My idle hunts when in closed loop.
Idle range 600 - 800 w 30 - 40 kpa.

BLMS stay ~126 during idle.


I have a mechanical ignition, that is changing as Rpms change. I tried stifer springs, but still the ignition changes w/rpms.



When it's cold (open loop), idle is rock solid as specified (1100 - 800), but not when it goes closed loop.

I have searched and found
https://www.thirdgen.org/techbb2/sho...highlight=idle

https://www.thirdgen.org/techbb2/sho...hreadid=225984

https://www.thirdgen.org/techbb2/sho...hreadid=224960

VEs should be the same number in the idle range.
Changed

% TPS for idle is at 3.2%

IAC counts are ~20 during idle.

The throttle plates turn back to the stop screw with the spring.




** I am using a modified AXCN bin. I have taken down the VEs, upped my engine cylinder displacement size, and my AE is still pretty far off. I haven't even looked at my PEs yet.

I will look at my AE vs Delta map again...

Any suggestions?

TIA

Do you mean the timing is wandering at idle?.
If so with a mechanical distributor, then you have some mechanical problem, distributor bushings, slop in advan unit. Too soft of vac diapharm, loose timing chain, etc.

Cold, the engine is running with alot of fuel, and the timing can be off somewhat, and things seem ok.

Not to mention your running the injectors on 6v, which isn't going to help anything.

I have changed distributors... With no change.

With RPM change comes ignition change....

How can I change the injectors to 12 volts?

Thanks.

That's not a conclusive test. You can be swapping one problem for another.

Ugh, OK, so what are you saying the timing problem is?.

Change to like a 749 and redo the injector drivers, and sense resistors. There's a old thread on that. 4 TBI P+H injectors are the same load as 8 TPI P+H injectors.

OK, I found the information on the 749.

When $ permits I will be doing this swap. I am not sure how much my local j-yard wants for ECMs.

I guess I am still missing WHY I need to do this swap (7730 - 7749)...

It all appears to be working now up to 5000 rpms.

Will I also need to swap the injectors???


back to idle hunting and my timing
I rebuilt one of the distributors as far as the shaft, weights and bushings, along with a Crane adjustable kit for springs and vacuum diaghram.

I may have over looked the end-shaft bottom play (going up and down). This may need more shims.

What else should I look for in the ECM to correct this?

As I recall, idle was not a problem with these distributors running a carb.

Thanks.

I don't undersstand why you're not using the ECM to control the timing. It can do a much better job of it.

As for the 749 vs. 730, the 749 is setup to run the low impednece p&h injectors, where the 730 isn't.

Thans for the reply.

I will run the computer controlled ignition, as soon as I get one and redo the wiring.

Do I have low impedance P&H injectors?
How do I tell?

Or are all Holley TBI injectos low-impedance P&H?


BTW: I am not sure what it does or how it effects BPW, but apparently Howell changed the
INjector Puls Width Correction Vs. Battery Voltage

Hence between 20.8 - 6.4 volts Howell has the uSec. Added to + 488.29 compared to the AXCN bin.

It obviously doesn't solve the low impedance but the volts???

All TBI INjectors (that I know of) are low imp. Use an ohmmeter across the terminals of one of them. You'll have about 1.2 ohms.

So what might possibly happen with the P&H injector and a 7730???

TBI injectors are P+H, and measure 1.2 ohms

The 730 isn't designed for handling that much injector current. So to get it to run the injectors they run them in a combination of pararel and series. So as to not overload the injector drivers. But by wiring them that way, they're only working on 6 volts instead of 12.

The 749 has two out put injector drivers. With the 749 you can rewire the ecm to handle the additonal load, of the 4 TBI injectors.
there is a thread here, about how to do it, and parts to use. if your not that good at soldering then asking for assistance might get a response from one of the guys that can. I'd offer, but I just can't do that stuff any more.

The 749 was used in an application where, it fired 4 port sytle P+H injectors, but the port P+H injectors are 2.4 ohms, which is still 1/2 the load of your 4 - 1.2 ohm injectors.

Thanks for the reply, I understand what you are saying about the 7730 driving the injectors at only 6 volts, because each driver on the 7730 is going to two injectors (2 drivers x 2 injectors = 4 total injectors).

But it works.... SOOoooo What is not GOING to work using this setup? HI RPMS????

I can solder, I can read wiring diagrams. I found the infomation on the 7749, I just need to find a 7749.

The 7749 was only available in the Sunbirds??? Or what other applications is the 7749 found?

Hunting idle

I redid the ignition with the shimmed distributor bottom. I still have a hunting idle at closed loop.

I noticed my BPW changes from 1.92 - 2.23

What's up with that? Where can I check for WHY my BPW is changing at idle (600 - 800 rpms @ 38 - 43 KPA).

Thanks.

Could my O2 be bad???

I thought

ECM pulled out fuel < 128 BLMs > ECM added fuel

When in open loop (disabled Temp for closed loop) at temperature ~184 F. My AFR shows 14.81 at idle, holding idle.

When in closed loop, my BLMS go down to 122 sometimes 110 after driving around. This is pulling fuel out... right?

In open loop, driving around... my AFR shows 14.81 at idle again.

So what might be happneing? Anyone want a log who can help me?

Thanks.

Just speculating here, but you may be having an issue with some of the stuff where the ECM uses timing for idle control, and it is not happening. You are going to have a really difficult time getting this thing right because the ECM is designed to have control over the timing.

From my understanding, Idle range is where problems will come into play with an "oddball" injector setup. The time that the injectors needs to be on is so small and the lower voltage could very well be what is causing the problem.

My suggestion would be a trip to the salvage yard to pick up a 749 ECM, and a computer controlled distributor and the plugs that go with it.

Thanks for the reply.

I understand what you're saying, I have a computer-controlled distibrutor now. I need to get it wired in.

Also, I need to get a 7749. That's fine and dandy, but I am not sure which cars to find this on.

However, why would the injectors have a problem being on for short time ONLY in closed loop?

The truck runs GREAT in open-loop.

So GREAT in fact (albeit still not done tuning), I broke my 3/4 ton rear axle today on the street.

Turbo sunbird, syclone, typhoon, and 87-88 quad 4.

Maybe because the ECM isn't trying to make corrections based on the O2 sensor? I understand what you're saying here, but there are many things that just don't come into play in open loop. If the thing runs better with just open loop, set it up to run only in open loop. There are some things that you may miss out on in O/L, but if the engine likes it better, that's what you need to give it. Personally, I would try to get it to run in C/L, but sometimes, it's just not gonna get it. I've heard that there are some calibrations that run O/L at idle, all the time. That may be something that you'll be looking at.

Must be making a bunch of torque!

Thanks again for the reply and help.

It was an ARB equipped rear end... it was open at the time of explosion.


I too want it to be in C/L most, if not all the time.
I would really like to get Highway mode to work...

I was wondering how I could get it to run O/L only for idle.
Any pointers?

Now I have three reasons to go to the j-yard.
1) electric fan
2) 14FF rear end
3) 7749 ECM

Thanks for the information on the ECM series cars!

Hiway mode is a good reason to run C/L, if you drive a decent distance. Keep in mind that hiway mode is more abou tspark advance than fueling, therefore, it won't mean much (if anything) until you get the CC distributor installed.

I'm not sure if O/L at idle is possible on an $8D setup. I just looked through one of the hac's I have, and just from a glance, I don't think it will work. I'm thinking it was a 747 application that went into O/L, or maybe just a variation of O/L at idle. I'll keep my eyes peeled for it, and how they do it if I do run into it somewhere. Keep in mind, I only looked in one Hac, and I don't know all that much of the source code yet (something I've been learning for a few months in what little spare time I have!)