After sorting out various problems with the help of this fine forum (thanks to everyone helping me out) I could read why my TCC is locking in second gear and why it is very reluctant to release. It is the ECM calling for it and not expected cable and connecotr problems.
In order to find the problem, I really need to know under which circumstances the ECM does call for a TCC lock
1984 CFI, ECM 1226026
Please chime in speciallists (Doctor? you know this)

 

No, I think I said yesterday that's a VERY old ECM - and I've never run across a program listing of its content.

I did give you a reference for similar TBI computers, which includes this entire write-up on torque converter clutch
(TCC) operation:
http://www.thirdgen.org/techboard/di...ad-vs-mph.html

Reading through that, you discovered the ECM calls for certain conditions (Vehicle Speed, RPM, TPS) for the TCC
lock/unlock function. Those conditions can be changed in the ECM program ONLY, and are specific to individual
car models.

As previously mentioned, there is one guy in Sweden who might have program info for an '84 Vette. You could also
try a Google search for "Crossfire" or "Xfire" manifolds - seems to me there was a web site for owners of such.


I don't know for a fact if anybody ever hacked the 1226026 program or not. What few details of the computer
I found were on this site: http://www.cruzers.com/~ludis/

There is also one old-time tuner I know whose files MIGHT go back that far (he works for money though) -
http://westers_garage.eidnet.org - you could check with him, he's in western Canada.


Best of luck with your search.

 

This is really a good write-up It gives me insight info I really can use. Thanks a lot. I will try to check with this why it locks that fast. I cant immagine that it should do that, neither can I immagine that a fusable ling Prom will change its info. I did take the prom out and mated it again to ensure that the contacs were clean. There may be something not adjusted well or so.
I really appreciate your help Doctor J,
Keep you posted.

 

You know, I thought about it more. Seems like you have two choices, neither very easy:

1. Keep looking for ECM info for an OBSOLETE computer.

[You might also ask for program information on the TGO board or the DIY_EFI board:
http://diy-efi.org/gmecm/
http://www.thirdgen.org/techboard/diy-prom/ ]

Even if you succeed, you still have a primitive control system, with no spare parts easily available. OR


2. Upgrade to a more modern ECM. Some people report good results with the 8625-type ECMs from
early 90's GM pick-up trucks. There is a partial hack of that software around, done by Ken C of HPTuners
some years ago IIRC.

The only real problem I see is your need to drive two IAC motors in parallel. I don't know for a fact if
the driver on the ECM board can handle two IAC motors, but with your background in EE, lashing up an
outboard power driver shouldn't be a big issue.

See the discussion of ECM conversion going on here:
http://www.thirdgen.org/techboard/di...-its-time.html

That would give you a MODERN computer with greatly improved control features and diagnostic
capability.


HEY! Just noticed in that conversion thread that 'ben73' (in Australia) had a 6026 ECM. That might
be another resource in your search for program info.

PS You still didn't answer my question about that bar near Marbella. It was outside the big marina, on
the road between Marbella and Gibraltar.

 

I will check on these guys. Thanks a lot for the links. The idea of changing ECM is appealing, especially because I like to mount 1.6 RR´s in future, headers and port the hell out of my intake manifold.
I did some more testing, mounted a lamp in parrallel to the TCC coil in order to watch when is is commanded ON. It does that at approx 15 Miles an hour, seems very low to me. The HELMS calls for more than 40 in fourth only. But I have third and fouth (and now second as well ) It stays on until I slow down to 15 again. Could not get it off by pushing the throttle, but tested very briefly, it is late here. It really looks like that the only factor for TCC engagement is speed. The TCC is off when in open loop though. So everything looks OK except the very low speed. Tomorrow I will do more tests and check if the speed is scanned correctly. The TPS was calibrated OK, the scan did read the same value and the value responded at throttle.
So I indeed seem to have an ECM problem, but perhaps due to an other reason.
I don not know that bar, I don´t come in that region too often. It is approx 45 minutes drive. (20 with the Corvette ) And there are sufficient good bars close by

 

ttt

 

Hey guys, found someone with exactly the same problem at an other forum. He said it was an ECM fault. So this IS possible. I considered it so strange for a software problem, that I concentrated at wrong ECM inputs.
He did mount switches and a relay to get it at WOT and in 4th only.
I did add a TCC disable switch for the time being in order improve drivability in heavy traffic. But now I will try to get me an other ECM (1226026) to test.
ttt me up again Pete? How is the vacation going, must be quite an experience after so much time!!
Take care

 

Do you have 2 speed sensors, one for the dash display, and the other for the ECM? Could the second be sending the wrong speed info and locking you in second gear. I'm new at this, so forgive my ignorance if this is not correct for your year.

 

There was a TSB for the 84's where they would reprogram or put in a new chip to delay the TCC lockup to 44 MPH. When I bought mine it obviously had not been done. Jerked badly in and out so much that I thought it was running poorly. I bought a chip off eBay for 25 bucks (Hyper something or another) that took care of the problem. It was also supposed to increase the HP (yeah right). List price was like $144 but I was willing to spend 25 bucks to delay TCC until 44 MPH. It made it a hole new car - much more fun to drive. I too am considering an upgrade to the ECM and will most likely go with the 7747.

 

No,there is one speed sensor that is connected to the dash cluster. That processes the speed and displays it. It also transmits the information to the ECM by a serial link. I checked the speed info at the ECM by scanning. It is correct and the same as the dash displays.
Thanks for thinking with me.

 

Hey MADinAK, that good info. Thanks. MY manual tells me that the ECM should lock at 44 miles/hr. But I have quite an early model 1984 Vette, it may have the TCC early lock.
Because there is obviously almost no one that does programming for the CFI engine 6026 ECM, upgrading to a 7747 may be the best bet. But I am a digital moron, so it scares me a bit. With analog electronics I have no problems, but if there are program problems, I am lost. I can´t program myself to learn programming either.

 

Nicolaas-

1. I was looking for something in the FAQ thread the other day and noticed a reference to 6026 ECMs.
The author expected to finish a hack of the software 'soon' - but the entry is dated in 2001 .

As it appears, the earliest Corvette ECMs ('82-85?) are not well-supported by software development. Nobody
really spends much time working on hardware that old.



2. 'Programming' may not be as difficult as you think. Most people just use a 'PROGRAM EDITOR' to adjust
the ECM operating conditions, without knowing a thing about how the computer works... So long
as your engine is not too far out, and the ECM is supported by after-market developers, standard GM
software can be adapted to run it with few problems - using either a Commercial or 'Free' editing package.


3. There a little introduction to the process here: http://forums.corvetteforum.com/show....php?t=1158025


4. Look on the TunerCat site http://tunercat.com/ and open the information files for the 16168625,
16196395 or 16197427 ECMs (GM trucks used a 5.7L TBI engine). If you look under the data definitions
("I" symbol) for the $E6 or $0D programs, there are pdf documents showing which ECM parameters can
be adjusted with the TunerCat Editing package. As long as you stay within those adjustments,
no further work is needed to the ECM code.


5. Getting into the ECM code itself is only needed when the engines and cams get too far away from stock,
or when you want to understand(or change) exactly how the ECM program acts. Very few people really go there -
except on the TGO board. And when you jump to the later software of the C5/C6 Corvettes, the numbers
dwindle down to just a handful of people.


6. If you would rather just force inputs to an ECM and observe the outputs (or evaluate software changes
away from the car) a Test Bench is easy to build and use with a spare ECM and some connectors:
http://www.thirdgen.org/techboard/at...g?d=1147456164


Hope that helps.

 

Thats GREAT info Doctor, really appreciate it. It makes it very tempting to change things. I like to try the TCC locking first and like to find out where the ECM does command locking. If that verifies the practical values, I must be able to change that with this info.
It may take a while though, I just accepted a new development of a plasma sterelisation installation, really an other invention. That will keep me out of the bar for a while and the programming has to wait a while.
But I stored your links in my favorite, so I can find them back
I will keep you posted if I am that far.
Thanks a lot again
Nico

 

Don't know if this will help but check this
http://www.tciauto.com/gm/gm_4L60E.htm

They have a lock up kit that might slove your problem.Or you could always go to a stick and dump ther auto but I know what you just went through to get it so I guess it is not an option.

I think you could unplug the ecm and install the kit to get what you want.

 

I do have a hack of the 6026 code, but it is not very well documented at all. I also have a .ecu/xdf with limited tuning parameters available..
It does have the TCC lock/unlock speeds though..

GM did release a revision of the '84 chip at some time that did raise the TCC points from somewhere around 27mph to 44mph. I have copies of both .bins, and maybe an ADS one also that includes the TCC mods and some extra timing during PE...

If you send me an email I can hook you up with the files, but I can no longer burn a 2532 chip as I have none left that work....