88 Buick VIN 3 stalling, ECM?

[TBK]

10" is low at sea level. Should be around 15 or above. Intake gaskets were
prone to leaking. Does the idle change if you remove the oil cap from the
valve cover? Disconnect the tranny vacuum modulator and plug the line to the
intake. Does the idle change? Is there oil in the vac mod line? Is there oil
in the throttle body?

TK

terryk at foothill.net

-----Original Message-----
From: Lynn R. Erickson <lre at xmission.com>
To: DIY_EFI at efi332.eng.ohio-state.edu <DIY_EFI at efi332.eng.ohio-state.edu>
Date: Thursday, July 02, 1998 11:12 PM
Subject: 88 Buick VIN 3 stalling, ECM?


>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
>/*********************************************************/
>