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350 tbi dies/stalls at idle/ shifting into reverse

Was this ever resolved? Sounds like it could be an IAC issue. May be on the way out. Before it dies, does it give you any indication it's about to? If you give it part throttle, does that keep it from dying? Troubleshooting TBI get's old fast and expensive faster.
 
The_Tomato said:
Was this ever resolved? Sounds like it could be an IAC issue. May be on the way out. Before it dies, does it give you any indication it's about to? If you give it part throttle, does that keep it from dying? Troubleshooting TBI get's old fast and expensive faster.
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Not yet. With the truck down for suspension/steering/exhaust/paint upgrades, hasn’t been an issue. But I think it’s as you describe: there is a brief margin of realization that the engine is about to die, and I mean brief. If I catch it and give it some throttle, seems like it keeps it alive. But it’s a quiet engine, unlike my diesel, so catching it is difficult. I have suspected a failing TBI also. Call me ignorant, but what is IAC?
 
AugustDiesel said:
Not yet. With the truck down for suspension/steering/exhaust/paint upgrades, hasn’t been an issue. But I think it’s as you describe: there is a brief margin of realization that the engine is about to die, and I mean brief. If I catch it and give it some throttle, seems like it keeps it alive. But it’s a quiet engine, unlike my diesel, so catching it is difficult. I have suspected a failing TBI also. Call me ignorant, but what is IAC?
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Sorry, Idle Air Control. It's a small valve on the throttle body itself that meters air entering the engine at idle.
 
The_Tomato said:
Sorry, Idle Air Control. It's a small valve on the throttle body itself that meters air entering the engine at idle.
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No worries. Diesel fuel flows through my veins so this gas engine stuff has a learning curve. I’ll add the IAC to my list of things to look into.
 
AugustDiesel said:
I mean any option for improving. What do ppl do with these 350 TBIs - excluding swapping the engine.?
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Honestly, I've been trying to do homework on this for a loooong time. I'll speak a bit from my personal experience- when the TBI is in good form and properly functioning, it's honestly a pretty pleasant driving experience. Snappy throttle response, good low-end torque. From everything that I've seen though, upgrading them is a chore. You have a few options:

1) The Holley upgraded throttle body and injectors
2) Using 454 tbi injectors
3) Porting the throttle body itself?

Potentially then building a motor, getting the PROM flashed and then hoping the specs you provided to the programmer work well. It really seems to me like the easiest thing to do would be buy a 4bbl intake manifold with the vortec-style bolt pattern and throw a Holley Sniper efi on there with a HEI-style distributor. My plan as of now is either that or an LS swap, but my truck runs fine so I AIN'T EFFIN WITH IT haha.
 
I'll add that whenever my friend, who has a carbureted 84 K5, drove my truck, he would comment on how even though the trucks are similar, mine felt more "modern" to drive. I chalk that up to the TBI system. I really do think it drives great in stock form.
 
The_Tomato said:
I'll add that whenever my friend, who has a carbureted 84 K5, drove my truck, he would comment on how even though the trucks are similar, mine felt more "modern" to drive. I chalk that up to the TBI system. I really do think it drives great in stock form.
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Agreed. I’ve been really please with the power output and drivability of this 350 in stock form, aside from the cutting off issue. I’d like to hood off on doing any major modifications to it, because, to be honest, when the time comes to replace the motor, it’ll likely get a diesel of some sort.
 
AugustDiesel said:
it’ll likely get a diesel of some sort.
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Shocker there :haha:You said it's not throwing any codes? OBD1 is.... dated, to say the least. But it's still a computer and can tell you if it's hurting in some ways. I swear it sounds like an IAC issue.

1989 CHEVROLET V1500 SUBURBAN 5.7L 350cid V8 Idle Air Control (IAC) Valve | Shop Now at RockAuto

Fuel & Air Parts and More for Your 1989 CHEVROLET V1500 SUBURBAN at Reliably Low Prices. Fast Online Catalog. DIY-Easy. Your Choice of Quality. Full Manufacturer Warranty.
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RockAuto might just be your friend on this one
 
The_Tomato said:
Shocker there :haha:You said it's not throwing any codes? OBD1 is.... dated, to say the least. But it's still a computer and can tell you if it's hurting in some ways. I swear it sounds like an IAC issue.

1989 CHEVROLET V1500 SUBURBAN 5.7L 350cid V8 Idle Air Control (IAC) Valve | Shop Now at RockAuto

Fuel & Air Parts and More for Your 1989 CHEVROLET V1500 SUBURBAN at Reliably Low Prices. Fast Online Catalog. DIY-Easy. Your Choice of Quality. Full Manufacturer Warranty.
www.rockauto.com

RockAuto might just be your friend on this one
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Thanks for the tip. Looks easy to replace?
 
When you pull the IAC have a wire pipe brush on hand and a couple can's of brake/carp clean. there is a passage the IAC pintle opens and plugs, it gets sluggy so you will want to clean it. Also the use the brush on the throttle bore near the throttle plates that gunks up too.

I fact it may be your problem. If it were mine I pull the TBI off, clean the throttle bores the IAC passage and pintle. Put a drop of light machine oil on the pintle plunger threads.
Put it on start up truck let it get warm, then re-snuge the TBI bolts.
It really is a simple system. Keep a clean fuel filter inline, good cap and rotor, weakest link in my opinion. The truck will run well for years.
 
AugustDiesel said:
I mean any option for improving. What do ppl do with these 350 TBIs - excluding swapping the engine.?
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You aren't going to do any better than properly working TBI. The power limitation on these is a package deal...heads, cam, intake, throttle body, exhaust, etc.

The solution is to change all that. Changing the induction system alone won't change the limitations of the TBI engines in OEM form.

They work, they work good, and they generally last. They don't make a ton of power, but they weren't designed to.

Very easy to make mods, but the induction system is certainly not where you'd start IMO. *Except* being able to tune an aftermarket system significantly easier. Although I still don't see them working better than a tuned TBI system.
 
Good news, apparently I'm smart enough to bookmark links to automotive resources!! If you want a full comprehension of your wife's TBI system and you have 15-30 minutes on your hands, check out this link. Takes you through the whole system basically.


The biggest thing that helped me was the chart on page 2 that shows all the inputs and outputs for the ecm. Take a look!
 
The_Tomato said:
Good news, apparently I'm smart enough to bookmark links to automotive resources!! If you want a full comprehension of your wife's TBI system and you have 15-30 minutes on your hands, check out this link. Takes you through the whole system basically.


The biggest thing that helped me was the chart on page 2 that shows all the inputs and outputs for the ecm. Take a look!
Click to expand...

I’ve ordered a new IAC and have it in hand. Hard process to replace?
 
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