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89 TBI 5.7L cough ?

R72K5

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i know locally of an 89 with TBI 5.7L in it and sometimes upon acceleration it will cough out the top end once or twice, pretty much only from dead stop normal acceleration

any idea what might cause such ?
im gonna go with new wires and check manifold vacuum with the guage


also what things can i do or check out on the engine to help it along ? already did replace the plugs and filters.

thanks
 

pauly383

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You say through top end, as in throttle body? Timing perhaps /forums/images/graemlins/thinking.gif Disconnect the wire to distributor and check it. /forums/images/graemlins/k5.gif
 

R72K5

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[ QUOTE ]
You say through top end, as in throttle body? Timing perhaps /forums/images/graemlins/thinking.gif Disconnect the wire to distributor and check it. /forums/images/graemlins/k5.gif

[/ QUOTE ]

yep out the TBI backfire pop on acceleration sometimes, now and then only under load.

check it in what way with wire disconnected ? you lost me. hehe
im used to wrenching on carbureted v8 engines, these TBI ones have a wierd HEI and just arent the same as im used to,

thanks
 

pauly383

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[ QUOTE ]
check it in what way with wire disconnected

[/ QUOTE ]

There is a wire connector on side of distributor . This runs to computer stuff, to advance or retard. You must pull this before setting base timing. /forums/images/graemlins/k5.gif
 

4xcrazy

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Yeah i have heard of people on here saying to disconnect a wire or something going to the distributor, /forums/images/graemlins/thinking.gif but everytime i disconnect anything ay all from the dist, it won't fire at all /forums/images/graemlins/dunno.gif

It's supposed to be a way to make sure the base timing is set at 0 degrees, haven't messed with mine anymore yet though, as i got it running real good with out doing this, just took alittle longer i would imigine. /forums/images/graemlins/doah.gif
 

4xcrazy

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[ QUOTE ]
[ QUOTE ]
check it in what way with wire disconnected

[/ QUOTE ]

There is a wire connector on side of distributor . This runs to computer stuff, to advance or retard. You must pull this before setting base timing. /forums/images/graemlins/k5.gif

[/ QUOTE ]

Not on these TBI's Paul, they are solid connectors with multiple wires going to them, if you pull either of them the whole thing won't fire at all,
There's supposed to be a wire going to the dist plugs somewhere on the firewall, that supossedly has a quick disconnect on it, but i have yet to find it. That is "supposedly" the wire you disconnect for base timing check.
 

pauly383

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Thanks for the clarification TJ. I heard it on here before, but it does sound like timing. /forums/images/graemlins/k5.gif
 

HarryH3

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You'll be looking for a tan wire with a black stripe that has an inline WeatherPack connector. /forums/images/graemlins/cool.gif
 

4xcrazy

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[ QUOTE ]
You'll be looking for a tan wire with a black stripe that has an inline WeatherPack connector. /forums/images/graemlins/cool.gif

[/ QUOTE ]

/forums/images/graemlins/woot.gif THERE IT IS !! /forums/images/graemlins/woot.gif
 

fortcollinsram

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Yep, what harry said! It is on the firewall under the brake-booster! Just disconnect it, start up the truck, set base timing to 0* and turn the truck off and reconnect...If it is still missing after you correctly set timing, do a basic tune up; cap, rotor, plugs, wires...Should take car of any misses that could be ingnition related..

Chris
 

R72K5

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[ QUOTE ]
[ QUOTE ]
check it in what way with wire disconnected

[/ QUOTE ]

There is a wire connector on side of distributor . This runs to computer stuff, to advance or retard. You must pull this before setting base timing. /forums/images/graemlins/k5.gif

[/ QUOTE ]

ok, now i gotcha, yeah instead of having to pull a vacuum advance hose you have to unplug the wire since these are electronic advance, yep.

thanks /forums/images/graemlins/laugh.gif
 

R72K5

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i replaced the cap and wires and i found one big problem, #5 wire was almost completely ripped apart near the boot at the plug end of the wire, /forums/images/graemlins/shocked.gif the wires were the original GM numbered ones with wire loom wrap and all the clips intact and the whole deal,


the thing is 3.42 axle and 700r4, that first gear is extremely quick, then it kinda doesnt have any power to get going good in second gear and after unlesss you really really get on the pedal hard excessively, runs good but seems like it doesnt put out the low end torque it should have

also i went through and tightened up all the TBI torx head screws and the three 1/2" TBI unit mounting bolts, everything was loose, some were even finger loose.,

i see the same thing happen with carb screws so thats why i thought of checking the TBI unit screws.

apparently this same problem exists with TBI units as did with carbs


engine is doing better now, just wonder about the lack of torque it seems to produce

but then it does have 170k on it, and blue smoke puffs now and then lower RPM

thanks
 
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