Ok, I have a '88 silverado. I know its not a third gen, but we are all members of the TBI family right...j/k. This might be long, but please stay with me. Anyway, Im running a 670 Holley on a Street Dominator Intake. I got a crap load of other mods, if you think you'll need them, please post then I'll list them all later. Ok, when I start it up in the morning, the engine is cold and it runs pretty fast... got a third gear chirp once. As the engine warms up, it bogs and backfires through the TBI. Finally about the time I'd like to drive it into a tree, it warms up all the way it stops backfiring and bogging. But I still notice that it is pretty lean on the top end. I'll punch it at 70 mph and it barely speeds up. I got heads with 2.02/1.60 valves and 3.08 gears so I know I got some power up top. Anyway, these are all symptoms of not enough fuel right? But I don't know how to fix it. I want it to run like it does when the engine is cold. I know the timing changes as the engine warms up. Should I bump up the timing, its set at 0 degrees now, or should I bump up the fuel psi, I think its at stock psi (14-15 psi)? And is there anyway way change all of this acurately without a scanner? Thanks

 

Get a scan tool. It really is the only way to check for gross/across the board or certain zones of fuel problems. You gotta do that with all your config changes.

I assume/hope that you are not running the stock PROM...???

 

prom could definatly be a bad guy in your system. Boosting pressure never hurt anything but mialage if you are already lean.

Thats the first thing i would do. My car did that too since i adjusted the pressure the wrong way. I thought damn it starts right up now in the winter, but sure didnt run right after that until it was hot. boost it, it should help, then check your plugs.

 

bump up the fuel pressure a bit. leave the timing where it is at until you are sure you have enough fuel.

lata
tim

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91 Camaro RS-LO3,Auto.
14.215@94.30 w/ 1.917 60'

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Thanks for all of ya'lls help. I guess I'll have to go back to Houston on the weekend to get the fuel pressure bumped up a bit, because theres no way I can afford a scanner on a college budget. I'll go ahead and list the rest of my mods just to clear up any guessing.

World S/R Torquer Heads
Crane Compucam 2020
Crane 1.5 roller tip rocker arms
Edlebrock TES Headers
True dual exhaust w/ 2-1/2" pipes, 2 hi-flo cats, 2 dynomax mufflers
Jet Stage 2 chip
flat top pistons

 

Hey, if an oxygen sensor goes bad what happens? Does the SES light come on or what? Another thing, if the oxygen sensor IS working then fuel pressure shouldn't be the problem for backfire and major bog like that. The O2 sensor would tell the chip to fire the injectors faster or slower depending on the condition of fuel:air ratio. Tweaking the fuel pressure does do wonders for throttle responce and other things but I don't think it would be that big of a deal if everything is working. Definatly get a scan tool hooked up and play with the fuel pressure just cause. How many miles are on the holley TB unit? I know that the stock injectors from GM are toleranced better (that's what I've been told) and that the holley units come with cheap chrysler crap.

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, Jon (91 RS too many mods to list)
Dale Earnhart, you have done so much, you will be missed.