Engine Rebuilding options for S/C

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So here is what is happening right now:

* start truck, slight stumble
* in reverse, foot on brake idling, I feel big bumps in engine rotation
* in reverse, lifting foot off brake, more big bumps in rotation. At least one cylinder definitely feels like its missing
* in drive, foot on brake, no bumping/missing
* in drive, foot off brake (no skinny pedal), doesn't feel smooth but there no big bumping
* in drive, accelerating, feels fine
* in drive, coming to a stop, feels rough for a second then smooths out
* in drive, accelerating a second time after a hard u turn, motor rough.
* in park, motor very rough but consistent, it's not trying to stall
* slip into park, motor evens out
* in drive, standing brake, a little skinny pedal motor gets really rough
* in reverse, standing brake, a little skinny pedal motor is noticeably worse then in drive
 
landtank said:
It might very well be the harness

try moving the harness around where it comes of the firewall and heads down to the engine while idling.
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Holy fxxxing hell!!!!!

It's my harness!

From the firewall I moved the harness all over with zero change. I looked over at the thermally wrapped section of the harness by the EGR valve. Shoved a golf club handle under it and just moved the harness up and the idle totally smoother out. I gave it one big push up and it's idling great. Just took it for a drive and its running perfect. I mean really perfect.

Rick you rule!

I'm going to inspect the harness I have. Either use it or get a new one from CDAN. I can do the connector extension for the SC throttle body while I'm at it.

Damn this sucks but its good news!

image-2106452541.webp
 
Is the harness a common problem? It would have been my last guess. When anyone does a rebuild should this be a standard item to be replaced as they are nearly 20 year old vehicles?

Thanks
 
sknyfrnchguy said:
Is the harness a common problem? It would have been my last guess. When anyone does a rebuild should this be a standard item to be replaced as they are nearly 20 year old vehicles?
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Its common knowledge that the EGR valve damages the harness. My harness was fine before my motor rebuild which is why I opted not to replace the harness. Now I am kicking myself for not replacing it. As for it being a PM item, I dunno. Hindsight says yes so :meh:
 
So now next question...

Since the SC will be going on and since the pump is now a Supra pump what about the FPR (fuel pressure regulator)? Which FPR is the one to go with? I've been reading that the OEM is a rising rate FPR and may be fine for my modest SC install. But it seems some opt for an adjustable FPR. Then do you piggy back it to the OEM one or does it replace it? I'm looking at this one currently: http://www.speedwaymotors.com/Aeromo...-PSI,9121.html
 
Yep, stock supra fpr is rising rate, and they run about the same base fuel pressure we run. Shouldn't be a problem. Supra pump if I remember right flows the same as the LC or very close to the same at the low voltage setting.
 
scottryana said:
Yep, stock supra fpr is rising rate, and they run about the same base fuel pressure we run. Shouldn't be a problem. Supra pump if I remember right flows the same as the LC or very close to the same at the low voltage setting.
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I think the reason why I am concerned is because the new Supra fuel pump definitely gets an increase of voltage as the fuel demand goes up. You can hear it in the pump. At WOT its really spinning. If the stock FPR can handle it, even at WOT, then I'm golden.
 
Yes but your engine is using a lot more fuel at WOT, usually it is at idle that the FPR is over run, because some pumps try to flow a constant amount and at idle there is very little demand at the engine so the amount the FPR has to bypass is high. Since the Supra pump flows less at low voltage and it is close to LC flow you won't have that issue. Hope that makes sense.
 
landtank said:
The LC has a rising rate FPR as well. I'm not saying that this is a problem, just that I haven't seen anything to require it on a Standard SC install.

Just bringing up the negatives of having an oversized pump should you have problems down the line.
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Duly noted and quoted for posterity ;)

I'm sure there will be plenty of "I told you so" coming my way in the future :bang:
 
Just ordered the engine harness from CDAN. Only three left in the U.S. and I have one of them coming my way next week sometime. $475 for the whole thing. Get em while they're hot!
 
I just talked to CDan today. Maybe I should have ordered one of the other two...
 
NLXTACY said:
Its common knowledge that the EGR valve damages the harness. My harness was fine before my motor rebuild which is why I opted not to replace the harness. Now I am kicking myself for not replacing it. As for it being a PM item, I dunno. Hindsight says yes so :meh:
Click to expand...

it's not the valve, it's the EGR pipe that gets so damn hot and is very close to the harness

so, to prevent melting of the harness and wire insulation, we wrapped the harness in heat resistant foil and zip-tied it away from the EGR pipe - not complicated to do
 
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