Hesitation at partial throttle

[red_barron]

My truck is a 94 with a rebuilt and bored over 350 and a slipping 4l60e. When i try to cruise with a granny foot its like the truck has no power and hesitates kind of, but when i give it more throttle it jumps up and acts normal. Sometimes at idle isle act like the idle is too low and almost die but i had ti raise my idle because of that problem. This summer i plan on rebuildin the top end with alum heads, headers and everything and possibly convert to carb. I drive the truck every 3 weeks cause i work 14/7. Whata you guys input on this?

 

[trx88]

check your fuel pressure should be high 50's to 60 primed and ill tell you this ive heard of guys having 60 psi primed and still no low demand flow, fuel pump.

 

[Chris]

Uh, no. Stock small block TBI systems only run at 11-14psi. It still needs to be checked though. I've seen broken regulator springs cause that. Has the TBI unit been rebuilt as well?

 

[WFO4X4]

check your egr valve

 

[koke]

sounds like a possible timing issue, EGR is only "supposed" to open at highway speeds, and as for fuel pressure, yea right around 11-14 pound mark but i have seen 20 on a tbi, kinda hard to tell by just what the problem is and not knowing what the A/F ratio is doing at said idle, wanting to die-throttle comes out of it

 

[DRAGGIN95]

I would use a live data scanner and check out the TPS, and possibly also replace the IAC valve for the idle issue. One other thing if you haven't ever rebuilt your throttle body then you should, it makes a big difference!

 

[WFO4X4]

sounds like a possible timing issue, EGR is only "supposed" to open at highway speeds, and as for fuel pressure, yea right around 11-14 pound mark but i have seen 20 on a tbi, kinda hard to tell by just what the problem is and not knowing what the A/F ratio is doing at said idle, wanting to die-throttle comes out of it

yeah, egr is only open at hwy speeds but if it's bad it screws up the way the truck runs at ALL speeds... all the other stuff that has been mentioned is valid also.

 

[koke]

haha yes this is why i said "supposed" but even with a stuck open EGR there is pretty little exhaust that recirculates on these pickups, and yes everything else is valid, but i was figuring with a rebuilt block that the timing could be off, some people (like myself) get excited and time by ear just to take er' out!!

 

[WFO4X4]

haha yes this is why i said "supposed" but even with a stuck open EGR there is pretty little exhaust that recirculates on these pickups, and yes everything else is valid, but i was figuring with a rebuilt block that the timing could be off, some people (like myself) get excited and time by ear just to take er' out!!

yeah, biggest reason i mentioned the egr is i just fixed my 93 that was doing the same thing. i also thought fuel pressure, vaccum leak, electronic miss.... PCM issues, and it was the EGR. it doesn't happen so much on vortec motors like it did the old style tbi 350's. it's a pretty cheap fix and in my exp worked like a charm.

 

[koke]

so in other words deleated? lol or did you clean/replace? kinda curious because yes tbi's are very famous around where i live to take a dive