Hello all

I have had this problem for a while and this seems to be the best source of TBI info I can find.

Hope y'all can help.

I have a 1987 350 with TBI in my 81 truck. The swap was done to a high standard.

Here's the problem I'm having that no one including me can seem to put their finger on.

The engine will shut off regularly by itself as if you turn it off. No stumble or sputtering. It just shuts off.

It also sputters and misfires underload but this is intermittent

It can be kept alive by anticipating the shutoff, feathering the throttle will keep it alive.

When it does shut itself off it starts right back up. No need to touch the gas, 4 to 6 cranks and it fires right up.

I've checked EGR, it moves freely. I've replaced the CTS, checked the voltage at the TPS which is fine. Checked all vacuum lines etc.

I'm a little stumped any suggestions would be more than welcome!

 

Well if it was an 1987 truck it could be a million things but since it's a converstion 2 million!

Any codes set?

What is your fuel pressure at idle?

What is your voltage at idle? Old trucks do not have charging systems that EFI cars/trucks do.

Good grounds from ECM are always an issue with conversions. There's also electrical interference that can be caused by where you ran your harness or if your coil wire is near any wiring or sensors.

One part of these systems is known to cause intermittent glitches and it is the EST module mounted in the distributor, if your parts store can check it ask them to do it three times. If it fails any one it is bad.

There's also a GM Trouble shooting manual in pdf you can download to check any circut of these systems at bottom of page:
http://www.gearhead-efi.com/Fuel-Inj...-CEL-SES-Light

 

I'll check the fuel pressure and grounds, though again, it starts right up. bad wiring should have the problem persist if not just for a little bit.

the conversion was not done by me but I have done several and can say this has been done very nicely.

I will pull the EST and check it * Electronic Spark Timing?*

thanks for the link but other ideas are welcome

 

Done nicely is good! Does not mean everything is correct. Heck brand new parts come bad sometimes?

Wiring can run perfect, then die, then run intermittent, could be a loose connection anywhere?

Since it's a conversion you have to look at any and all connections. A bad ground on the fuel pump could cause what you explaining as well. HTH!

 

All very solid and good points but believe me when I say: I've been through quite a lot on this truck so far.

what's HTH?

 

Hope That Helps!

 

Sounds like spark is failing, Id replace the ignition control module! Not very expensive, and pretty easy to install! Right under the cap, check the cap while your doing the install!

Does the battery indicator drop to 0 when this happens or does it stay normal?
If it drops to 0 it's possibly a bad ground.