TBI diagnosis reminder

[gmbellew]

having weird issues with your TBI? before getting out the parts cannon, follow this advice from the GM Drivability manual before you start in with more complicated diagnostics-->

BEFORE STARTING

This check should include:
• ECM/PCM grounds for being clean, tight, and in their proper location. See "General Information,” Section "1” for location.
• Vacuum hoses for splits, kinks and proper connections, as shown on "Vehicle Emission Control Information” label. Check thoroughly for any type of leak or restriction.
• Air leaks at throttle body mounting area and intake manifold sealing surfaces.
• Ignition wires for cracking, hardness, proper routing and carbon tracking.
• Wiring for proper connections, pinches, and cuts.

and I'll add 2 more things to check -

distributor cap for cracks or any evidence of carbon tracking indicating spark leaving the cap

exhaust backpressure in case the CAT is clogged up, assuming a CAT is still installed.

just posting this up as a reminder. I've had the most issues, and the hardest to diagnose issues, with spark hitting places it shouldn't be the (ECM grounds to the engine) or vacuum leaks from bad lines or bad gaskets.

Start with the basics!

 

[ChuckN]

I don’t know anything about TBI, but that is a great reference. Perhaps this could be a sticky thread, I see TBI questions all the time.

 

[vr1967]

Also, here are the flow charts from the service manual to help diagnose issues

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