So I've got an 88 Iroc-Z, and its been a project and a half for the past 5 years.

It started life as a 305 TBI, when I bought it, it had an L98 long block installed, with the TBI system. I upgraded it to TPI using a modified TBI harness and BobR's Dynamic EFI system. When this was done, I pulled the motor and built everything, forged internals, ported 113 heads with stiffer springs, and a Crower cam, specifically for fuel injected applications, but mild enough for a stock TPI, 204 duration @ 0.050 lift, .484int .505 exh.. The car ran fine until the fuel pump went, and it all went downhill.

The car was behaving as though it had vapor lock; when the car was hot it stumbled, stalled, and refused to run at low idle. When cold, it ran fine.

Around this time my computer failed, and I could no longer use the Dynamic EFI EBL Flash to diagnose my car. After much chin-scratching, I checked the impedence of the stock fuel injectors, found two bad ones with low resistance, and replaced them with 30# FIC injectors and an AFPR. The car does the same as it did before, acting as though it has vapor lock. I do not have a fuel pressure gauge to check it, but I believe the car is running too rich and is dying out when it comes off Closed Loop mode.

I know I should re-tune the PROM to better fit my setup, but the car ran fine before, why has it stopped?

In order to use the EBL Flash to tune it, I need to get the car on Open Loop mode, which means I need to get the fuel pressure set right.

I know this seems like a rookie question, but tightening the screw on the regulator with the vacuum line disconnected INCREASES fuel pressure, right? Currently I have the AFPR almost all the way out (Loosened) and it still barely runs when warm. Turning it in seems to make it worse.

Any other suggestions as to how to solve my setup?

 

not an expert but sounds to me the injectors are to big for the tune you had with factory injectors. factory injectors are only 22lb and u installed 30lb. i would think the fuel pressure should be fine around 43psi. i could be wrong but if so someone please correct me

 

I know the injectors are big, I was planning for down the road if I do something a bit more wild. For now, can I tune back the fuel pressure to accomodate the larger injectors?

I also know I need to re-tune the PROM, but I need to get the car to run warm before I can do that. Currently it has a modified tune that was supplied with the EBL Flash.

 

those injectors are way too big. I've seen people with wild 383's using those and almost having too much. i would think if you can go down to around 30 psi it might balance it out don't quote me on that. trust me get a fuel injection pressure tester. I went to schmucks and they had one hanging on the wall behind the counter for 44.95 and it came with the necessary GM fitting already attached and ready to go. just connected the bleed line, put it in a gas can, and attached to the schrader valve on the fuel rail. made adjusting the afpr easy as hell

 

The reason I went with 30#'s is in case I go forced induction down the road; I didn't want to buy two sets of fuel injectors.

Schmucks? Is that a local place or a nickname for a chain? Either way, I think Summit has one, I'll have to pick one up.

 

Autozone has a nice one for about $30 bucks.

 

I rented a fuel pressure gauge from Autozone, hooked it up and set the pressure to 45psi. An experienced friend of mine told me not to back down on the pressure, as it will cause an uneven spray pattern (makes sense, less pressure). So I calculated the BPC table with my 350, 45psi and 30# injectors, and plugged it in my PROM. Works better!

At times, when warm, the engine still won't maintain constant idle (goes between 650-950). Also, the knock sensor goes up when it warms up, so I retarded the initial timing on the distributor to 4* after unplugging distributor wire. Knock went way down (from being almost maxed out above 1045 cnt to around 167) then went back up again to 260 as it heated up. Is this normal? Should I correct the Spark Advance some more? I definitely don't want to cause any engine damage....

Since I have adjusted everything, I haven't driven the car on the road, so I don't know if it is truly fixed or not, but it seems to be alot better.

Thanks again guys!