350 TBI questions

BOSOX · Sep 29, 2013

My Juggy has a '91 Burb tbi 350. The previous owner had it rebuilt a few years ago, bored .030 and a rv cam. Block higher headers, 4 wire ( heated)o2 sensor, Howell ECM and harness. It's run rich since I've had it. I've replaced cts, iac, and rebuilt the injectors. Those changes helped it run better, less stalling and better idle. However, it still seems to run rich and I don't get a faster idle at start up when it's cold. A buddy has tried checking for any codes but the scanner won't read it, tried swapping in a chev van ECM and still doesn't read.
I guess a tune up is in order...what else am I missing?

June dog · Sep 29, 2013

Try a new temepture sensor, when they go bad they will idle rich and not run very well. It's a cheap place to start and easy to get to. :****:

muddinmetal · Sep 29, 2013

A good tune up it always a plus, but you can NOT modify a TBI motor and not have a cistom chip burned... unless you like it running like crap. Call or go to TBICHIPS.COM and tell them what you have and be happy to put this junk behind you!

cutngut · Sep 29, 2013

Yup. Wat he said. ^^^^ :dblthumb:

BOSOX · Oct 2, 2013

Ran the same after tune up. Still need to try another cts.
Tbichips.com got some nasty reviews...I know you can't always trust the interweb! I'm trying to avoid the $300 chip anyway...

RustyC · Oct 2, 2013

The TBI ecu's use OBD1 connections at the service connector. To check codes most people use a paper clip or short length of wire to connect two of the terminals. I can't remember off hand which two to connect , google will know. OBD2 scanners won't read.
Do you know if the ECU has the chip from Howell in it?
The TBI system will run in open loop ontile the engine gets warm. That means it is not reading the O2 sensor. If you are rich on startup it is programming, restricted air to the engine, worn injectors, possibly high fuel pressure, idle air solenoid.

For what it is worth. I run the same system in my Jeep. If I dissconnect the batteries it runs really rich on startup, then as the engine warms up it goes into closed loop and reads the 02 sensor and coolant temp. and adjusts to run correctly. If I ride for a while and crank the engine a few times the system seems to work flawless after that point.