I have an 87 IROC with the 5.7 TPI motor. The car hesitates when I floor it off idle then has good power after the initial hesitation. Any ideas of what could be causing it?

 

Improper tuning. There is a thing called pump shot, it is the initial fuel added to when you floor it.

There could be a problem. If you are not getting full charge from the alternator, bad ground, or loose battery connection would also cause it. There are many reasons why you feel hesitation

Have you done anything to try and fix this? Is this a new problem, has it ever happened before with this weather, etc., etc.

 

I have the same questions that Maroon posed regarding when it started (always,,, or after a modification).

Adding a few more things to check:
Vacuum leaks / false air - Is the MAF boot tight? Vacuum hoses OK?
How old is the fuel filter,,, does it need changing?
Was the MAF gutted without an increase in fuel pressure?
Check your TPS voltage – idle should be around .5 volts, wide open throttle should be set as high as you can get it to go while retaining .5 volts at idle – wide open throttle needs to be at least 4.5 volts – less could give you a tip in problem.
Have the injectors ever been cleaned? Might need it if none of the above is the problem.

 

The car has had the injectors cleaned. New plugs, wires, cap+rotor, msd coil. air, oil, gas filters.

I added one of those electronic plug ins for the tps sensor but that didn't help.

I'll check the charging and the ground plus, I'll have the tps voltage checked.

I got the car a month ago. It had the problem all along. I though the tune up would solve it.

Regards,
G

 

my car has dones this since day one when i got it and it was bone stock. off idle response is very poor. but if i rev it from 1500rpm or so it revs real good. the car did this when it was still stock and still does it now, so does my buddies car. i noticed that if i have a timing light on the car, when i initially crack the throttle, i loose a few degrees of timing advance. the car has done this since day one and i figured thats just how it was. can anyone clear this up??

 

It could be possible header/cat/exhaust leak. I know that when my headers are leaking (dang gaskets) that my car gets sluggish of the line.

 

i dont know about anyone else's car but mine does the same thing and i dont have any exhaust leaks anywhere.

i encourage someone else to take a timing light on their car and see if they loose a few degrees right at tip in like mine does. with a timing light on and the set timing connector PLUGGED in, the first second that i crack the throttle i loose a few degrees, but they come back almost immediately and then the engine revs fine. so i suppose it is possible that i have a vaccum leak somewhere but i have rebuilt the engine, and swapped aluminum heads on, and had the intake plenum and runners off like 5 times, so i doubt that i have any leaks. what are some educated guesses here? this is like the problem on cold startup that many of us have, we probably all have the same problem but no one can figure out.

 

mine had that same problem, i got a new FPR and it is fine now....don't know if you are having the same problem though....maybe try unplugging the FPR vacuum source off the plenum and capping it on the plenum so you do not have a vacuum leak...?

 

What is the FPR?

 

fuel pressure regulator.