tbi issues, on my 88 gmt400

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RetroC10Sport

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Isn't there a fuel pump prime somewhere on these trucks? I need to see.

Guess not. But he should be able to come off the relay with a hot lead.
 
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Jims86

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Isn't there a fuel pump prime somewhere on these trucks? I need to see.

Guess not. But he should be able to come off the relay with a hot lead.

Yup, its pin G in the ALDL connector, not all of them had it. otherwise, look for a red pigtail coming off the Fuel relay plug.
 

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ha anybody got a computer I can swap in to try?

I unhooked the dist. computer control thing, the timing connector as I all it, drove it, the bad backfire/cough/miss thing was back under throttle, advanced the dist. made that go away but started stalling out changing gears AGAIN, no computer hooked to the dist. So I guess it's elsewhere.

Honestly for me I think my plans may be to just swap it all out for a carb, intake and hei dist.

But if I could find an ecm to try I would try it. I just can't really afford to throw anything at it without it fixing the problem.
 

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ha anybody got a computer I can swap in to try?

I unhooked the dist. computer control thing, the timing connector as I all it, drove it, the bad backfire/cough/miss thing was back under throttle, advanced the dist. made that go away but started stalling out changing gears AGAIN, no computer hooked to the dist. So I guess it's elsewhere.

Honestly for me I think my plans may be to just swap it all out for a carb, intake and hei dist.

But if I could find an ecm to try I would try it. I just can't really afford to throw anything at it without it fixing the problem.

I think PawPaw may have a spare.
 

89Suburban

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Phuckin A right, shoot me your address, I'll take care of ya pal.
 

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nice man...

I'll send ya a pm and we can try it.

anyways tried to check my timing, and the way it was and was running good but dying changing gears, my timing base unhooked was over 14 degrees advanced, the tdc balancer mark was almost pointing straight up to the hood.

I set it back down to zero, no power, no balls just bog and backfire like.

advanced it to the end of my timing mark on the cover and left it there for now.
 

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nice man...

I'll send ya a pm and we can try it.

anyways tried to check my timing, and the way it was and was running good but dying changing gears, my timing base unhooked was over 14 degrees advanced, the tdc balancer mark was almost pointing straight up to the hood.

I set it back down to zero, no power, no balls just bog and backfire like.

advanced it to the end of my timing mark on the cover and left it there for now.

Didjya check fuel pressure? Back fire is lean. Ya have another MAP sensor around to try?
 
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Swims350

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don't have another map, but Fp has and it always around 12-12.5 at the fuel filter.

This thing is almost running right, still has some miss or backfire whatever under a throttle stab, but will melt tires, sometimes, and yes it still dies changing gears, it actually did it a couple times this morning and refired!!!!! I just hit the gas pedal iand it would start, but afterwards it would not refire again, several times.

paw paw is gonna loan me a computer to try and see what happens, if that' s a no go and I can't get a spare map or esc moduel to try, it's carb time for me.
 

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don't have another map, but Fp has and it always around 12-12.5 at the fuel filter.

This thing is almost running right, still has some miss or backfire whatever under a throttle stab, but will melt tires, sometimes, and yes it still dies changing gears, it actually did it a couple times this morning and refired!!!!! I just hit the gas pedal iand it would start, but afterwards it would not refire again, several times.

paw paw is gonna loan me a computer to try and see what happens, if that' s a no go and I can't get a spare map or esc moduel to try, it's carb time for me.
you mean with a " T" at the filter, or just capped directly into the gauge? If direct, that pump should be at 18psi or over. paw Paw may have another map too
 

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Yah I'll add the MAP sensor off the '89 to the package too. It will ship out of here Monday afternoon UPS Ground. I got the ICM off Silvy's dizzy too if you want to try that. Just try and send me back whatever you don't wind up using. Especially if you go to a carb setup.
 

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it was the t fitting onto my actron gauge.

as for whatever I don't use, you got it man was going to anyways.

I don't know if an ICM would help, I got a new dist. and it was complete, so not sure. If you wanna send her go for it, anything I don't use(trying one at a time) I'll be glad to send back, and if I can't fix it then it's going carb and I'll send you back everything.
 

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I got all 3 boxed up and ready to ship. You'll have the tracking number the end of the day.
 

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well I'm down to the ICM now,

tried the computer, thought it would work but same thing, I set the timing back to zero before changing them out, connector unhooked, put in paw paws computer, fired it seemed good, drove it, still falls on it's face, if you drive slow and very gradually feed it the gas it will run ok, anytime you go to fast down with the pedal it just starts to backfire, or miss or just about dies out, I mean just nothing, falls on it's face. Same as with my old computer.

one thing I never checked with my old computer was base timing with the connector plugged in, with pawpaws computer it's way up on initial timing, I mean it was almost pointing straight up idle with the timing connector plugged in.

Then I tried the MAP sensor, haven't drove it but just sitting still in park when you hit the gas it just falls off right off, then trys to pick up, just stab down the pedal and it just bogs down.

I'll have to drive and confirm but it doesn't look good so far.

As of now pawpaws computer and map are on it, and going to change the icm when I get a chance, have to buy some grease for the bottom of it, it's just di electric grease right?

I do have a new tps on it, and it never helped I put it on a few months back, only things not new or changed is the esc module, the IAC, then of course the icm is about 4 years old and was in the dist. new.

I really hav eno idea, kinda leaning towards maybe my injectors are crap or something.

Would it be a fuel pressure reg. diaphram issuE?

it only started this bad miss crap after the throttle body rebuild and mods.

I never touched the timing from before when it ran good, only down side was back then it did still die sometimes changing gear and not refire for a few.

speaking of I'm unsure if either parts change from pawpaw, has fixed or helped the change gear die or not refire issue. I haven't ran it enough to find out.
 

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may end up being on the look out for an old 4bbl intake, be it for 86 and older or the correct 87-95 setup, seen the adapters and tons say they just drilled the 4 center holes to use an older 86 and under intake on the 87-95 heads, also gonna have to find an old crab and hei dist. to go with em.

I'll try the icm first and if that fails I'll track down some carb parts.
 

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Hmmm...this thing is acting like it has 305 injectors. If there was a diaphragm issue, ther would be fuel pouring out of the regulator, and fuel pressur would be way down...like when that rubber line in the tank is shot. Have you checked your valve adjustmets at all since putting the valve covers back on? Have a vacuum gauge? Hell, maybe something crawled down your fuel line when you had it apart, and finally made its way up to one of the injectors.
 

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