time (maybe tomorrow). One of the things I do think is a problem that I will be changing is my fuel pressure regulator. I have that mounted on the side of my intake, and when it is completely hot from the intake I will notice it down a couple lbs. This obviously doenst help the issue, but should not cause the drastic change I am seeing. I have even turned the pressure back up without a change, it is still very lean. I did buy phenolic board, and was going to have a machine shop machine off the base of the flange on the intake to try and eliminate the heat soak, but I cant find a machine shop that can hold on to the intake while machining.

    Just to add info, the IAT is mounted in the wet intercooler and just about under the radiator, so hot air is not running on it. The fuel system is a return style with a 450 LPH Walbro running all the time and another 450 LPH Walbro hooked to a hobbs switch.

    Something that really baffles me is that apparently the air is warmer than the PCM is assuming, but wouldnt that cause a rich condition, not lean condition? Im really stumped on this one.
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    05 Joe Gibbs black RCSB ram air hood, Leer tonneau, blacked out tail and head lights. Forged 370, Eagle crank, Wiseco pistons, Compstar Rods, Pro Flo XT intake, KB Racing log, spool valve, T6 S480 1.32 A/R, boost activated cutout, TSP 2.5 5.3l heads, Comp Cam 224/230 .600 with rockers, comp cams 1.75 roller rockers, dual Walbro 450's, Injector Dynamics id1300's, 4l80e w/3200 multidisk Circle D, trutrac w/3.73's, 3"DI/DO Magnaflow, tips through the roll pan, running COS3 Semi OLSD OS#12592618

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    Senior Member JUSTASBC's Avatar
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    Well after plenty of reading and testing I believe the heat soak on the injectors is causing the issue. Apparently Bosch put out some injectors that had this problem. Now I need to see how I can fix it. Has anyone else ever ran into this?
    05 Joe Gibbs black RCSB ram air hood, Leer tonneau, blacked out tail and head lights. Forged 370, Eagle crank, Wiseco pistons, Compstar Rods, Pro Flo XT intake, KB Racing log, spool valve, T6 S480 1.32 A/R, boost activated cutout, TSP 2.5 5.3l heads, Comp Cam 224/230 .600 with rockers, comp cams 1.75 roller rockers, dual Walbro 450's, Injector Dynamics id1300's, 4l80e w/3200 multidisk Circle D, trutrac w/3.73's, 3"DI/DO Magnaflow, tips through the roll pan, running COS3 Semi OLSD OS#12592618

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    I had your exact problem on my boosted TA in complete open loop MAF only tune....it was the charge temp blending table. When the engine was warm the car would lean itself way out. If I let it sit and cool down it would go back to normal. It would go LEAN when WARM and RICH when it was cold out, exact opposite of what I expected. I moved the charge temp blending table to something more ETC based than IAT based and the problem went away.

  9. #9
    Senior Member JUSTASBC's Avatar
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    I am actually finding out this is a problem with the injector. The injector is heatin up from the intake. The internals of the injector are expanding and physically changing the flow of the injector. There are a couple main fuel injector distributors out there that have discontinued selling these injectors because of this exact problem. Now if I can just get Bosch to stand behind their product. It really has me baffled, they must have noticed this in testing yet still shipped them out the door. There is no way you can run an engine with these injectors unless you always run with at least 2 tunes with you.
    05 Joe Gibbs black RCSB ram air hood, Leer tonneau, blacked out tail and head lights. Forged 370, Eagle crank, Wiseco pistons, Compstar Rods, Pro Flo XT intake, KB Racing log, spool valve, T6 S480 1.32 A/R, boost activated cutout, TSP 2.5 5.3l heads, Comp Cam 224/230 .600 with rockers, comp cams 1.75 roller rockers, dual Walbro 450's, Injector Dynamics id1300's, 4l80e w/3200 multidisk Circle D, trutrac w/3.73's, 3"DI/DO Magnaflow, tips through the roll pan, running COS3 Semi OLSD OS#12592618

  10. #10
    Senior Member JUSTASBC's Avatar
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    Just to update this thread, I have found out that the problem was indeed the injector heating up. I switched to id1300's, and the problem went away. Hopefully nobody else runs into this.
    05 Joe Gibbs black RCSB ram air hood, Leer tonneau, blacked out tail and head lights. Forged 370, Eagle crank, Wiseco pistons, Compstar Rods, Pro Flo XT intake, KB Racing log, spool valve, T6 S480 1.32 A/R, boost activated cutout, TSP 2.5 5.3l heads, Comp Cam 224/230 .600 with rockers, comp cams 1.75 roller rockers, dual Walbro 450's, Injector Dynamics id1300's, 4l80e w/3200 multidisk Circle D, trutrac w/3.73's, 3"DI/DO Magnaflow, tips through the roll pan, running COS3 Semi OLSD OS#12592618

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