1990 Chevy C1500 TBI/305 stock

[zieg85]

How are the plugs and wires? Check the exhaust back pressure.

Always start with the basics. Definitely get yourself and OBDI scan tool

Thanks again Vile.  I ordered a cable, hopefully my mid level scanner can work seeing run time data.

[Captkaos]

I use WINALDL on TBI trucks (as long as it is covered.  The 1991 with 4L80E wasnt at one time.
http://www.winaldl.joby.se/

I made my own cable with some electrical probes and a Ethernet jack.
You can see it here (you have to have a 9 pin output though.  http://forum.73-87chevytrucks.com/smforum/index.php?topic=7711.msg47384#msg47384

Used it to diagnose the Suburban I had.. http://forum.73-87chevytrucks.com/smforum/index.php?topic=3984.0

What about the IAC?
Pull the distributor and check the mag pickup the burb I worked on had them rusty and bad..

[zieg85]

I use WINALDL on TBI trucks (as long as it is covered.  The 1991 with 4L80E wasnt at one time.
http://www.winaldl.joby.se/

I made my own cable with some electrical probes and a Ethernet jack.
You can see it here (you have to have a 9 pin output though.  http://forum.73-87chevytrucks.com/smforum/index.php?topic=7711.msg47384#msg47384

Used it to diagnose the Suburban I had.. http://forum.73-87chevytrucks.com/smforum/index.php?topic=3984.0

What about the IAC?
Pull the distributor and check the mag pickup the burb I worked on had them rusty and bad..

The inside of the distributor was rusty and crusty, I couldn't ever recognize the screws that held the ignition module on so I just decided to replace the entire unit and return the ignition module.  That was not the issue either.  The IAC tested within the voltage parameters in the testing procedure.  Even though the Platinum plugs looked great I changed them and that was the problem all along

[Captkaos]

...  Even though the Platinum plugs looked great I changed them and that was the problem all along

Wow that is both sad and encouraging..  All came down to plugs

[MIKE S]

Did you change the gap on the platinum plugs? You can't run a gapper between the electrodes on a platinum or iridium plug. Even the slightest amount of drag will disturb the platinum and could have caused your problem.

[VileZambonie]

Even though the Platinum plugs looked great

Please don't say you used Bosch Platinum's 

[zieg85]

Even though the Platinum plugs looked great

Please don't say you used Bosch Platinum's 

no but that was what was in it.  Put some AC non platinum

[VileZambonie]

no but that was what was in it.

They are absolute garbage

[zieg85]

no but that was what was in it.

They are absolute garbage

Good to know...  I got about 150 miles down the road and my service engine light came on and went off.  Truck started bogging real bad and barely made it safely to a parking lot where my son came and got me with a uhaul dolly.  Anyway my brother in law came with an OBD1 scanner.  All tests pointed to the MAP sensor.  Changed it and that wasn't it.  I really don't know where to turn.  He is going to do some checking tomorrow and see if he can come up with something else.

[Asphalt Dr]

Have you checked the fuel filter?


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[zieg85]

Have you checked the fuel filter?


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New fuel filter less than 250 miles ago

[bd]

Before drifting too far afield, verify the fuel pressure.

[zieg85]

Before drifting too far afield, verify the fuel pressure.

Some run time data, weird voltage reading and re-ac curing code 42 and 44 with the known history of the truck are pointing to wiring based on a very similar situation reported on a mechanics resource my brother in law sent me to try.

[Captkaos]

This is the Diagnostic for 42:
http://forum.73-87chevytrucks.com/smforum/index.php?topic=36657.msg308237#msg308237

44 means lean so I too say check fuel pressure.  What does the TBI regulator look like.  I had one with a broken spring...

[VileZambonie]

Before drifting too far afield, verify the fuel pressure.

Put the parts cannon away. Check the basics, fuel pressure, proper timing set, and preliminary checks before you buy parts.