1991 chevy 1500 5.7 tbi erratic idle

[tpulliam79]

well I am going to check everything I can again friday and from there figure out if the truck is going to the muffler shop , or if im going out and buying more parts, both need to be done just which one now which one in two weeks... working on a very structured budget, especially with all that is coming up.
I have to drive the truck about 300 miles tomorrow so I will see how it goes and then decide...

[tech129]

do you know if your running the stock cam for this truck ? im using an rv cam 204/214 in my 94 ecsb 4x4 and my blm is at 95 and my idle surge after a few secs let me know tech 129

[bowtiejack]

couldn't read thru all these posts but the cam guy was on the right page. sounds like the computer can't keep up with the readings for fuel management, pardon me if you covered this but after timimg check and fuel pressure constant( once it was the fuel filter) i normally go from tps to the ecm inside the distributor . back to the cam dude. if you made performance upgrades like a cam,heads,etc. it might need a new chip-mines from fastchip.com but there are better/more expensive chips out there. anyways, if i was a help-great, if not and somebody already covered this -sorry.

[tpulliam79]

Originally Posted by bowtiejack

couldn't read thru all these posts but the cam guy was on the right page. sounds like the computer can't keep up with the readings for fuel management, pardon me if you covered this but after timimg check and fuel pressure constant( once it was the fuel filter) i normally go from tps to the ecm inside the distributor . back to the cam dude. if you made performance upgrades like a cam,heads,etc. it might need a new chip-mines from fastchip.com but there are better/more expensive chips out there. anyways, if i was a help-great, if not and somebody already covered this -sorry.

so are you saying you also think the cam could be suspect? the small block and cam have just over 30000 miles on them

[tpulliam79]

bump

[tpulliam79]

well the truck drove great on the 350 mile trip , got 17 mpg, ran very smooth while running except that it felt kinda doggish at higher power, also the cruise control kicked off and wouldn't come back on, and anytime i gave it more than 3/4 throttle it would stick and i would have to nail the gas pedal a few times until it would let off? once i get my little one off to school I'm going to check some things, I was thinking fuse for cruise control and throttle cable for the sticking acceleration....any other ideas?

[bowtiejack]

if it was the cam , it would have idled erratic it from the start. the computer chip can only read so fast and make adjustments to the fuel delivery. you can put a dramatic cam inside that would run like greased lightning but wouldn't idle fer sh*t .so if the engine idled fine when the cam/heads went on , that ain't it.when you get a chance. get the engine up to temperature. take some carb cleaner and spray some down the two sides,front and rear , of the intake where it mates to the engine deck. any stumple or rise in rpms would be a gasket leak. use the same method around vacuum lines and its connections. don't get liberal, just enough to check for leaks. let me know what happens and we'll go from there.i'll try to check back regularly to see how its going .

[kevinschoeneman]

Try pluging the vac line to the EGR after the moduel, it worked for me , tho couldn,t tell you why

[bowtiejack]

the egr , behind the tbi on the passenger side , has a baffle on the underside should flex in and out helping to modulate the idle. if it sticks or doesn't suck in and out, it will cause a rough idle but i believe it will flash the check engine lite as it is part of the emissions . to replace it, get the long model number off the original because there are alot of different versions thru out model years.

[tpulliam79]

well havent had time or money for awhile but now i may start trying again.. now at cold startup the engine cuts out or misses real bad goes away after it warms up but then the idle is still eratic at idle? almost feels like a timing issue but i dont know any suggestions?

[NEUMANNZZ]

did you ever check the timing?

[tpulliam79]

its been absolutely nuts here but hopefully tomorrow i can go get a timing gun and check it out, but the last time it was at a mechanic they checked it and said it was fine but I dont recall it jumping around after we hooked the est wire back up

[NEUMANNZZ]

definitely check timing and if it advances with est plugged in.
with the est wire disconnected timing should not be erratic.

also if the engine runs good with the est wire disconnected check the pick up coil. test here:

http://www.autozone.com/az/cds/en_us...rInfoPages.htm

[tpulliam79]

well ended up taking it to a different mechanic and they found that the intake was still leaking, so much to my distress I had to call the other shop where I just paid to have the intake done, he agrees to fix it again but still says its the block or possibly a bad intake , the other shop gave me a free known good intake off one of the techs trucks so that way if this guy wants to say its the intake I have another there already...what does the block have to do with the intake gasket doesnt the intake bolt to the heads not the block? is there anything that could be mistaken for an intake leak?
the leak is at the passenger side rear corner

[NEUMANNZZ]

maybe they want to sell you a new engine.

[tpulliam79]

thats what the mechanic im taking it to says but i what does the shortblock have to do with the intake gaskets? even if something was wrong with the shortblock how does that affect the intake leaking?

[NEUMANNZZ]

unless they did a compression test, it wouldnt effect the intake to block. if they didnt put a big enough bead of rtv then you would just have oil leaking.

[tpulliam79]

he says he will only fix it once because its the wrong short block but shouldn't they be able to fix the intake either way

[tpulliam79]

is there any reason the intake wouldnt seal because of the different shortblock?

[tpulliam79]

gotta take the truck to the shop in a bit . is there any reason the shortblock from the 78 with the 91 heads would cause the intake not to seal?