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

[Jim's Inbox]

Try that me cal in another ecu to see if the problem follows it.

Jim

On Mar 17, 2013, at 11:18 AM, "David Allen" <davida1 at hiwaay.net> wrote:

> 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
> To: terry ; 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
> 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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