need some help please.
1990 iroc 305 tpi

bought it not running from sitting.

replaced
fuel tank
pump
sender
filter
injectors
temp sensor

i clean the fuel rail
but did not change FPR

car runs perfect on idle but under load as in driving it sputters and misfires

i started with plugs and it ran perfect for 2 miles and like someone flipped a switch it went back to the sputtering/misfire symptom

i then changed the
ignition module
coil
cap
voltage regulator

ran great for 2 miles and again went back to sputtering sympton

only thing that i can think of is the wires. the only part i have not replaced

idles perfect revs perfect in park
only when in drive and accelerating sputtering occurs.
#no codes#

maybe oil pressure switch?

how can it run perfect for a couple miles then all of sudden back to the sputtering.


any ideas?????

 

did you check fuel pressure?? maybe you got a faulty pump

 

new pump ac delco

 

Check fuel pressure, get a datalog.

 

was the car fully warmed up before the drive or warmed up on the drive ?

 

car was warmed i drove it for a couple miles absolutely perfect night b4. i got on this am stated warmed for 2 min drove off 1/4 mile down like someone flipped a switch back to sputtering misfire no power.

 

It almost sounds like icm but since recently replaced I wonder about pu coil condition.

 

Makes it sound like an open —> closed loop problem.

Most usual cause of those, is the coolant temp sensor. In open loop the ECM runs off of a pre-programmed program; in closed loop it starts looking at all the actual inputs it's getting from all the sensors. Main cue for it to do that, is coolant temp. Check that in your data log. Or, if you lack the wherewithal for that, just swap out the CTS. Less than $20, probably 15 minutes if you're slow like me, you can probably do it faster like most everybody else.

 

that was the first sensor i changed. would oil pressure sensor near filter do the same ? i read a post where it was.

 

The ops is backup for fp relay. So unless you’re pump isn’t running i wouldn’t replace it.

 

I've done some diagnostics. My fuel injectors test at 13.3 ohms warm, and fuel pressure is initially at 40psi to 30 but drops quickly there after. I've ruled out some potential causes and think it's an injector leak. When I installed the fuel gauge and removed the MAP sensor/brkt, the car ran smoothly hold fuel pressure 35-40 However, with the MAP sensor reinstalled, it ran rough. i went through this twice same result.
i remount the map at an angle it it runs great short of a slight rumble in acceleration most likely from the injector leak

any thoughts on maps and the mounting
should i test it or just replace

curious why car runs great with the map moved off the manifold to the side???

 

What injectors were used to replace the originals ? . As long as the map has a good vacuum connection it could be mounted any position and still work. Sounds like there is something wrong with it.

 

Misread your post, removing the map completely changes its reading. More than likely leaning out the air fuel ratio.

 

i didn’t remove and disconnect i unscrewed the brkt only for access to the fuel rail valve.
vacuum line and plug still connected just laided over to the side

 

Maybe have your mechanic look at it.

 

burd

idiot!

 

as you can see he’s asking for advice to fix himself