88 Buick VIN 3 stalling, ECM?
Clare Snyder
snyder at huron.net
Fri Jul 3 17:58:57 GMT 1998
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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