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Thread: 77 C10 5.3 swap running really bad.

  1. #1
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    77 C10 5.3 swap running really bad.

    Hi, I'm new to HP Tuners. I'm working on a 77 C10 with a 5.3 swap, trans is a 700R4. Working on adjusting the trans cable, but in the mean time, I can do 1 pull on the truck, and after that 1 pull, it feels like the engine bogs bad!. Maf disabled, SD only. STFT and LTFT disabled, 02 sensors unplugged. Wondering if anyone here has a similar setup and problem. Thanks in advance.

  2. #2
    Tuning Addict 5FDP's Avatar
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    You still need the front o2 sensors active.
    2016 Silverado CCSB 5.3/6L80e, not as slow but still heavy.

    If you don't post your tune and logs when you have questions you aren't helping yourself.

  3. #3
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    I want to tune this car open loop only. It's a summer vehicle. It doesn't get driven often. Do I need to have it set close loop for the ecm to run properly? Or does HP Tuners not work open loop only?

  4. #4
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    My guess is your first pull the engine is still cold and running off a richer afr from a fuel multiplier table. Your second pull is warm with with no multiplier and to lean. But you have provided no log or file.

    HPT can do an open loop tune, but why? You have not described any modifications that would require or benefit from a open loop tune. Adding the 02 sensors will make it run better through all conditions. If this is the route you still want to go you will need a wideband 02 sensor to tune with.
    Last edited by mecanicman; 11-22-2015 at 09:47 AM.

  5. #5
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    The truck belongs to a friend. He bought someone else's project. We thought the swap was done right at first, but noticed little by little that the engine harness is a hack job. One of the o2 sensors was not reading, we also had to add an obd2 port, because it didn't have one.

  6. #6
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    He wants to have it running the best possible, it doesn't have to be perfect. We don't need to hit 14.7 afr all the time under a low load. That's why he wants to go the open loop route. He doesn't want to put more money and time. He just wants to cruise it. I have the cold compensations done, both coolant and iat. Thanks.

  7. #7
    Tuning Addict 5FDP's Avatar
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    Well for it to run smoothly all the time and easier, having those o2 sensors installed will make life a breeze.
    2016 Silverado CCSB 5.3/6L80e, not as slow but still heavy.

    If you don't post your tune and logs when you have questions you aren't helping yourself.

  8. #8
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    If you want to disable all the things the PCM is good at controlling, run open loop and a 700R4, just throw a carb on it and a MSD box for the spark.

  9. #9
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    I don't want to disable everything the pcm does, if I did, I would say convert it to carburetor. The o2 sensors are not the only thing the pcm controls, it is just one of many things the pcm does.

  10. #10
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    I have tuned many setups on open loop. They run smooth, and afrs are good, not perfect, but good. Like I posted, the truck is a 77, it gets driven summer only. The fact that the truck has a lot of issues, I'm just trying to make it run descent. Once the truck gets running, the owner wants to do a complete new harness. I appreciate the advice, I would suggest he redo the whole setup first, but it's not my vehicle. Any input on how hp tuners functions on open loop only, would be greatly appreciated.

  11. #11
    You shouldnt have too big of a deal running it in open loop. If you have the MAF unplugged that insures you are in open loop. Like mecanicman suggested if it changes from the first run to the second its probably warming up and no longer using certain adders causing it to run lean. You need to stick a wideband on it and adjust the VE and I bet it will come right in line.
    1999 s10 blazer trailblazer edition nv3500 swap
    2006 GMC ccsb 4x4 duramax/allison

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    Quote Originally Posted by thething96 View Post
    I have tuned many setups on open loop. They run smooth, and afrs are good, not perfect, but good. Like I posted, the truck is a 77, it gets driven summer only. The fact that the truck has a lot of issues, I'm just trying to make it run descent. Once the truck gets running, the owner wants to do a complete new harness. I appreciate the advice, I would suggest he redo the whole setup first, but it's not my vehicle. Any input on how hp tuners functions on open loop only, would be greatly appreciated.
    I don't cosign with taking short cuts but if you must, get a wide band or use a wideband. Or else it will just keep dumping fuel. Then you will have more problems to deal with.

    Quote Originally Posted by 98vortecSilverado View Post
    You shouldnt have too big of a deal running it in open loop. If you have the MAF unplugged that insures you are in open loop. Like mecanicman suggested if it changes from the first run to the second its probably warming up and no longer using certain adders causing it to run lean. You need to stick a wideband on it and adjust the VE and I bet it will come right in line.
    Not quite sir.
    Last edited by POWERZONE; 11-23-2015 at 12:42 PM.
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  13. #13
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    Quote Originally Posted by thething96 View Post
    I want to tune this car open loop only. It's a summer vehicle. It doesn't get driven often. Do I need to have it set close loop for the ecm to run properly? Or does HP Tuners not work open loop only?
    Quote Originally Posted by thething96 View Post
    I have tuned many setups on open loop.
    I just went back and read what you said, these statements are contradictory.

    Explain how did you tune those other many setups in open loop?
    Last edited by POWERZONE; 11-23-2015 at 12:43 PM.
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  14. #14
    You're right POWERZONE I forgot its possible to run closed loop SD. I have to say though the OP says he's new to HP tuners, maybe thats why he's not sure how to force open loop on his tune, when he's tuned numerous setups in open loop.
    Last edited by 98vortecSilverado; 11-23-2015 at 12:49 PM.
    1999 s10 blazer trailblazer edition nv3500 swap
    2006 GMC ccsb 4x4 duramax/allison

  15. #15
    Just slap a carb on top if your not worried about it.

  16. #16
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    Yeah, I have tuned other setups, but not hp tuners. I didn't clarify that. But I am new to hp tuners. Its a great program. I do have maf plugged, but disabled. I didn't want to loose the iat reading on the maf.

  17. #17
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    The car pulls good for about a minute, even after warm up, but then it hesitates. My original intention was to see if anyone had feedback on similar setups. I'll keep on trying different things on this truck. I appreciate all the input from everyone. Thanks.

  18. #18
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    Just a quick update. We changed the fpr, the original one was holding 40 psi. I also disabled STFT and LTFT. Maf disabled, SD tuning only. Truck runs way better, just after a quick flash. The o2 sensors were making the truck run like sh1t, even after disabling them, maybe I was supposed to do something else to be completely on open loop. Will continue to post updates, hopefully this will help someone else. Thanks everybody for your input.

  19. #19
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    The truck's all done. Open loop tuning was very easy. Hp tuners is very constant when it comes to fuel values. The truck runs 14.5-15.4 afr on idle and very small load, 13.5-14.5 mid load, 12.5-13.0 on high load. Runs super smooth and idles good. Thanks again.

  20. #20
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    Any chance you'd be willing to share the tune you're working off of? I have a buddy who wants to use a 2001 5.3 in front of his 700r4 but I have no idea where to start on the tune.