possessed 5.3 swap.. help
Thread Starter
Teching In
Joined: Jan 2018
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possessed 5.3 swap.. help So, I need someone to talk me off the ledge with this thing. Running out of ideas
Truck is an 85 S-10, with a bone stock 100k mile 2000 5.3/4l60e swapped in. I did the harness per LT1swap.com, and Brendan did the tune. Has some goofy quirks, and is pig rich.
First issue- I cannot shake a P0121 code. Throttle body is spotless, brand new Napa TPS, checked ground, has 4.98 volts on ref wire, has continuity on the signal wire between the ecm and sensor plug. voltage at idle is .40, but only 2.93 at WOT. sensor will go to 9.95 off the throttle body manually cycling it. The wierd thing is my scanner will show 0% throttle and 100% at wot. Im not sure what to do with it. Did the relearn multiple times.
Second issue- Toss the truck in gear it will sit and idle, as soon as you touch the throttle it will try and spike to 1500-2000 rpm and stay there. Will run through town on its own at 40 mph with zero throttle input, and showing 0% on a scan tool. If you bump it into nuetral it will spike to 3000 rpm on its own. When you come to a complete stop it will finally idle down and sit there instead of trying to push through the brakes.
I've swapped MAF's, a TPS, a MAP sensor, everything but an entire throttle body at this point, cant find a vacuum leak, fuel pressure is a touch low (45-50 psi) but would that cause a bunch of this? Suggestions, thoughts, ideas?
Truck is an 85 S-10, with a bone stock 100k mile 2000 5.3/4l60e swapped in. I did the harness per LT1swap.com, and Brendan did the tune. Has some goofy quirks, and is pig rich.
First issue- I cannot shake a P0121 code. Throttle body is spotless, brand new Napa TPS, checked ground, has 4.98 volts on ref wire, has continuity on the signal wire between the ecm and sensor plug. voltage at idle is .40, but only 2.93 at WOT. sensor will go to 9.95 off the throttle body manually cycling it. The wierd thing is my scanner will show 0% throttle and 100% at wot. Im not sure what to do with it. Did the relearn multiple times.
Second issue- Toss the truck in gear it will sit and idle, as soon as you touch the throttle it will try and spike to 1500-2000 rpm and stay there. Will run through town on its own at 40 mph with zero throttle input, and showing 0% on a scan tool. If you bump it into nuetral it will spike to 3000 rpm on its own. When you come to a complete stop it will finally idle down and sit there instead of trying to push through the brakes.
I've swapped MAF's, a TPS, a MAP sensor, everything but an entire throttle body at this point, cant find a vacuum leak, fuel pressure is a touch low (45-50 psi) but would that cause a bunch of this? Suggestions, thoughts, ideas?
Thread Starter
Teching In
Joined: Jan 2018
Posts: 21
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swapped one, same. went as far as taking a complete throttle body with TPS/IAC off a buddy's well running LS swapped c1500, behaves the same. Thats why im leaning towards the tune being screwy but I cant prove it.
Check over the harness really good. Was the ecm matching to the original harness? Did brandon just remove vats and codes? Did he change anything else in the tune?
Try logging iac counts. Should be between 40-60. If they are way high or maxed at 300. Means iac is completely closed trying to reduce airflow without any luck. If this is the case, close throttle blade at idle via screw. Make sure there isnt a huge hole in blade allowing to much airflow. Also check blade for good movement and not being stuck.
Try logging iac counts. Should be between 40-60. If they are way high or maxed at 300. Means iac is completely closed trying to reduce airflow without any luck. If this is the case, close throttle blade at idle via screw. Make sure there isnt a huge hole in blade allowing to much airflow. Also check blade for good movement and not being stuck.
Thread Starter
Teching In
Joined: Jan 2018
Posts: 21
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Check over the harness really good. Was the ecm matching to the original harness? Did brandon just remove vats and codes? Did he change anything else in the tune?
Try logging iac counts. Should be between 40-60. If they are way high or maxed at 300. Means iac is completely closed trying to reduce airflow without any luck. If this is the case, close throttle blade at idle via screw. Make sure there isnt a huge hole in blade allowing to much airflow. Also check blade for good movement and not being stuck.
Try logging iac counts. Should be between 40-60. If they are way high or maxed at 300. Means iac is completely closed trying to reduce airflow without any luck. If this is the case, close throttle blade at idle via screw. Make sure there isnt a huge hole in blade allowing to much airflow. Also check blade for good movement and not being stuck.
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Thread Starter
Teching In
Joined: Jan 2018
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Tried that too, sprayed everything down, not even a hint of idle change. Disconnected the brake booster and plugged it, no change. Just seems odd to me that the only time it does it is if youre running down the road and bump it into nuetral it wants to rev up. Not doubting your theory at all, just confused about all of this. Ive been banging my head against the wall for days now.
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Verdad Gallardo Thread Starter
Teching In
Joined: Jan 2018
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Only thing i get for a check engine is a P0121, thats it. I did use new parts house gaskets as i did have the intake off. I sent Brendan a list of what i had (application, what motor was out of, what injectors and what i was doing) outside of that I have no idea what is actually in the ECM. Wouldnt a Hoaky intake gasket show up when i hosed it down? At this point im not against swapping intake gaskets if that will solve it but im trying to avoid throwing more parts/money at it until I have a direction. Only reason we swapped the parts we have already is I have a buddy with a known, functioning twin to this swap. Im super greatful for your help so far though. Im losing sleep over this stupid thing.
Thread Starter
Teching In
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only picture i have on my phone currently. The Ecm isnt mounted, but sits next to the brake master on the inner fender. you can see the harness ends. In this picture there isnt a PCV vent hose installed, but there is a hose there now.
Staging Lane
Joined: Oct 2014
Posts: 92
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I used Brendan's wiring guide and had him tweak the ecm .It works although it took awhile to sort out some details -the Vehicle Speed signal -brake signal and IACV counts .The launch tech easy diag 2.0 android software was the cheapest scanner I could find to view the IACV counts about $ 100.00 for the software and the connector .
In your case I would look at the O2 sensor readings and verify they are cycling and in range .
In your case I would look at the O2 sensor readings and verify they are cycling and in range .
Thread Starter
Teching In
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As far as I can tell with my scan tool/Ultra gauge is the o2's are cycling and reading, but i cant watch them on a graph. I have another set of intake gaskets on hand I'll probably swap in an attempt to eliminate the possibility of a vacuum leak. Would a incorrect VSS cause issues? It is reading but it isnt accurate because i had it programmed for the 3.73s in the 8.8 im building but havent swapped in. Currently has 3.08's
How did you say your PCV was set up? You mentioned a vent hose, but since you're not running a MAF it may be best to plug the TB and intake ports and just stick a vent on the valve cover until you figure this out.
Thread Starter
Teching In
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I am running a MAF, so the PCV is set up just like it would be in a stock silverado. My buddys swap who Ive been stealing parts from does not run a maf. Sorry for the confusion.