Blue70

As most of you have probably read, I am having problems with my 82 Vette. It is running, but the advance is not working. Can I put an EST module in place of the standard module in a vacuum advance HEI distributor?
My thinking is the vacuum advance would take care of it self and the EST will still give the CPU the RPM signal and the car will run OK again.

Any thoughts??

Blue70

TT any thoughts on this one?? I am at the end of my rope, I need my car

Twin_Turbo

No, because the EST is what replaces the vac. advance. The EST (and ECM) control the advance. Your distributor is the same as those used in C4s up to 91. The vac. adbance will not work with the ECM, you will get serious problems with timing control and knock control. I think what you are saying is put an EST module in the vac hei so the ECM sees it but in fact it's not functional with the vac. module controlling the real advance to the plugs right?

The EST system is real sturdy, if you have an advance problem it's either the EST, the ECM or the distributor/wiring. ECM has been replaced and so has the EST right? You mgiht want to check your wiring. Is the HEI bypass lead connected? It's a tan wire w/ brown connector that comes off the distributor. The conenctor to unplug it (to set base timing) is near the brake booster. If that thing is disconnected it will never advance at all.

Blue70

Yes, 3 new ESTs and 1 new ECM. Brown wire was unhooked to set timing at 6deg, but it is hooked back up now.
We are not getting the 4.6 volts for the EST bypass signal, we tried to fake it out by giving the wire 5volts and there was no change in timing....what are we missing??

Twin_Turbo

The diagram I posted lists voltages for a warm engine, running in closed loop, idling and the test terminal not grounded (ALD test/ground jumper)

Try that, jumper the ALDL and see if the timing changes.

The 4.6 V is not there with the engine in open loop or not running & key on. Then there's 0 volts there. If it's not in closed loop applying 5V won't do a thing.

The hei spark timing wire is white if I'm not mistaking, there's 4 wires from the EST side of the module, they are distr. reference pulse input, distr. reference pulse ground (those 2 are shielded), HEI sparkl timing (white) and HEI bypass (tan)

Blue70

what pins should I have him jump where, and what's it doing?
What would keep it from running in closed loop, the car's fully warmed up?

Blue70

I think what you are saying is put an EST module in the vac hei so the ECM sees it but in fact it's not functional with the vac. module controlling the real advance to the plugs right?

Ya, that's what I was thinking. Let the ECM think it's still there, and get the RPM signals from it or whatever, but leave the tan wire in the 4 wires going to the distributor unhooked and let the vacuum/mechanical advance take care of the timing advance, and let the computer work the fuel delivery....as a last choice, I need my car back by the weekend, my wife is going on vaca next week with hers

Blue70

Do you think that would work as a last resort?
I would rather have it work the way it should

Twin_Turbo

The ALDL connector is under the ashtray. The 1st 2 pins are ground & test (diagnostics), if you jumper them the system goes into field diagnostic mode and will dile at about 1000rpm (fixed) with fixed timing. Also, the CTS signal influences ignition timing, try swapping the CTS for a 640Ohm resistor. Open loop will be engaged but total timing should change from what it was before (don't run in this mode, or the aldl mode, the TCC won't work and you will easily overheat/burn the tranny)

Here's the resistor values for the jumper to forcefully set ECM modes:

0 Ohm -> jumpered short = Field Service Mode
3,9K Ohm (3900 Ohm) = Back up mode, this is the limp home mode.
10K Ohm (10.000 Ohm) = special mode, it's a forced closed loop mode,idle fixed at 1000 rpm (fixed IAC pos #)
open (no jumper) = normal mode, what it is in when you normally drive the car.

When you jumper with a 0 Ohm resistance (wire) you will see the check engine light flash. With the engine off it flashes trouble codes, starting with 12 (this is sort of a check code to see if the diagnostics work, in reality it's a no rpm signal code and it is always set when key is on and engine off, system = active but no rpm. It's because of the design of the system that it's always set) Each code will be flashed 3 times and when 12 appears again it's displayed all the codes.

A code is a series of flashes and pauses, 42 for instance will be:
flas..flash..flash..flash ____ flash.. flash

where .. = short pause, ____ = longer pause. An even longer pause is given between codes.





Here's a list of codes:

12
No tach signal to ECM

13
Oxygen sensor

14
Coolant sensor circuit voltage low

15
Coolant sensor circuit voltage high

16
NOT USED

17
NOT USED

18
NOT USED

19
NOT USED

20
NOT USED

21
Throttle position sensor voltage high

22
Throttle position sensor voltage low

23
Manifold Air temperature high NOT USED

24
Vehicle speed sensor

25
Manifold Air temperature low NOT USED

26
NOT USED

27
NOT USED

28
NOT USED

29
NOT USED

30
NOT USED

31
NOT USED

32
EGR system malfunction

33
MAF/MAP sensor too high

34
MAF/MAP sensor too low

35
Idle speed control error

36
MAF burnoff problem (BOSH) NOT USED

37
NOT USED

38
NOT USED

39
NOT USED

40
NOT USED

41
Interruption signal tach to ECM

42
EST (Electronic Spark Timing) problem

43
ESC (Electronic Spark Control) problem/Knock sensor

44
Lean exhaust condition

45
Rich exhaust condition

46
NOT USED

47
NOT USED

48
NOT USED

49
NOT USED

50
NOT USED

51
Defective/improper installed Prom

52
CALPAK (MEMCAL) missing

53
High battery voltage

54
Low fuelpump voltage

55
ECM defective

56
NOT USED

57
NOT USED

58
NOT USED

59
NOT USED

60
NOT USED



ECM modes:
The ECM controls the injection system, it fuctions in either one of these different modes:

1.Shutdown Mode..
When the ignition is off for 2 or more seconds. Only the RAM (trouble codes) and the BLM remain powered.

2.Startup Mode.
When engine is cranked. Timing is locked at initial starup and air/fuel ratio is enriched. This mode is on for about two seconds after starting to ensure the engine will continue to run.

3. CLOSED LOOP.
When the engine is warmed up, the oxygen sensor is heated up properly and a certain amount of time has passed. The ECM will read all the data coming from the different sensors and will regulate the engine with this information.

In closed loop mode the ECM has 2 differend modes;

a. Enleanment Mode<.br> When the throttle is closed.

b. Enrichment Mode.

At wide open throttle.
High engine load.
High engine RPM.
Overheating engine. (the cold fuel is a great contributor to engine cooling)

The ECM is normally in enleanment mode, it constantly lowers fuel addition. When the oxygen sensor detects a lean condition enrichment mdode is entered untill the oxygen sensor doesn't sense a lean condition anymore. Than enleanment is entered again. This (theoretic) gaurantees an "ideal" air/fuel ratio.

4. OPEN LOOP.
When the engine hasn't warmed up, the oxygen sensor isn't warmed up properly or a certain amount of time hasn't passed. The ECM is controlling engine variables through the BLM function of the RAM.

5. Fuel cutoff Mode.
When the throttle is closed and the MAP sensor notices a negative load (deceleration) untill about 1500 RPM..

6. Clear flood Mode.
When throttle is depressed more than 80% while cranking. Injectors are turned off or air/fuel ratio is lowered to 20:1.

7. Limp Home Mode.
When there is major trouble with any of the critical sensors/actuators.


Here's the ESC by the way:

61
NOT USED

62
NOT USED

63
MAP too high (2.8L genII only) NOT USED

Blue70

Thanks again TT
The information was passed on to the mechanic, he is taking it personal now, he is determined to figure out what is giving him the problems with this car.
I think you need a sunny North Carolina vacation...I have a free room if you fix my car

Twin_Turbo

You couldn't afford the beer needed to fuel me