russelld

Just got a 94 z28..ides fine and revs fine in park..misses like crazy when u try to drive it..10 mph is about all I can get. Has afr heads lt4 hot cam lt4 intake holley throttle body jet chip headders and supposedly lt4 bottom end. Fuel pressure is normal fuel volume is fine I replaced both 02s ,spark plugs,checked all the grounds replaced the coil, checked compression and no change. Also it supposedly has ford injectors they are black and red . I'm thinkn the opti is junk..someone help I'm a gm tech and this car is kicking my butt

Injuneer

Has it ever run right? Has the PCM been tuned for the heads and cam? Stock injectors or larger ones? The JET "chip" is probably the unit that inserts between PCM and the harness connectors. Can't tune with that. 94 and up has a fixed chip, and requires flash programming.

Nothing wrong with the Ford injectors (SVO, FMS, etc.) as long as they match the flow constant in the tune, and offsets have been programmed.

Have you scanned it for codes? Problems with the Opti's optical cam position sensor will set codes (DTC 16, DTC 36. 16 does not turn on the SES light). Problems with the high voltage side do not set codes. Have you tested the ICM.

What were the results (psi) when you tested the fuel pressure with and without the vacuum compensation line connected to the FPR. Did you test the pressure with the engine under load?

Have you checked for a plugged cat (if you still have one)?

russelld

When I first got it it would stumble at low end then clear up.guy said it had been programmed but not sure..data stream on the tech 2 sems normal. Nothing really jumps out at me..had a lean bk 1 code bt the o2 was bad..need to check again though but no opti codes. Gonna get the icm tested today. And yes it's the jet module between the pcm connector..just found tht surprise and I'll chk cats tonight. Good idea..crazy tht it would clear up and now it's awful and wont. This car is driving me crazy thinkn about this..I appreciate your help man

russelld

Has adjustable fuel press reg too ..low or high pressure doesn't change it

Injuneer

Set the fuel pressure where it belongs, and then leave the AFPR alone. 43.5 psi with the vacuum line off. When you raise or lower the fuel pressure, the O2 sensors report the change in A/F ratio, and the PCM adjusts the long term fuel corrections to compensate.

Is there any sign of wet fuel in the vacuum compensation line?

When testing the ICM, make sure it gets good and hot.... heat soak can cause problems.

russelld

I did its at 43.5 guy had it at 60 I thought for sure tht was my problem but no dice..I'll go after work and test the icm and update here..fingers crossed. We just got a ta same year and about same mods here at the dealer I work for so I'm gonna look at the data and compare it to mine

Injuneer

Maybe he raised the pressure to, in effect, increase the flow capacity of the injectors. But when that is done, the program has to be changed with the new flow rate.

Run a data log with Scan9495 - free download here:

https://www.camaroz28.com/forums/com...95-lt1-874306/

I've been reviewing LT1 data logs for more than 15 years, and can help.

russelld

I have a gm tech 2 what data parameters do u want to see

russelld

Had the icm tested..advance said it's bad auto zone said it's good ....my kinda luck lol

Injuneer

Did they test it repeatedly to get it good and hot? I have a list of parameters that I give to people who have TTS Datamaster, so they can setup the .csv format data log export. I'll post it when I'm on my PC and can copy and paste it.