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View Full Version : Consistent/Repeatable Timing fallback to 10deg looking for suggestions



Peterdroy66
08-11-2009, 02:05 PM
92 5Spd
symptom: intermittent poor idle, failing timing advance

When: CAN BE CAUSED by idling too low - ie letting clutch out too slow, but will also cause randomly sitting at idle, or coasting to a stop.
CAN be cleared 80% of the time by taking RPMS up over 1600 rpm.

The above observations are very consistent and repeatable.

I can see on diagnostics interface (EASE COMPUTER), the timing is clearly loosing its 'commanded' advance.

For example at idle it is normallly 20-21degrees fluctuating normally, when the condition is brought on, it clearly drops to a rock solid 10degrees.

Last night, against my gut but running out of tricks to try, I replaced the DIS with a new FORD part.

I cannot bring this on by any wire wiggling under the hood.

Battery voltage, and 5V logic voltage are remaining stable under all conditions.

I tried some additional ground wires at various places to the battery/body with no improvement.

I would consider fuel pressure/pump, however watching the ignition timing really points to an ignition issue.

Again, it is too regular to be an intermittent or bad wire somewhere.

My main thought is that SOMETHING is CAUSING the EEC to stop sending timing information, but I do not know what or why?

Looking of experienced suggestions/input.

Pete in Toronto

KMT
08-11-2009, 02:38 PM
In rare cases, external issues can create knocking that the sensor picks up, resulting in the computer pulling timing.

Those issues can include:
- failed motor mounts
- cracked flex plate
- broken auto trans converter bolts
- rattling manual trans (there was a recall for this)
- very low octane fuel (not likely)

You get the idea. The result is spooks such as you may be seeing...just a head's up as you seem to be out of ideas otherwise. Good luck w/your issue(s) in any case.

QuickMustang
08-11-2009, 02:50 PM
check to make sure your TPS is always going back to a consistent .96 volts at idle. I had a similar problem on mine and it was caused by the TPS voltage not dropping back to the same value every time because it's set point was set below the repeatable range of the sensor (about .85 volts). So when I let off the gas, sometimes the computer wouldn't read that as closed throttle and it would then go off of a base timing table rather than the standard idle conditions where it was capable of adjusting the spark to hold the ideal idle rpm.

fturner
08-11-2009, 02:52 PM
Knock sensor isn't active until the EEC sees 55% load or higher. His idle load is around 15%.

Fraser

Peterdroy66
08-12-2009, 09:35 AM
Changed CAM sensor because it is easy and I have another SC close at hand.
NO IMPROVEMENT.

Played with RPMs and throttle position driving it this morning, and the problem seams to be VERY dependent on RPMs, not TPS.
Can get it to happen when bogging the engine on a clutch out start, then at ANY throttle position as it passes 1600rpm, can clearly feel the ignition recover as the car surges.

PEte

S_Mazza
08-12-2009, 10:26 AM
Try cleaning the MAF.

frdlvr30
08-12-2009, 11:43 AM
I'd have a look at the spout connector and wiring as well....

XR7 Dave
08-12-2009, 12:49 PM
If it's that consistent and repeatable then it's most likely something in the tune. I realize that you guys have gone over this a million times but most likely you'll have to start over with a stock tune and start making changes until you pinpoint the one that is causing the issue.

fturner
08-12-2009, 01:11 PM
My datalogs show the car occasionally starting up with 0 degrees of timing and requires a rev to bring it to what its suppose to be. When the stall occurs it goes to 0 degree's of timing, not 10 as Peter's Ease system indicates. This behaviour was not consistent as it could happen anytime as the car could be driven 5 times in a row with no issues. Its not that consistent as the occurence is random.

The tune has been restarted 3 times from scratch with 2 different stock bin's.

If it is the tune, then its something way beyond my level of comprehension as to what is causing this and will require a more experienced tuner to solve.

Fraser

ps. The car did the same thing even with just the injector size plugged in at the start of a fresh tune (its still the stock MAF).

XR7 Dave
08-12-2009, 01:59 PM
Anyone have a stock 91-93 SC they would be willing to swap EEC's with? That would be one way to verify that Peter's EEC is or is not capable of totally stock operation....

fturner
08-12-2009, 02:25 PM
Is there a way to monitor the spout signal directly?

This is direct from the strategy document...

quote-----
SPOUT is initialized low on EEC-IV processor power-up and will remain low
through CRANK and UNDERSPEED engine modes causing spark to be delivered at 10
degrees BTDC. Upon transition into RUN mode, the EEC-IV processor will
schedule a low-to-high transition of the SPOUT line to occur at 20 degrees
ATDC of each cylinder followed by a high-to-low transition SAPW microseconds
later. If the SPOUT line remains in either a high or low state for more than
one PIP period or if the pulsewidth of the signal is outside the clip limits,
the HESC module will assume an EEC-IV processor failure and revert to spark
placement at 10 degrees BTDC.
-----unquote

Fraser

XR7 Dave
08-12-2009, 02:44 PM
If the SPOUT line remains in either a high or low state for more than one PIP period or if the pulsewidth of the signal is outside the clip limits, the HESC module will assume an EEC-IV processor failure and revert to spark placement at 10 degrees BTDC.


This is probably key and in line with what I was already expecting. If PIP is beyond a clip value, it will revert to base timing. At low rpm PIP is longer, and in this case apparently about 800 rpm shortens whatever PIP is present to where the EEC no longer recognizes a valid signal, and 1600 rpm generates a short enough PIP for the EEC to consider it valid again. Two possibilities seem apparent. 1) The clip value is set too low (too high rpm) somehow, or 2) at idle the PIP signal is "dirty" making it difficult for the EEC to validate it.

Since he has already replaced the cam sensor, it remains that possibly the CPS signal is weak or that the ground shield on the sensor harnesses has been compromised. I tend towards a compromised shield ground.....

Peterdroy66
08-12-2009, 02:57 PM
This sounds very very close to something like what we are looking for.
I should be able to put a portable scope on the spout line, and maybe channel 2 on the PIP.

PEter

S_Mazza
08-12-2009, 08:13 PM
Is there a way to monitor the spout signal directly?

This is direct from the strategy document...

quote-----
SPOUT is initialized low on EEC-IV processor power-up and will remain low
through CRANK and UNDERSPEED engine modes causing spark to be delivered at 10
degrees BTDC. Upon transition into RUN mode, the EEC-IV processor will
schedule a low-to-high transition of the SPOUT line to occur at 20 degrees
ATDC of each cylinder followed by a high-to-low transition SAPW microseconds
later. If the SPOUT line remains in either a high or low state for more than
one PIP period or if the pulsewidth of the signal is outside the clip limits,
the HESC module will assume an EEC-IV processor failure and revert to spark
placement at 10 degrees BTDC.
-----unquote

Fraser

Smartypants. :p Nice find.

Peterdroy66
09-14-2009, 06:21 PM
I have finally been able to put a scope on PIP and SPOUT.
Basically both look fine, rock solid square wave, varies with RPM.
When the 'failure mode' surfaces, SPOUT IS STILL PRESENT and unchanged.
I may try again later tonight and see if when the 'failure mode' is invoked, if IDM signal changes, this might indicate a coil issue, easy enough also to swap out coils with another car and see what happens.
Pete

fturner
09-14-2009, 06:25 PM
Hey Peter, where are you testing this.. at the DIS or at the EEC?

If it is getting a good signal at the EEC, then I'd say its time to find another EEC and plug it in.

Fraser

Peterdroy66
09-14-2009, 07:39 PM
Fraser
I had the scope right on the wires at the DIS.
I may swap coil packs because this is easy, and also because I do not know what I should expect to see on the IDM line if the problem is present.
Peter

Peterdroy66
09-14-2009, 07:52 PM
Just ran a self test, because the FORD FUEL INJECTION and electronic engine control book shows several codes which should be saved in continuous memory if there is for example loss of SPOUT/grounded spout, 'erratic' IDM signal, or loss of IDM etc etc
There are no stored codes like any of these in the continuous memory....

Pete

fturner
09-14-2009, 08:01 PM
Look around for someone that has the M2Y EEC and swap it out.

Fraser

Peterdroy66
10-13-2009, 11:37 PM
Well, now having DD replace the CAM with something more suitable, the car makes low end torque like it never did with the lousy cam I had in it.
I have not looked at it with the computer, however the symptoms are completely gone. Even if steering is loaded, or something turns on at idle, the engine no longer stumbles misses a beat or anything, it just simply idles there unbothered around 750/800 rpm.

I know this isn't a complete definitive - root cause solution, but after xxxxx around with the lousy cam for the last two summers, it finally now drives properly with low speed torque like a supercoupe again!

Regards
Pete

Toms-SC
10-14-2009, 02:01 PM
Peter,what were the old and current cam specs?