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Thread: 7427 install, first impressions

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    Fuel Injected! JeepsAndGuns's Avatar
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    7427 install, first impressions

    Well, yesterday I finally got brave enough to try the 7427 pcm. I wasnt brave enough to jump in feet first and go all out. So I spent a couple hours and built a adapter from the plug from a junk 7747 ecm and some spare pigtails from a 7427. That way if it ran bad, or needed lots of tuning, I could simply unplug it and plug back in my old 7747 and drive it when I needed.
    First lesson learned, dont get in a rush and install the eeprom in backwards! I bought the moates G1 adapter, and I was so used to pin 1 being at the handle end of my zif socket like I have on my 7747, I just threw it in the same way. Turns out, pin 1 goes in away from the handle on the G1.
    After I turned on the key, and the fuel pump never shut off, and I couldnt get aldl connection, I figured out the problem. I dont know if I corrupted the bin on the chip, but I didnt want to risk it. So I threw it back in the autoprom, erased it then re programmed it. I installed it and it works fine, so I didnt fry the eeprom.
    Started the datalog and went for a small test drive.
    After the drive, my first impression is wow. What a vast improvement. It idles smoother and better, acceration is smoother and more crisp, steady cruise is smoother, throttle response is better, and even decel is smoother and better. Light accel is better/smoother, wot accel is better/smoother. Even seems to have just a tiny bit more power. Seems pretty much all rpm ranges are better.
    All this from a mildly modded stock bin. I imported my timing table from my old 7747 tune, and then just did some smoothing of the fuel maps. I also followed the steps and disabled all the trans controlls and turned off all the trans trouble codes, also disabled egr and turned off that code.
    Going by the datalog, seems all cells from about map 50-20 I was rich, map 60-80 were pretty close, and map 90-100 was a touch lean. So just a few logs and tuning and I think it will be all set.

    Now for the one and only problem I am having---the knock sensor. I made a small jumper wire to go in the plug for the esc to connect the knock sensor to the correct input on the pcm (using the old esc signal wire) but I am getting the knock sensor or circuit error code. So the check engine light is staying on. Its the only error code I get.
    I looked up on advance autos website and looked up a 89 and a 95 chevy 1500. The knock sensor I am using is for the 89 350. When I look up the 95 1500 truck, it shows two knock sensors. One for a auto, one for a manual trans. The one it lists for the manual trans is the same part number of the one it lists for the 89 truck. The memcal I am using is of corse from a auto truck. So do I need to use the knock sensor it lists for the auto trans models? I'm thinking mabey the esc in the memcal is not seeing the knock sensor I am currently using.
    79 Jeep Cherokee, AMC 401, T-18 manual trans, hydroboost, 16197427 MPFI system---the toy

    93 Jeep YJ Wrangler, 4.0L, 5 speed, 8.8 rear, homebrew hub conversion and big brakes, hydroboost, 2.5in OME lift, 31x10.50's---the daily driver

    99 Jeep WJ Grand Cherokee limited, 4.0L, auto, 2wd, leather and power everything, 99% stock---the long distance highway ride.

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    RIP EagleMark's Avatar
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    Re: 7427 install, first impressions

    Subscribed since I am putting together a 427 for my sons IH Manual trans...

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
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    Super Moderator dave w's Avatar
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    Re: 7427 install, first impressions

    The knock sensor I use when I convert to a '427 is a Standard Ignition KS6. The KS6 measures about 4K ohms. Most likely the knock sensor your currently using is 100K ohms? Try installing a 4K resistor instead of the current knock sensor and see if the error goes away.

    Maybe you need to bypass the old ESC module mounted near the EGR valve?

    dave w

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    Fuel Injected! JeepsAndGuns's Avatar
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    Re: 7427 install, first impressions

    I have a custom install on a non chevy engine, no egr and the esc is on the firewall in my setup. But I unplugged it and installed a jumper wire between the pins in the plug to connect the knock sensor to the pcm. I will try a resistor like you mention, is it something common I can find at somewhere like radio shack? Do I just put it inline somewhere between the knock sensor and the pcm?

    I had a code pop up today while doing another datalog. I dont know/cant remember if it was there yesterday or not. But on the error code list in the datalog, I am getting a error next to 36 throttle kicker failure. What does that mean? I remember seeing paramiters in the bin about throttle kicker settings, but didnt really pay attention to them.
    79 Jeep Cherokee, AMC 401, T-18 manual trans, hydroboost, 16197427 MPFI system---the toy

    93 Jeep YJ Wrangler, 4.0L, 5 speed, 8.8 rear, homebrew hub conversion and big brakes, hydroboost, 2.5in OME lift, 31x10.50's---the daily driver

    99 Jeep WJ Grand Cherokee limited, 4.0L, auto, 2wd, leather and power everything, 99% stock---the long distance highway ride.

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    RIP EagleMark's Avatar
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    Re: 7427 install, first impressions

    Yes radio shack will have them, may need a couple depending on what sizes they have. Wire them in series (in line) to make 4K. Not parrellel (next to each other). I bought a BIG pack that has 100s of them for $5. and built VATS bypass plugs.

    Your overall first impression has got me excited to get the kids truck done!

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
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    Super Moderator Six_Shooter's Avatar
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    Re: 7427 install, first impressions

    Quote Originally Posted by EagleMark
    Yes radio shack will have them, may need a couple depending on what sizes they have. Wire them in series (in line) to make 4K. Not parrellel (next to each other). I bought a BIG pack that has 100s of them for $5. and built VATS bypass plugs.

    Your overall first impression has got me excited to get the kids truck done!
    I have to ask why wouldn't you use a parallel configuration to attain a 4K ohm resistance?

    The 4K resistance would be to ground with the knock sensor unplugged. This is just for testing, not a permanent solution.
    The man who says something is impossible, is usually interrupted by the man doing it.

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    Fuel Injected! gregs78cam's Avatar
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    Re: 7427 install, first impressions

    From what I have read, the auto trans vehicles were the first to use the '6395, '7427 PCMs due to E-trans control. The manual trans still used the '7747 for a few years. The '7427, 6395, and others use a different Knock sensor and the circuitry for that knock sensor is on the memcal, so there is no need for the separate ESC. I thought there was a way to use the old KS with the '7427 but i don't recall exactly how. The info is out there, you might search TGO in the TBI board. So yes easy way is to use the right KS for the Auto.
    1978 Camaro Type LT, 383, Dual TBI, '7427, 4L80E
    1981 Camaro Z-28 Clone, T-Tops, 350/TH350
    1981 Camaro Berlinetta, V-6, 3spd
    1974 Chevy/GMC Truck, '90 TBI 350, '7427, TH350, NP203, 6" lift, 35s

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    RIP EagleMark's Avatar
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    Re: 7427 install, first impressions

    Quote Originally Posted by Six_Shooter
    Quote Originally Posted by EagleMark
    Yes radio shack will have them, may need a couple depending on what sizes they have. Wire them in series (in line) to make 4K. Not parrellel (next to each other). I bought a BIG pack that has 100s of them for $5. and built VATS bypass plugs.

    Your overall first impression has got me excited to get the kids truck done!
    I have to ask why wouldn't you use a parallel configuration to attain a 4K ohm resistance?

    The 4K resistance would be to ground with the knock sensor unplugged. This is just for testing, not a permanent solution.
    Electricity takes the path of least resistence, ie it would all go through one resister in parellel. Next time you have resisters out try it. 1k and 1k in series is 2k. 1k and 1k in parellel is 1k.

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
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    Super Moderator Six_Shooter's Avatar
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    Re: 7427 install, first impressions

    Quote Originally Posted by EagleMark
    Quote Originally Posted by Six_Shooter
    Quote Originally Posted by EagleMark
    Yes radio shack will have them, may need a couple depending on what sizes they have. Wire them in series (in line) to make 4K. Not parrellel (next to each other). I bought a BIG pack that has 100s of them for $5. and built VATS bypass plugs.

    Your overall first impression has got me excited to get the kids truck done!
    I have to ask why wouldn't you use a parallel configuration to attain a 4K ohm resistance?

    The 4K resistance would be to ground with the knock sensor unplugged. This is just for testing, not a permanent solution.
    Electricity takes the path of least resistence, ie it would all go through one resister in parellel. Next time you have resisters out try it. 1k and 1k in series is 2k. 1k and 1k in parellel is 1k.
    You would think so, but that's not entirely the case in an instance like this. ;)

    Trust me, I've worked with resistors for many years. Some of the circuits I needed to trigger had an allowable tolerance of 10 ohms, and required some creative resistor combinations to get it sometimes.

    If you'd have seen some of the calculations I had to go through during my Automotive Electronic Accessory Tech training, it would blow you away. The sad part is I don't quite remember how to use Kirchoff's Voltage Law anymore. I need to go through that again.

    On the other hand, if you use two resistors of the same value in parallel the final resistance will always be half the original value. So there's no reason to never use resistors in parallel.
    The man who says something is impossible, is usually interrupted by the man doing it.

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    RIP EagleMark's Avatar
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    Re: 7427 install, first impressions

    Great! Now that I had it straight in my head it may not be the case always...

    I had followed on online write up to make a vats bypass and they showed and said it was OK to parallel and even showed a picture. So I added up 2 resistors parallel and FAIL! Measured them and it came out to the one resister. I then got 2 new resisters that added up to exact ohms needed in series and it was still the same amount.

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
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    Fuel Injected! JeepsAndGuns's Avatar
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    Re: 7427 install, first impressions

    Quote Originally Posted by Six_Shooter
    The 4K resistance would be to ground with the knock sensor unplugged. This is just for testing, not a permanent solution.
    Oh, I was thinking yall ment to put the resister between the pcm and my current knock sensor to make it work. I would rather just install the correct sensor.
    So with the parts stores showing two of them, one for auto, one for manual, with the manual one being the same part number as the one I am currently using, would I be correct in assuming I need the one they list for automatic?

    Also, what about this throttle kicker error code I am getting? I cant seem to find any info on it online
    79 Jeep Cherokee, AMC 401, T-18 manual trans, hydroboost, 16197427 MPFI system---the toy

    93 Jeep YJ Wrangler, 4.0L, 5 speed, 8.8 rear, homebrew hub conversion and big brakes, hydroboost, 2.5in OME lift, 31x10.50's---the daily driver

    99 Jeep WJ Grand Cherokee limited, 4.0L, auto, 2wd, leather and power everything, 99% stock---the long distance highway ride.

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    Super Moderator dave w's Avatar
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    Re: 7427 install, first impressions

    I use the Standard Ignition KS6 for an automatic transmission when doing the '427 PCM conversion. The parts stores are not able to look up the correct knock sensor after the '427 PCM conversion. The old ESC module needs to be completely removed from the old knock sensor circuit.

    There are four wires that go to the old ESC module:
    1. 12 volt with ignition switch in the on position. (Usually Pink wire with a Black Stripe)
    2. Ground. (Usually a Black wire with a White Stripe)
    3. Knock Sensor wire ~ from knock sensor to ESC Module. (color varies by model year)
    4. Knock Sensor wire ~ from ECM to ESC Module. (color varies by year)

    Solder together wires 3 and 4, and check with an ohm meter to make sure you have continuity from the ECM to the Knock Sensor.

    dave w

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    RIP EagleMark's Avatar
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    Re: 7427 install, first impressions

    Quote Originally Posted by dave w
    I use the Standard Ignition KS6 for an automatic transmission when doing the '427 PCM conversion. The parts stores are not able to look up the correct knock sensor after the '427 PCM conversion. The old ESC module needs to be completely removed from the old knock sensor circuit.

    There are four wires that go to the old ESC module:
    1. 12 volt with ignition switch in the on position. (Usually Pink wire with a Black Stripe)
    2. Ground. (Usually a Black wire with a White Stripe)
    3. Knock Sensor wire ~ from knock sensor to ESC Module. (color varies by model year)
    4. Knock Sensor wire ~ from ECM to ESC Module. (color varies by year)

    Solder together wires 3 and 4, and check with an ohm meter to make sure you have continuity from the ECM to the Knock Sensor.

    dave w
    That sir is excellent information that should be in your 427 conversion article!

    Maybe it is but I don't remember it...

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
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    Fuel Injected! JeepsAndGuns's Avatar
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    Re: 7427 install, first impressions

    Yes, the old esc will be completely removed from the system once I get some time. I plan on doing that when I do the ecm plug swap and get rid of my adapter harness I am using right now.
    The local parts stores done have that brand of knock sensor, is there a way to cross refrence that to another brand? The monkey behind the parts counter had no luck doing so.


    I did some google work on this throttle kicker failure code I am getting, and I had zero luck on finding anything. All I can find when I search throttle kicker is a bunch of stuff about carbs, when I search error code 36 I get a bunch of other error codes. And I see no pins labeled for a throttle kicker on the wiring diagrams. So for now I just turned off the error code so it doesnt come back on.
    79 Jeep Cherokee, AMC 401, T-18 manual trans, hydroboost, 16197427 MPFI system---the toy

    93 Jeep YJ Wrangler, 4.0L, 5 speed, 8.8 rear, homebrew hub conversion and big brakes, hydroboost, 2.5in OME lift, 31x10.50's---the daily driver

    99 Jeep WJ Grand Cherokee limited, 4.0L, auto, 2wd, leather and power everything, 99% stock---the long distance highway ride.

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    Super Moderator Six_Shooter's Avatar
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    Re: 7427 install, first impressions

    What makes you think it's a "throttle kicker" error?

    The most likely error is "4T60-E Shifting Error" which would be reflective of the code you're running.
    The man who says something is impossible, is usually interrupted by the man doing it.

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