88 Buick VIN 3 stalling, ECM?

[TBK]

IAT temp could be from fan blowing radiator heat on the air cleaner and
hose. I get the same effect when stopped. I should drop once you get moving.

Bulletin 88-7125-2 TCC engages in shift to reverse or drive (125C only). Bet
you have a 440.


-----Original Message-----
From: Clare Snyder <snyder at huron.net>
To: diy_efi at efi332.eng.ohio-state.edu <diy_efi at efi332.eng.ohio-state.edu>
Date: Friday, July 03, 1998 11:42 AM
Subject: Re: 88 Buick VIN 3 stalling, ECM?


>Lynn R. Erickson wrote:
>>
>> Some background:
>>
>> 88 Buick Century wagon with 3.8 SFI(hah) V6, approx. 97k miles
>>
>> My parents bought it new in 88. They decided to get rid of it about 5
>> years ago because it had always idled rough, left them stranded once
>> (crank sensor), and was intermittently prone to stalling when you let
>> off the throttle at low speed around town. Figuring that an intermittent
>> will eventually get bad enough to be continuous so that it could be
>> diagnosed, I bought the car from them for my wife. My wife likes the
>> car, and the rough idle and infrequent stall didn't bother me. _I_
>> wasn't driving it.
>>
>> However -- last week I drove it to Los Angeles and back(800+ miles each
>> way). You haven't lived until you've had a car stall in the middle lane
>> of Century Blvd. at LAX. I decided to fix the damn thing.
>>
>> Some symptoms:
>>
>> _seems_ to be heat related
>> No problems at freeway speeds
>> No ECM trouble codes
>> During the sensitive time in LA, parking lot speed bumps would cause
>> static on the AM radio and make the CE light flicker on.
>> Still idles like sh*t -- never hasn't. Not just 90 degree V6 rough,it
>> also misses.
>>
>> Diagnostics:
>>
>> All cylinders 140-150 psi compression cold. Hot? You jest! Not on my
>> skin!
>> New plugs and wires. Needed anyway. No change.
>> New PCV. Needed anyway. No Change.
>> 10" hg manifold pressure at idle. Is this normal? Reading taken from
>> transmission vacuum line.
>>
>> Got a scanner hooked up today. Following readings are at idle.
>>
>> ECM PROM ID 1254 -- The ALLDATA CD shows a stall related TSB on this,
>> but it isn't included in their (extra cost) TSB's. Sigh. ALLDATA is
>> better than Chilton's, but watch out, some of their information is
>> missing or flat out wrong (I got bit on a wiring diagram).
>>
>> Some readings:
>>                   ALDL Mode     Diag. Mode    Backup Mode*
>> RPM               1000-1100        650          675
>> Coolant Temp.     196 F            206 F        217 F
>> Intake Air Temp.  156 F (why?)     86 F         84 F
>> TPS                0.4 V           0.4 V        0.4 V
>> O2 sensor         400-600 Mv       473-549 Mv   920 Mv*
>> Spark Advance      28.6 deg        0 Deg        0 Deg
>> IAC Position       51              38           49
>> Integrator         132             129          128
>> Block Mult.        133             133          113
>> EGR Duty Cycle     0 %             89%          79%
>> EGR Switch         Off             Off          Off
>> Closed Loop        On              On           Off
>> Fuel Mix           Lean/Rich       Lean/Rich    Rich*
>> Learn              On              On           Off
>>
>> *Sets O2 sensor rich error code.
>>
>> About all I can figure out right now is to try a new ECM and get the
>> latest service release on the PROM.
>>
>> Anybody got any other ideas?
>>
>> TIA,
>>
>> Lynn
>>
>> /*********************************************************/
>> I may be stupid, but I ain't _that_ dumb.
>> lre at xmission.com   www.xmission.com/~lre
>> /*********************************************************/
>The ECU/Prom would be my first step - they have been problems. The ecu
>can not check itself, so if no codes and intermittent problems it points
>there. Likely a bad solder joint or cracked trace on a PCB.
>--
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