Huge Bog

ryan_thompson87 · March 3, 2009

I have got a huge bog every time I push pedal past 1/4 throttle. It will fall flat on its face for 5-10 secs and then off like a rocket. Doesnt do it when shes cold, but once at operating temp awful. Stalls sometimes too if you mat it and don't let up a little bit. Any ideas where to start? 87 Sierra 355 TBI Vortec Heads, GMPP Intake, Cam, Headers, TB Spacer.

kuhl_530 · March 3, 2009

Spark advance may be off... or your timing maybe?

66nova · March 3, 2009

Have had a custom chip burned? Also, what have you done to the fuel system? Any upgrades there...bigger injectors, bigger throttle body, etc.

Timing certainly could come into play. The one thing that sticks out is the fact that it doesn't do it cold. Makes me wonder if it is a lean bog. If that it the case, refer to the first couple of lines of this post.

Mike G · March 3, 2009

I was leaning towards fuel starvation issues, but I am not too savy on the TBI leaning out at throttle up. Could be a fuel pressure issue or injectors.

--Mike

ryan_thompson87 · March 4, 2009

Well to start it's not tuned BUT, I have run it as is for two years with a problem. So far I have ruled out Injectors, Timing, MAP Problem, TPS, EGR Valve, but not the Solenoid. The only test I can find for the ESC, is for the knock sensor, none for the actual module. I have checked for vacuum leaks repeatdly and fix a few very minor ones. I have not yet checked fuel pressure, but it has dual tanks and it doesn't matter which one it's on, so I'm going to rule them out. It has a bit got better, to only a stumble when throttle is given quickly.

ryan_thompson87 · March 10, 2009

Anyone?

Mike G · March 11, 2009

The ESC is a simple replacement item, if that doesn't clear things up, return it to the auto parts store or keep it as a spare. Since you haven't checked fuel pressure, that would be your next logical place to check. I believe that the pressure regulator is at the TBI unit, it would have no bearing on what tank you are running. Have you had any work done to the throttle plate bushings?

--Mike

ryan_thompson87 · March 11, 2009

No, but I have made the regulator adjustable.

ryan_thompson87 · March 18, 2009

Small update. Since the temperature as gone up to above 0 celcius, It has improved drastically, the only time it really stumbles is from a standstill and I put it directly to the floor and I also noticed when lugging it (in this case plaing in deep snow and mud) it doesnt really want to rev it labours quite a bit. Any idea what this could be from that would be effected by the weather that much? Fuel pressure possibly? I may play with the regulator and see it turning it up or down makes much of a difference.