My TBI has developed an annoying surge at idle and at low throttle in closed loop. When cold and still in open loop the engine runs normally. Once in closed loop at idle the engine will slow until it almost dies, then surge back. With air filter removed I watched the injectors while this happened. The fuel spray slacked off until the the engine almost died when they would squirt more fuel to keep the engine alive.

If I'm holding a steadyspeed at low throttle position I'll hear the exhaust note die out and power will fade away. With my open element I can hear the TBI sucking air, and as I slowly increase throttle the hissing grows louder with no return of power or of the exhaust note. Beyond a certain increase in throttle position the injectors come back to life and the power and exhaust sound is back, but if I hold the throttle steady at that point it will again fade within a couple of seconds until I again increase throttle. As you can imagine this makes driving smoothly damn near impossible. WOT is unaffected.

The computer is displaying no codes. I pretty much eliminated any TBI mounted sensor as the culprit by replacing my TBI with a spare I had lying around. There was no change.

Do I have a goofy ECM or is there something else I need to look at?

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Member Southern California 3rd Generation F Bodies
Co-President Golden State 3rdgens
AOL IM: Andy89RS

 

sounds O2 related. like its dying and giving a really slow reading. either that or a vacuum leak. small one. im having the same thing start to happen, especially as it gets colder. i think ill replace the 02 when i yank the cat off.

 

Could be a voltage drop. In open loop the car runs a little rich and so the idle will be higher for obvious reasons.
Other than that I don't know what to tell you. Have you checked your spark plugs after it's been sitting with that crappy idle? That'll give you an idea if it's running lean/rich and maybe time for a new o2 sensor.

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, Jon (350 TBI!)
91 Red My website

 

I have the same problem!!! I had two vacuum leaks that were fixed but it still does it. It idles fine cold but then surges and almost dies when it heats up. I also have a knock. The o2 sensor and plugs are pretty much new (about 3000 miles on them) but I still have this probelem. I also changed all the electrical sensors (TPS ,ect) and the TBI unit but to no avail. Could I have a voltage problem? When I did have the vascuum leaks I was running WAYYYYY rich, could my o2 sensor just be plugged up? This is driving me crazy.

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1990 RS 305 TBI T-5
.5" turbocity spacer
Edelbrock TBI intake
180* stat
Summit 14X3 OpenElement W/k&N
Hooker 3" Areochamber
MSD - Wires, Cap, Rotor, Coil
Bosch Platinum +4 plugs
Metallic Red w/28,000 Pampered miles
(Still have the original wiper blades)

 

I guess I should have mentioned I pretty much ruled out the O2 sensor as well. It had a relatively new Bosch sensor and I replaced it with another one with no improvement. I'll get a bottle of propane and search for vacuum leaks...

 

Same thing happened to me after I installed my headers. Turned out to be my O2 sensor, though.

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1992 Camaro RS (Auto) 5.0L TBI
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Performance mods
NOS (125 HP shot)
Dynomax cat-back exhaust
Hedman headers
K & N open element/ X-Stream lid
MSD 6A ignition
MSD 8.5mm plug wires
LT1 camshaft
Soon to be installed:
Edelbrock intake manifold
B & M 2400 RPM stall torque converter
Trans Go shift kit
World Products Torquer heads

Audio
Sony Xplod CDX-M610 head unit
Pioneer 2-way 4x6 front speakers
Pioneer 3-way 6x9 rear speakers
12 inch Pioneer VCCS PRO subwoofer
QLogic sealed box
Kicker ZR360 amplifier
Lightning Audio 1 farad capacitor

Other
Macewen White Faced Gauges/Shift overlay
A-pillar gauges (Phantom oil pressure, Air/Fuel)
180* thermostat
Window Tint

 

Replace your Pickup Coil, or test your TPS circut, one test probe to a signal wire and one to a load wire, you should read 5 volt, with ignition on, then do a Resistance test, only this time one probe to a signal and one probe to the ground wire, Resistance should increase smoothly, if not most likely your sensor or circut is shot, and always check the obvouis

 

maybe your knock sensor is reading false knock and trying to retard your timing so much that its hurting idle.