16197427 idle issues - motor idles high when rolling forward

Hello everyone,

I've been a long time lurker of this site but this is finally my first post. The information on this site is awesome and has been a huge help to me. I guess I should start with some background info first.

I have a 1977 Chevy K10 with a 383 stroker, 10:1 compression, with a decently sized cam, and a manual transmission. It started off with a 670 Truck avenger carb but I was sick of constantly tearing it apart. My buddy had done a TBI swap on his CJ5 with a 304 in it and things went pretty smoothly for him so i decide why not try it. I swapped in a 1227747 ECM with a 350 throttle body, modified the AFPR to 15 psi, and upgraded to a high pressure fuel pump. Everything went really well and i soon had a reliable running motor.

This is where things started getting tougher. I had a pretty decent tune but could never get things where I wanted them. I couldn't ever get a good idle with closed loop so I had to force it to open loop. The idle was stable in open loop but was always way too rich. Everything I tried wouldn't lean it out enough.
At the time I was scouring the internet for answers but couldn't find anything. So I just ran the tune how it was and called it a day. Sometime later I found out about the 16197427 swap and everything about it sounded awesome. I picked up the parts i needed and swapped everything over.

I started with a 7.4L $0E BMHK BIN and changed all the parameters to fit my motor. I changed by VE Tables drastically and as of right now seem to have a pretty good tune. It is way faster and smoother than the 7747 ECM ever was and just cruises down the freeway at 70.

This finally leads me into my problem, which really is more of just an annoyance. My motor idle at 800 rpm while the truck is stopped but the second I start rolling the rpm jumps up to 1000/1200 rpm. Sometimes it blips from 1000-1200 rpm. It only return to 800 rpm when I'm fully stopped. This might be to help shifting for the manual transmission but it gets a little annoying when you're rolling up to a stoplight with your motor idling up and bouncing around. Does anyone know how to changed these setting or mess with this on the 16197427.

Sorry for the extremely long drawn out post, just thought a little background might help. Let me know if anyone has any questions or needs me to post my tune or data log. Also I am running a VSS.

Thanks

I have an auto so some things are different than yours but I have looked at the stock version of your bin. Have a look at
max mph and tps for idle spark
main and idle spark tables
main and idle ve tables
have you completely dealt with egr
I got rid of all throttle following and stall saver and put strong limits on spark retard.
I have no idea where this last comes from but when I move past 2 mph I am commanded and receive 33 extra rpm.

Thanks for responding.

I've played around with the the Idle parameters a bit and it seemed to help but didn't get rid of it completely.

I haven't changed the Max MPH/TPS for the idle spark in the idle spark advance folder but I did change it in the idle parameters folder. The .xdf I'm using has that parameter in two locations.

I have the following set:
Max MPH for idle VE - 20 (Set it to 20 because it seemed liked the lower values didn't do anything)
Max MPH for idle spark table - 20
Max TPS for idle ve - 3.1

I'll try changing the Idle Spark advance values and see if that makes a difference

I have everything for the EGR/spark retard/knock sensor turned off.

Also, i attached a copy of my BIN file if you want to take a look

I just had a quick peek at your bin. Your spark switch over is 3 mph and 1.6 tps. Also your AC idle values are 1000 rpm. I have a project comng up that is a manual and will be using the same bin as your original for my starting point. If you want you can pm me. I will do a compare between my dd bin and yours.

Quote:

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Originally Posted by myburb

I just had a quick peek at your bin. Your spark switch over is 3 mph and 1.6 tps. Also your AC idle values are 1000 rpm. I have a project comng up that is a manual and will be using the same bin as your original for my starting point. If you want you can pm me. I will do a compare between my dd bin and yours.

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I would start with an $OD 350 bin like BJYN, switch the trans settings for manual trans. Then find a 4.3 Manual bin and use the IAC throttle follower values.

When I set up this bin I used the same spark table in both idle and off idle so even if it switches over it should still use the same values. I run a york air compressor for airing up my tires on the trail so I increased the values on the AC idle table to help air up quicker. That would be awesome if you would compare my BIN to yours, I will send you a pm.

Fast355, I tried running a couple auto bins, I think they were BJYL and BJYM, but i kept getting really weird spark advance numbers. It would idle at the right part of the spark table but as soon as i revved the motor and let the rpm fall back down to idle the values would max out at some ridiculous number like 3000 degrees of advance, which isn't good. I'm not running a knock sensor so I think when I swapped over from 7747 to 7427 the knock sensor wiring might be different than what the new computer wants. I bypassed the knock sensor in the 7747 by giving it 5 volts and never had an issue. I think the 7427 is looking for a different voltage range for the knock sensor to show everything is okay.

What's really weird is the first time I tried the $0E BMHK it never had any spark issues, so I just disabled all the knock sensor and spark retard limits.

I would recommend ditching BMHK and going to a $0D bin as well. I started out with BMHK and I chased around various issues for a long long time before I switched over. I ended up using BJYM, which is a 5.7L auto bin, and just changed the spark and fuel to match what I was using. I have made many changes to it, but in the end it was way better than BMHK. I would recommend starting anew. I'm sure you could do a little searching on this site for my name and BMHK and find some of my troubles.
I am running mine on a AMC 401 with a manual trans.

JeepsandGuns, funny enough I actually read through a couple of your threads but by the time I found them I had already put a bunch of time into the BMHK BIN. After I read your threads I tried changing to $0D BJYM but I had some weird issues I couldn't figure out. I ended up going back to BMHK.
I've been exchanging emails with myburb and we tried tracking down the issues with little luck. We're gonna try starting with another $0E BIN and see what happens. The BIN were trying out is BDCH

I fixed my idle issues with a new timing chain....mines was stretched a good bit. I couldn't tell with the carb I had. The other issue I had was exhaust leaks. I had one by the O2 sensor and one a little after. These made my setup run richer too and had it constantly with big swings in fueling going from way rich to lean.

Quote:

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Originally Posted by g_chaps

I tried changing to $0D BJYM but I had some weird issues I couldn't figure out.

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What issues were you having?

Sorry for the delayed response, I was out of town for awhile.

The truck seemed to idle okay with the $0D BIN but as soon as you would hit the throttle it would fall on its face and the spark advance would jump all over the place. When I was watching the spark advance gauge in Tunerpro the numbers would max out to 50 degrees but if I watched the spark advance graph it would reach something like 2000 degrees of advance. It only reached 2000 degrees after you would let off the throttle and let the rpms return to 800, as soon as the rpms were steady at 800 the advance would look normal again. I switched over to $0E and never had that problem again.

Weird spark data in tunerpro sounds like you have the wrong adx file loaded. A decent build with a cam and heads will require more AE than stock. What size injectors are you running?

Could be that I had the wrong adx file loaded. I can always give it another shot and see what happens. When I tried the BJYM BIN I tried adjusting the AE tables but it didn't do anything which lead me to believe it was spark related. I'm running the 61.2 pph injectors at 15 psi. I've tried running big block injectors, 75.5 pph, running the 61.2 pph at 30 psi, but it was too hard to control overfueling at idle.

Small update on trying out the BDCH BIN.
The idle on this BIN is sooo much smoother than the BMHK. It's the first time I've ever had a smooth closed loop idle and the BLM's sit right at 128 at 800 rpm. I noticed that the BIN asks for a slightly richer commanded AFR at idle than the other BIN, its 13.9 instead of 14.7. As for the idling up as soon as I start moving, it still does it but it's not as extreme as the BMHK. Overall the BIN is much smoother than the BMHK. I still have to adjust my VE tables a bit because some of the values are a little off from switching over to BDCH.