TPI HELP

[John Hess]

You might check the "open loop" idle setting.:

With the ignition "ON" and the engine not running, short Terminal "A" 
to "B" in the diagnostic connector (ALDL).  This will close the IAC 
(Idle Air Control) motor and block the idle air passage (hold this way 
for about 30 seconds to make sure it fully closes).  While the IAC is 
closed, remove the 4 pin connector from it, then remove the shorting 
clip and turn the ignition off (CAUTION, do not start the engine with 
the pins on the ALDL shorted).  Start the engine and adjust the 
throttle stop screw to give a 450 to 500 RPM idle (with automatic 
transmission cars in drive).  Turn off the ignition and reconnect the 
IAC connector.  The neutral idle speed should be the same as before 
(700-800 rpm after about 30 seconds).  Drive the vehicle to be sure 
the stalling problem is corrected.  If all is OK, reset your TPS 
(Throttle Position Sensor) voltage to .5 to .6 volts (.55 is optimum) 
at idle.

Also note the posts regarding carbon buildup in the throttle body and 
plenum, as these can have adverse effects at idle and throughout the 
range, as well.


----------
From:  George M. Dailey[SMTP:gmd at tecinfo.com]
Sent:  Thursday, February 27, 1997 7:35 PM
To:  diy_efi at coulomb.eng.ohio-state.edu
Cc:  jmosley at tecinfo.com
Subject:  Re: TPI HELP

I think one or more sensors may be throwing in a wrong value that is 
within
what the ECM expects to see. Disconnect the MAF and run the truck in 
the
resulting Limp home mode. If it doesn't stumble, check for intermit 
problems
in the MAF and or related circuits. Connect a volt meter to the TPS 
sensor
and make sure that the voltage doesn't change when the throttle isn't
moving. If this doesn't find the problem, you can add this to the list 
of
what's right.

Good luck and keep the guns and dangerous tool out of your reach.
Troubleshooting can push a person to the edge of insanity :)
GMD
At 07:51 PM 2/26/97 -0800, you wrote:
>Hi all
>
>        Wanted to get some advise\help with a problem that just 
started
>happening. My pickup started to die on me, usually just after a 
corner or
>coming to a stop, just leaving a stop. Will restart with no 
difficulty. The
>pickup has a TPI unit out of an 86 Camaro with a 89 eprom. Has been 
driven
>for 2.5 years without a problem.
>        Have checked fuel pressure 42 psi when problem occurs. 
Battery
>voltage at 14.6 running. Monitored voltage for injector feed(both 
banks),
>ecm feed-all are stable. Ohmed out injectors hot- 17 ohms :(, egr sol 
 38
>ohms, purge sol 24 ohms . Didn't ohm out idle motor or TPS. Have 
flexed and
>wiggle most all connectors\parts of wire harness. NO trouble codes. 
Do not
>have a scan tool or access to one. Beginning to suspect problem 
inside ecm.
>Local wrecking yard wants 75$, rebuilt one from NAPA 130$.  Didn't 
want to
>spend that kind of money on a blind test, unless I have to.
>
>
>Thanks Vance
>
>
>