[Gmecm] Crazy 7730 problem - random numbers for TPS & ECMverywarm...

[Beau Blankenship]

I had one of the adapters from Moates go bad (it got some moisture on it)
but re-flowed solder joints and it worked fine after that. I also had
MULTIPLE 7447 Eproms go bad. Not sure what chips you are using, but, it
happens.

 

Beau 

 

 

From: gmecm-bounces at diy-efi.org [mailto:gmecm-bounces at diy-efi.org] On Behalf
Of David Allen
Sent: Sunday, March 17, 2013 11:18 AM
To: gmecm at diy-efi.org
Subject: Re: [Gmecm] Crazy 7730 problem - random numbers for TPS &
ECMverywarm...

 

And the answer is......

 

...a bad MEMCAL!

 

I don't know how it caused this, but changing to another MEMCAL (with the
same program in it) cured the problem.

 

I erased and re-programmed that MEMCAL and again it did the same thing no
matter what program I install in it. 

 

That one goes in the trash.

 

Later,

David

----- Original Message ----- 

From: David Allen <mailto:davida1 at hiwaay.net>  

To: terry <mailto:tl34ru at yahoo.com>  ; gmecm at diy-efi.org 

Sent: Sunday, March 17, 2013 8:46 AM

Subject: Re: [Gmecm] Crazy 7730 problem - random numbers for TPS &
ECMverywarm...

 

It's a 1987 car, with a newer model ECM, possibly an early 90's ECM. 

 

I'm going to check some things this morning and will see what the grounds
look like.

 

Thanks!

David

----- Original Message ----- 

From: terry <mailto:tl34ru at yahoo.com>  

To: gmecm at diy-efi.org 

Sent: Saturday, March 16, 2013 10:51 PM

Subject: Re: [Gmecm] Crazy 7730 problem - random numbers for TPS & ECM
verywarm...

 

David,

What year Buick are you working on? I have had issues with ground circuits
on that ecm where the terminals become loose 

cause skewed the data.

Terry

 

From: David Allen <davida1 at hiwaay.net>
To: GM-ECM <gmecm at diy-efi.org> 
Sent: Saturday, March 16, 2013 11:35 PM
Subject: [Gmecm] Crazy 7730 problem - random numbers for TPS & ECM very
warm...


Hello guys, I've got a stumper of a problem.

Just finished re-pinning a MAF ECM (old 3.8 Buick, has the 2 connectors) for

a 7730.

I powered it up to see the data on the computer, and I get some strange 
things.
The fuel pump prime function and Check Engine light function as normal.

When first powered up, the TPS shows a seemingly normal voltage. The TPS 
reading will move with the pedal position. Then, gradually, it starts to 
read a bogus higher and higher voltage, eventually stopping about 3V, with 
no change when the pedal is moved.  Verifying with a meter, the TPS voltage 
is stable at 0.5V and does operate normally with the throttle.

The second thing is, the MAP reading is fixed at approx. 60 kPa. The MAP 
sensor voltage is correct (measured with meter) and does fluctuate with 
vacuum.

Then, the ECM gets warm, after 3 or 4 minutes. This is without starting the 
engine or activating anything.

I have disconnected everything from the ECM other than the "A/B" connector, 
and powered it up. The scan data does the same thing, TPS starts at low, and

after a few minutes it climbs.

The TPS issue will return to normal (for a few moments) if I power off the 
ECM and power on again. The MAP never reads other than approx 60 at any 
time.

The sensor +5V reference and sensor ground are correct and never fluctuate 
even as the readings drift.

I thought the ECM was damaged, so I tried another one. It did the same 
thing. I know both these ECM's have worked correctly before.

I'm running Code59 V.23 exactly the same as another identical engine which 
runs fine.

I've used the same diagram for 2 other conversions, and they both worked 
fine. I am at a loss.

Thanks for any insight!
Sincerely,
David 

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