TBI timing help…

[bucket]

The injectors should not continue to spray after stalling. I might recommend a cheap oscilloscope so you can see the injector trigger and start diagnosing that.

It's also possible they are just leaking and bleeding off fuel pressure.

 

[Ricko1966]

I'm assuming you bought this truck used at some point in time and have never timed it yourself until now,so you dont know how P.O.timed it andvwhy. I would not assume the coil,distributor and ecm all went bad at the same time. That being said it is now running so obviously whatever went bad to keep it from running has been replaced. First make quadruple sure,you didn't create your own idle proplem while you were replacing parts. Knocked off a vacuum line,unplugged a wire etc. Now put away the timing light and start timing it by ear. It ran before,there's a sweet spot and you need to find it again. Then if you are worried about it you can do some reverse engineering to figure out why it won't run at factory setting.

 

[Vbb199]

Nobodies suggested it, so i'll be the first.

Try swapping the ESC module for another one.

 

[Vbb199]

4 pins, next to the TBI , pass side of intake

 

[mstumpf]

When its idling out of gear will it rev and idle good.
Maybe IAC or tps malfunctioning?

Yeah, when out of gear and idling, it seems to act fine.

 

[mstumpf]

Two questions... the first one is really dumb, so please forgive me:

Are you for sure putting the timing light on cyl 1, rather than cyl 2? Cylinder #1 is left bank (driver side)

What does the injectors' spray pattern look like when it's running? Is it a nice, fine, cone pattern?

There are no dumb questions!

Yeah I made sure I was putting the timing light on the driver's side bank for cylinder one.

The cones have a nice cone pattern.

 

[squaredeal91]

Yeah, when out of gear and idling, it seems to act fine.

Unplug iac when idling and then put it in gear and see

 

[YakkoWarner]

I'm still trying to get my mind around the injectors continuing to trigger once the engine stops. Since the injector pulse comes from the distributor pickup similar to the ignition coil trigger, if the distributor isn't turning they injectors in no way should be firing at all. If something is fooling them into continuing to spray once the engine stops, that same something logically could be playing hell with the spark timing as well.

 

[squaredeal91]

I know you replaced distributor but it's still possible the new one has a problem. So in the beginning.
Was running good daily then wouldn't start for your son. You replaced distributor and it now runs but poorly and now you have different symptoms than before. Maybe point at distributor again? Definitely a weird one man

 

[mstumpf]

Coolant temp sensor? Maybe unplug it and see how it acts

So I unplugged the coolant temp sender which is only 9 months old and the engine seems to stop stumbling and hesitating……the plot thickens….

 

[squaredeal91]

So I unplugged the coolant temp sender which is only 9 months old and the engine seems to stop stumbling and hesitating……the plot thickens….

Sounds like you're getting close. They go bad allot. Keep extra CTS in glove box. Look around for oem brands like Delco or Delphi.

 

[bucket]

Sounds like you're getting close. They go bad allot. Keep extra CTS in glove box. Look around for oem brands like Delco or Delphi.

The original GM CTS's didn't go bad a lot. Just on occasion. The replacements these days tend to suck.

 

[squaredeal91]

The original GM CTS's didn't go bad a lot. Just on occasion. The replacements these days tend to suck.

I meant what you said but wasn't clear lol. I've gone through lots of cheap ones in the past from the auto parts store.
Oem parts are bound to last longer has been my experiences. Especially electronics.

 

[90Supurban]

Unplugging the coolant temp sensor defaults to -40 degrees, I believe? At the very least it will throw it into open loop, but also richen it up just based on what it thinks the temp is. Doesn't necessarily mean the sensor is bad. Running richer, or just being in open loop, could be masking something else. Skewed O2 sensor pushing it lean? Something still wrong with the timing that is masked when its richer (CTS unplugged)? Do you have access to a scan tool that will read data from this ancient stuff?
In a previous post, when you unplugged the coolant temp sensor, it didn't change anything. When it is running, make sure both injectors are firing. Sometimes those connections get splayed and make bad/intermittent contact. Could be firing on 1 injector intermittently or something.

As someone else mentioned, you could have bad NEW parts as well. Victims of shoddy aftermarket quality when there is no other alternative for us.