Last summer i bought my self a Corvette 1990. (L98 350 TPI, 6-shifted manual transmission)
The car seems pretty much original except the exhaust pipes.
As long as i've owned the car it's been bugg'n me

My problem is pretty much the following:
* Sluggish at low RPM's and at idle.
* Even more sluggish when entering closed loop.
* Sometimes it backfires when shifting during inspired driving.
(This also happens sometimes when i quickly rew the engine in "neutral")


Stuff that's been tested and has been changed.
* Ignitionwires & spark plugs (Checked behavour in darkness)
* New Lambda/O2 sensor
* Ignition module
* New fuel filter
* fuel pressure
* New Fuel pressure regulator
* Vacuum-hoses conserning MAP & fuel pressure regulator
* Tested Compression at all cylinders.
* Distributor has been checked a bunch of times.
* Checked for intake leaks.
* Original Chip
* No error codes
* EGR-solenoid checked
* Tested with other ECM
* New EGR-valve
* New MAT-sensor
* New MAP-sensor
* Checked resistanse of injektors

At idle my BLM says: 108
Maximum reducement of fuel.

Yesterday i checked the OFF-fuel pressure again.
Started at 41 psi but within 5 minutes it went down to 0.
Is that normal behaviour?


All hint's are welcome!

 

Sounds to me like one or moere of your injectors may be leaking. That's probably why your fuel system won't remain pressurized longer than five minutes. It's also likely that it's causing your excessive fuel-reduction correction by the ECM.

Since you only have one O2 sensor, start with the injectors on that side of the engine. Either have them tested or rerplaced- the latter being your best bet since it's a pain the in the you-know-what to take that TPI apart again.

 

Thank's for answering!
I belive it's time to get my new Ford SVO #24's in place now.

 

if you put the SVOs in, either get a new PROM burned or lower your fuel pressure a few pounds. Those SVOs are quite a big bigger than stock and without making proper adjustments can cause the car to slow down.

 

I'am aware of that.
I will try to solve this issue by stating a higher injector flow constant in the prom.

 

I'm running with 24# SVO injectors. My injector constant is 27.2 and I'm using 50psi at the regulator. That'll give you an idea of where to set your constant.

 

Thank's again guys!

I'am going to use original fuel pressure and start with
25 for injector constant and increase from there.

 

That's exactly how I've got mine set up and my block learn value never drifts past 126.

 

What value did you end up with?