A minor problem?

[shawnboy]

For the first 10 or 15 minutes the truck runs fine. But after it warms up there is a noticable hesitation if moderate to hard throttle is applied upon take off. Also at highway speed when downshifting from overdrive to drive then accelerating it seems like it is not able to increase rpms but sounds like it is choking.
What I've done so far:
new wires and new plugs, properly gapped.
new cap and rotor.
no signs of a vacuum leak(all new lines)
set timing to zero with comp discoed.
installed new coil.
filled up with 91 octane and really expensive fuel treatment.
changed fuel filter.
inspected fuel lines and all visably ok.
fuel pressure is 11 - 12 psi
no trouble codes.
This is a 1990 Jimmy with a 5.7 motor
Any tips would be greatly appreciated.
Shawnboy.

<font color=red>If you are having too much fun it's probably illegal.</font color=red>
<font color=red>Because I, Am, Canadian!!!</font color=red>

 

[txbartman]

Not sure on a comp controlled engine, but 0 degrees timing would make a non-comp controlled motor really have problems. Mine says 4 deg BTDC and I have mine set at 6-8 BTDC.

Brian
Check out <a target="_blank" href=http://tx85gmcguy.alloffroad.com>My Jimmy</a> with all her projects!

 

[shawnboy]

Mean timing on a comp cotrolled vehicle is to be set at zero. The comp does the rest. You have a pretty sharp looking rig, Brian.

<font color=red>If you are having too much fun it's probably illegal.</font color=red>
<font color=red>Because I, Am, Canadian!!!</font color=red>

 

[Stoopalini]

Set timimng to 0'? Have you tried giving it 2-4' of advance yet? I thought the 350 was supposed to be advanced some from the factory? (I could be wrong)

Anyway, from your 10-15min statement, it sounds as if the truck runs fine in open loop mode, but when it reaches closed loop, it has problems.

There is a guy over on the Win ALDL Page

Good luck, I hope I've helped in some way ........

Thomas.

-- '84 1-Ton Blazer --
When the goin' gets tough,
the tough go 1-Ton

 

[txbartman]

Thanks for the clarification. I thought it might be something like that for comp controlled engines. That's why I stated my caveat. Maybe, just maybe, your carb is loose? I have heard of strange problems occurring when the base of the carb is not fully secured.

Thanks on the rig. It gets its first real test this weekend since installing the new engine. I will be competing in a local competition in the "Wild" class. I am looking forward to see how she does in the obstacle course and the mud bog. Should have TONS of pics come Monday!

Brian
Check out <a target="_blank" href=http://tx85gmcguy.alloffroad.com>My Jimmy</a> with all her projects!