High idle speed

Whenever I'm driving around and I pull out of gear or disengage the clutch, it seems like it takes forever for the idle to settle down from around 2Kish RPM down to around 1Kish.

I tried to fix this with some stuff I read about from RBob's notes on IAC logic "To reduce flair-up on engine start:

Lower the park position @ 0x5C2.
Lower the park to run delay @ 0x5C3.
Lower the kickdown time delay @ 0x5D7.
Lower the coolant vs. position values @ 0x5F5.


To quicken the return to idle after throttle blip:

Set delay @ 0x5E7 to 0.
Increase filter coefficient at 0x5E4.
Reduce throttle follower percentage @ 0x5F0 & 0x5F1."


Not sure if it helped really though....

Here is the original thread http://www.thirdgen.org/techboard/di...-follower.html from the prom tuning guidebook on TGO



What do I need to do to fix this?

'747 $42 L05......

Is the motor stock?

Could be a mechanical issue as well.

Not stock at all. Nothing wild either.

mildly cammed, ported and polished 193 heads, high volume oil pump, ported-enlarged-and-relieved oil return holes in lifter valley, Ultimate TBI, TB spacer, pod spacer, midlength headers, dual 3" exhaust with H pipe and turbo style mufflers. I think that's about all.

Not sure what kind of mechanical issue it could be, everything seems pretty solid with it.

I think it's my tune being so rough maybe?.. my tune is still pretty close to stock, which likely needs much more tweaking from the changes I made to the engine over stock.

Quote:

---

Not sure what kind of mechanical issue it could be, everything seems pretty solid with it.

---

Vacuum leak?

Got a log that starts with engine totallyu warmed up and all things in XDF turned off for data logging?

Here is a log I did today.

I don't see any vacuum leaks

Dual 3" exhaust!!!?
Have you checked your brake booster for Vacuum leaks?

Yeah, 2.5" would have been plenty I'm sure, but I figured if I do any kind of upgrades down the line (forced induction and/or bigger displacement engine) then the 3" pipes would be nice to have.

Sorry we posted at the samentime...Brake booster. Your low end must suffer pretty badly.

Yeah I'm pretty sure the brake booster is ok but how would you check it?

Actually the low end is excellent, like just about any TBI.. Amazing low speed torque, crisp throttle response and good fuel mileage, (for a pushrod V8 based on 1955 SBC architecture.)

I think having the H pipe really helps out with the low end and just all around power in general, the 3" pipes are about as big as I could have gone probably, any bigger would have been TOO big.

But no, the low end is spectacular, with no shortage of stump pulling torque. I can leave pretty hard in 1st gear and still chirp the tires all the way through 5th gear. Never been able to chirp it in 6th but by the time I hit 6th gear I'm already going 70+ MPH

If you have access to a smoke machine, fill it with smoke through the vac line hole, and see if any escapes.

I remember back in my early days when I was still running the 7747. I had a simmilar issue with the idle hanging like that, most noticeable at warm startup. I tried a few difffrent things before I got curious and changed a parameter called "IAC reset Vs baro" I was at my witts end. I started out reduceing them a bit, then I changed all to zero and it cured my problem. Not sure if it will have the same results for you, but its worth a try. Take and write down what values are in that table, then change them all to 0. That way, if it doesnt work, you can change them back.
Table is at 0x606. 42.xdf calls it "IAC reset Vs barometric" Marks 42-1227747-V4.3.xdf calls it "IAC baro reset"

I'm thinking seriously about a 7427 swap. Something like EBL would be nice, but since I already have the chip burning equipment, swapping in a 7427 seems to be the best/easiest/cheapest way to upgrade. I would think the more advanced code, faster speed, and higher res. tables would be reason enough to swap a 7747 for a 7427.

In the meantime, I tried zeroing out the IAC vs baro table you spoke of, and it did indeed seem to make an improvement! Thank you

If you do the 7427 swap, you wont be disappointed! If you feel comfortable swapping the pins, and are not too overwhelmed by the verry long list of parameters, go for it!
If you havent already, grab the $0D.XDF from the 7427 thread, and mabey a bin too, load them up in tuner pro and just look around. Its a lot to take in at first. When I first loaded up the xdf, I was like :yikes:, but taking what I had already learned and then just going through the xdf and reading parameter comments, I finally got brave enough to try it.
Not to say I wasnt scared though...lol. I was too chicken to jump in feet first. I went as far as finding a junk 7747, removed the harness plug from it, and sodered the wires from a 7427 directly to it, making a adapter so I could plug in my 7747 harness to the 7427. That way if it didnt work out, I could plug my 7747 back in and still drive it. Well from the first moment I toook it for a test drive with the 7427 I was hooked. NEVER hoooked the 7747 back up, it was that mutch better. I then swapped the pins to the 7427 connector and never looked back.

LOL I jumped in head first... and it still hurts, but I wouldn't use any other.

Just remember there are 1000 things in $0D compared to 100 things in $42. 90% of both usually don't need to be messed with after you get your fueling and spark in order. So don't let it overwhelm you.

Now if your motor is built well beyound stock there is more to do...

I picked up two 7427 PCMs yesterday. I have been looking around in TPRT at some 7427 bins, and yes there is quite a few more things in the 7427!!

Speaking of 7427 PCMs, I tried to carefully remove the PROMs from the MEMCALs of these PCMs..... While I did get the original PROMs removed, the "connector bed" on the MEMCAL itself where it was soldered (not sure what it's called??) that the pins of the PROM attach to got pretty mangled... I found this on thing on Moates and it looks as if it just bypasses the stock PROM, and retains the knock circuitry. http://www.moates.net/g1-memory-adapter-tpi-etc.html But can someone confirm that this is indeed what I need to get going with the 7427 PCM??? I tried to remove the PROM very carefully using this as a guide http://www.gearhead-efi.com/Fuel-Inj...r-27SF512-Chip but I ended up making quite a mess like I said. I would try to upload some pics of my MEMCAL with the stock PROM removed but I'm not sure if the pic would show enough detail?

I wish I would have found out about this G1 adapter before I removed the stock PROMs from these MEMCALs, but I guess that it's kind of a moot point since I planned on recalibrating the BIN anyways right???

BTW, if a person was to solder in a PROM or a DIP socket or whatever onto a MEMCAL, how do you solder the pins?? You can only get to it from the side and it doesn't look like there's enough room to solder anything?

And what do you do about the pins still stuck in the MEMCAL from the PROM, I snipped them off, but is there a better way?

I snip the legs off, then stuff a 27FS512 chip in, no dip, it's easier to solder the chip legs, flux the legs and pinpoint solder, must be good soldering station or iron, not cheap stuff that can't stay hot fast.

In the end the G1 is cheap easy and foolproof!

I did one memcal where I sodered in a 27sf512. I took a sodering iron tip and filed it down to a very fine tip. I then cut the chip off from the top of the legs closest to the chip as I could get, leaving as much of the legs there. I then used the fint tip iron and some very fine needle nose plires and heated and removed each pin. This left the chip "bed" or whatever its called intact and then I used the same tip and some very fine soder to attach the new chip.
All said and done, just not worth the time and trouble. I have never done another one. I bought the above adapter and never looked back. Its well worth every penny.
Actually the best deal would be to get this:
http://www.moates.net/gp1-package-gm-adapter-with-2-chips.html
That way you get a nice ZIF socket and two chips. You want that real nice zif for chip swapping. I love mine.

Well I went ahead and ordered the G1 and a ZIF to drop in it. I already have 13 of the 27SF512s so I really don't need anymore of those at this time.


Even if I messed up the MEMCAL plug where the PROM goes, it shouldn't matter since that portion is bypassed anyways by the G1 right?? The knock module and the other two little PROMS underneath it I left alone...




I'm thinking of making an adapter like you did, so I can swap back to a 7747 if I should ever want/need to for some reason... I have two extra 747 ECMs that I was thinking about desoldering the plug from to make said adapter... But you said you just ended up repinning the existing harness to work with the newer 427 PCM right?


What needs to be changed in bin when running a 427 PCM so that the PCM doesn't throw a ton of “where-the-hell-is-your-transmission” error codes?

I haven't done a lot of them but think it's as simple as taking an auto bin and checking the manual trans, then turning off error codes for tranny. There is also a 700R4 bin/patch/procedure.

Quote:

---

Originally Posted by CDeeZ

“where-the-hell-is-your-transmission” error code

---

:laugh: Had to laugh out loud on this comment. :laugh:

But yes, as mark said, simply take the bin of your choice, and check the manual transmission flags and then turn off all error codes for transmission.

Looking back, if I knew then what I knew now, I would have never even bothered with the adapter. The ammount of time spent making it was just not worth it. Just swap the pins from your harness into the plugs for the 7427. Like I said, from the first time I plugged in the 7427 and ran it, I never looked back. Now I am like 77-what?..lol

lol....

JeepsAndGuns, you're running a manual trans right?? Which bin did you use?? I'm taking your advice, I will forgo making an adapter and just swap pins...

And Mark, for your sons IH 7427 conversion.... Which bin did you use??

The reason I ask is because Mark you were kind enough to educate me several months back on the fact that IAC logic is drastically different on a AT bin versus a MT bin

So far all I've seen for manual bins using the 7427 were 4.3L V6s......

What do you all think?

We've had some deep discussion and search on that and found there never was a 5.7L manual for these PCM. So we took a 7.4L manual trans bin and modified it. I think I ended up with BHDC or BMHK which are $0E just because everyone else is running $0D, not sure what the differences are? The mask/XDF and ADX are just as well documented, not sure if all the hacks for $0D would work, but I had no intensions of doing more then TBI.

I am running BMHK, I think I might have suggested mark try it to. 454 manual trans bins were the only V8 7427 manual bins we could find. I have changed a few things on it over the time I have had it, but still has been a pretty decent one to start with.

But on that note, I did a couple weeks ago try a 350 auto bin, I copied in all my tables, and other misc changes, and selected the man trans flags and was surprised to not have any idle/iac problems. I tried a few diffrent tests. I would be driving push in the clutchand let off the gas ecpecting it to stall, it wouldnt. Would never stall coming to a stop, after downshifting, or anyhting. About the only real diffrence I did notice was when not giving it any gas while pulling out. My current bin (bmhk) will pull and go, mabey even rev a bit. The 350 bin, didnt pul as well, probably stall saver settings were just not as agressiave. I later swapped back to my old bin for a few reasons, nothing major.
So my best reccomendation, would be to simply try a couple diffrent bins and see witch one works best for you. Just remember to unhook the battery and let the pcm reset before swapping bins/code masks

Quote:

---

Originally Posted by EagleMark

We've had some deep discussion and search on that and found there never was a 5.7L manual for these PCM. So we took a 7.4L manual trans bin and modified it. I think I ended up with BHDC or BMHK which are $0E just because everyone else is running $0D, not sure what the differences are? The mask/XDF and ADX are just as well documented, not sure if all the hacks for $0D would work, but I had no intensions of doing more then TBI.

---

Yeah I didn't think there was a 5.7L/stick BIN.... Looks like I'll be trying that 454-manual bin on for size.

Quote:

---

Originally Posted by JeepsAndGuns

I am running BMHK, I think I might have suggested mark try it to. 454 manual trans bins were the only V8 7427 manual bins we could find. I have changed a few things on it over the time I have had it, but still has been a pretty decent one to start with.

But on that note, I did a couple weeks ago try a 350 auto bin, I copied in all my tables, and other misc changes, and selected the man trans flags and was surprised to not have any idle/iac problems. I tried a few diffrent tests. I would be driving push in the clutchand let off the gas ecpecting it to stall, it wouldnt. Would never stall coming to a stop, after downshifting, or anyhting. About the only real diffrence I did notice was when not giving it any gas while pulling out. My current bin (bmhk) will pull and go, mabey even rev a bit. The 350 bin, didnt pul as well, probably stall saver settings were just not as agressiave. I later swapped back to my old bin for a few reasons, nothing major.
So my best reccomendation, would be to simply try a couple diffrent bins and see witch one works best for you. Just remember to unhook the battery and let the pcm reset before swapping bins/code masks

---

Ok, I'm going to play around with several bins, but probably end up running the 454-manual bin, if nothing else I can hassle you and Mark if I have questions with the bin and mask :jfj:

I'm sure you can! :thumbsup:

Now JeepsandGuns has also just recently tried a 5.7L Auto bin with manual flag set and said it ran well with no ill effects there is still a lot of differences in IAC logic with shifting, most of which are for emmissions but side effect is slower to idle inbetween shifts making shifts easier.

Yea I figured IAC would be all kinds of screwy, but it wasn't. AE was way off, and for some reason that bin made my engine have a very light surge during accel. Went back to my old bin and it went away. Couldn't figure that one out.