OK new here first off. what i have is a 88 iroc z28 5.7.

what has been done to it so far. replaced all fluids, and filters, plugs, wires, cap and rotor. throttle position sensor, idle air control valve fuel pump and filter. cat is good still too oil pump sending unit. um i think that is all.

the symptons. starts and idles just fine. slowly press the accelerator and reves strong and fine to max. put a load on it and or go down the road and step on it hard she bogs down not going past 3000 rpm. then when i let off the gas pedal a little it goes back to normal. i cant get past 40 mph when stomping on the gas pedal or just easing into it. one goin and in drive if i hammer on the gas it will down shift them just feels like its starving of air or something like that. what do you think might be causing this problem? i have a race i need to win so i need her to run again.

 

Welcome aboard thirdgen.org.

Did you replace the fuel filter?

Check fuel pressure. You likely have a clogged fuel filter or weak fuel pump.

 

I had the same problem in two different vehicles. One was a kinked fuel line, the other was the little rubber hose in between the pump and sending unit. Like Five7kid said its probably fuel.

 

Thanks for the welcome. Yes the filter is new as is the pump. We ant starving for fuel as I can get her to reve up all the way to 7 grand as long as I slowly do the gas. It feels like she is starving for air or not breathing right. I do know we are getting fuel though.

 

ok what about the mass air flow sensor? think that might be causing the problem. that is the only thing that i havent replaced new(used a junk yard one).

also does anyone know of a good place to get one for a good fair price?

 

still need help. anyone else have any ideas?

 

what voltage is the TPS set at? also what brand sensor did you put on it. Ive seen many issues with cheap aftermarket sensors.

 

TPS is set is 6.8volts. Just got whatever it was auto zone had. Should I try a different volt or replace it with another one?

 

the voltage should be at .54 volts if Im not mistaken

 

ok well the instructions said between .5 and .8 so i put it there at .68. acadently put 6.8 for some reason. so i will try to get it at .54? that isnt much of a differece is it? ok so i just tried it out. set it at .542 and still bogging out when i try to get on it. but is fine when sitting still revs right up to max.

 

well thats one issue resolved, did you check your fuel pressure? If im not mistaken the pressure should be 43.5 psi at an idle with the vacuum hose removed from the regulator. Hope this helps.

 

No offense, you said the fuel pump and filter have been changed? Is the filter installed correctly, reversing the flow of the filter could cause fuel delivery issues.

 

oh shoot non taken. i mean silly things have happened before. but im sure its flowing right and i will double check that. hey thats why im here to get help look at things i may have over looked. so i can check that. no i havent checked the fuel pressure yet. need to go to az and rent a pressure checker then i can get back more info to you. also haven replaved the fuel pressure regulator. maybe that could cause it too. i hate getting nickeled and dimed though. i mean the car was a steal for 650 bucks. all it needed was a fuel pump but the guy wasnt mechanicaly inclined at all. talked him down from 3400 to 650 not bad of a deal. all i have to do now is get this resolved and shell run like a top. no rust no dents absolutly beautiful car for the price. ill post pics sometime. thanks again.

 

i had the same thing with my car get to about 3000 and fall on its face and all it was the 02 sensor was bad, it was stuck on lean so there for not getting all the fuel it needed, easy way to see is get a scan tool and see if its going from open to closed loop and make sure your 02 voltages go up and down, hope less helps

 

going to get an 02 sensor today and try to install it if at all possible. mothers day ya know. but yeah she does that falls on her face right around 3 grand or so. ill post up and let you know if that cures the problem. if not then im sure its the mass air flow.

 

well replaced the o2 sensor and that made things worse. now she wont reve up sitting in park unless you just lightly apply the gas and slowly reve it up. so im sure its the MAF. so um anyone live in the hampton roads area virginia that wants to let me use there MAF for testing purposes? or maybe have one for sale? dont wnat to pay the outragous price for a new one. anyone know of a good place to get one on the cheap or have one for sale that would be great.?