88’ K5 TBI - ECU Timing Help

[Charleshugh]

Hey guys, took my K5 to the shop (big regret) and they replaced the distributor on my 350 TBI. He then adjusted the timing to help the backfires. It was sluggish when I got it back and had an engine light, making me think it was retarded (and it was). After dialing the timing back in with my timing light I still get an ECU code and it still sounds sluggish. Yes I disconnected the timing wire to the ECU prior to adjustment.
After getting it back from the shop I drove it for a week and now it cuts off when I give it any gas whatsoever.
I hate to see my baby bed bound.

 

[Wes Harden]

The TBI distributors are weak at best. To honest I never had good luck with anything but a whole GM distributor.

Before we go and condemn this new distributor we need to adress the missfires.

The spark plug wire routing is very critical. keep them away for the smaller distributor wires and the coil. Try not to run the sp wires parallel to each other for more than an inch or two.
Use good spark plug wires, and set your gaps to .035-.040"

Inspect cap and rotor, these are weak too, prob need new once a year depending on total mileage in said year.

I would do a compression test.
Cylinder and valves issue could cuase low power and popping.

Many have found a base timing of 2 or 4 degrees btdc to work well with the tbi engines.
The EST could be getting a false reading from the knock sensor cuasing the timing to retarded while running.

 

[Blue85]

Many new distributors and parts are no good out of the box, so that's one possibility. You must have had some pre-existing issue that prompted the distributor swap, so it may be the same thing as before. What can you tell us about that?

Some things to check:
-Despite best intentions, sometimes the plug wires get installed wrong. Double and triple check. Some combinations can still sort of run. Also verify that the rotor is actually pointing at the terminal for #1. With some issues, the plug wires just get offset by one tower and you don't notice until you start replacing parts.
-Sometimes the balancer slips, moving the timing mark. (There are also some parts mixing that can cause the timing mark to be off.) Verify the #1TDC vs your timing mark using a thread in TDC checker or something simple like a straw in the spark plug hole.
-Check for vacuum leaks all around the TBI.
-Verify that both injectors make a nice cone of fine fuel particles.
-I would use a timing light or spark plug checker to verify strong current in all 8 plug wires. If you have that and verify no plugs are broken or shorted, then the spark *quality* is probably OK. A new distributor *usually* means new plugs and wires, but I've seen plugs damaged on install and some new wires are crap.
-If still no progress, check the fuel pressure (or start there, it's EFI!). There have been a lot of TBI owners on here reporting 10psi or less and drivability issues.