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1990 5.7 350 chevy RWD C1500


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Jonathan Gibson
Novice

Dec 12, 2013, 5:53 PM

Post #1 of 12 (1249 views)
post icon 1990 5.7 350 chevy RWD C1500 Sign In

I NEED HELP!!! My truck has a shake.. it runs smooth till you put it in drive. once you take off it shakes and acts like its choked out or restrained. and when you get in it hard it acts like it can't pick up or get the air or fuel it need and then shifts hard along with the hard shake... I have grate fuel pressure oil pressure and not over heating.. I've replaced the fuel filter under the frame rail new fuel injections and filters new plugs plug wires set timing new distributor cap new throttle positioning sensor the trans has been rebuilt new torque converter and all new fluids.. I'm at a lose here its driving me nuts I NEED HELP before I go broke and crazy


(This post was edited by Jonathan Gibson on Dec 12, 2013, 5:59 PM)


Discretesignals
Ultimate Carjunky / Moderator
Discretesignals profile image

Dec 12, 2013, 6:08 PM

Post #2 of 12 (1227 views)
Re: 1990 5.7 350 chevy RWD C1500 Sign In

How many miles on this engine? You should first perform a compression check. Make sure the battery if fully charged, the distributor connector is unplugged, and you have the throttle wide open when you do your compression check. Write down your numbers and post them in here.





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.


Jonathan Gibson
Novice

Dec 12, 2013, 6:13 PM

Post #3 of 12 (1222 views)
Re: 1990 5.7 350 chevy RWD C1500 Sign In

the compression is good.. I just can't find why its acting smothered out could the o2 sensor make it do this?? or could it be the mass airflow or map??

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Discretesignals
Ultimate Carjunky / Moderator
Discretesignals profile image

Dec 12, 2013, 6:16 PM

Post #4 of 12 (1218 views)
Re: 1990 5.7 350 chevy RWD C1500 Sign In

So you tested the compression already? What numbers did you get?





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.


Jonathan Gibson
Novice

Dec 12, 2013, 6:20 PM

Post #5 of 12 (1216 views)
Re: 1990 5.7 350 chevy RWD C1500 Sign In

not sure on the numbers but the man I had look at it said compression and fuel pressure was vary good that it could be my throttle position sensor took it home and replaced it and same stuff


Discretesignals
Ultimate Carjunky / Moderator
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Dec 12, 2013, 6:27 PM

Post #6 of 12 (1212 views)
Re: 1990 5.7 350 chevy RWD C1500 Sign In

Just wondering because if you have compression problems, that will affect everything else. The fuel injection system on that engine relies on engine vacuum to calculate injection and ignition timing. If you have low or erratic manifold vacuum because of engine mechanical problems, you be chasing ghosts replacing sensors.





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.

(This post was edited by Discretesignals on Dec 12, 2013, 6:29 PM)


Jonathan Gibson
Novice

Dec 12, 2013, 6:35 PM

Post #7 of 12 (1207 views)
Re: 1990 5.7 350 chevy RWD C1500 Sign In

if its a vacuum line wouldn't it cause the truck to rev faster or almost die??


Discretesignals
Ultimate Carjunky / Moderator
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Dec 12, 2013, 6:39 PM

Post #8 of 12 (1205 views)
Re: 1990 5.7 350 chevy RWD C1500 Sign In

A vacuum leak will probably cause high idle, but shouldn't cause it to die or bog on acceleration.


If you are sure you have good fuel pressure/volume and the engine is mechanically sound, testing for excessive back pressure would be something to check out. Does this have headers/dual exhaust or is it on manifold and Y pipe?





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.

(This post was edited by Discretesignals on Dec 12, 2013, 6:42 PM)


Jonathan Gibson
Novice

Dec 12, 2013, 6:46 PM

Post #9 of 12 (1201 views)
Re: 1990 5.7 350 chevy RWD C1500 Sign In

yes I have a set of custom hooker headers that go into an x pipe then into to 44 flow masters that dump half bed


Discretesignals
Ultimate Carjunky / Moderator
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Dec 12, 2013, 6:50 PM

Post #10 of 12 (1198 views)
Re: 1990 5.7 350 chevy RWD C1500 Sign In

Cats are gone? Are there any other mods on this engine?





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.

(This post was edited by Discretesignals on Dec 12, 2013, 6:50 PM)


Jonathan Gibson
Novice

Dec 12, 2013, 6:58 PM

Post #11 of 12 (1195 views)
Re: 1990 5.7 350 chevy RWD C1500 Sign In

high rise intake new rods valves rockers springs 292 thumper comp cam iron eagle crank and punched 30 over with a performance throttle body and 40 lb injectors I've done all of this last year and the truck ran like a sewing machine till three days ago


Discretesignals
Ultimate Carjunky / Moderator
Discretesignals profile image

Dec 12, 2013, 7:07 PM

Post #12 of 12 (1189 views)
Re: 1990 5.7 350 chevy RWD C1500 Sign In

Could be a misfire causing your issue if it is shaking and lacks power. If you brake torque the engine, can you duplicate the misfire/shaking? With the big cam it is kind of hard to pick out misfires at idle. You could do a power balance test by disabling spark for each cylinder one at a time while the shaking is going on. The cylinder that doesn't make a difference is the one that is missing.





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.






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