Hey Everyone, Ended up killing my 305 for the first time. Original motor at 176K and my 3rd 700r4. I had just finished up a Restomod on a 73 Z28 I gifted my mother so I decided to swap in the FMVB 2200 stall th350 into my 91 bird for now. Engine never really had oil pressure but also never let me down but obvious oil starvation showed. In favor I put in a 355 I've planned to swap in forever ago specs as follows.
Lt1 24lb Injectors
Stock fuel system
LT4 Hot cam kit
SLP runners
Ported 9th injector plenum and base.
Headers w/ Heated o2
113 heads
AC/EGR/auto trans deleted in tune

Im having an idle issue, initially 600-1100 rpm fluctuations and finally dying in my driveway after a long drive, pedaling the car to keep it running. replacement of IAc and shotty connector resulted in a less RPM fluctuation at steady Idle 600-700ish. I've verified sensors manually, Vacuum is good with no leaks via gauge, and good old ether. Fuel pressure consistent.

I have a lot of people telling me to get a AFPR and retune, I feel its unnecessary with such a mild build, some say fuel injectors could be bad. how do I truly verify, it was my understanding for batch fire if one goes so does the whole bank? The 9th injector intake setup and runners was given to me. I did notice the bores on the side of the plenum for the runners we notched just as the gasket and runners are. but oddly there is a notch on the gasket and plenum for the throttle body. could this ultimately be my issue? Anyone have other ideas here? I am down to verify things, im not keen on just replacing them to replace them. My tests have concluded the majority of sensors and such are active and functioning properly. Car is in for winter storage and there's a few other things to take care of but ill try to see if my old Snap-On brick scanner can read anything off it as well. I don't suspect much since when using Tunerpro and datalogging didn't give me any false sensor readings.

 

You should get an AFPR and retune. Do you know for sure that you have the right year throttle body for that year of plenum? Also, there's two different throttle body gaskets so you need the right one of those for your application as well.

 

not sure what gasket i have. its my stock plenum and tb. and runners and lower have the 9th injector stuff blocked off. whats the difference between gaskets?

 

https://www.summitracing.com/parts/fel-ms930351

In the full fel-pro intake gasket kit there's 2 different kinds. My '89 had open center style on the right I think, and that's what I replaced it with which seems to have been the right choice. The smaller kits only come with the left one, not sure what years they're for or whether that would be causing your problem.

 

Yep so i verified gaskets, plenum, TB etc all match. the lt1 injectors ohm out to 12.9 both hot and cold. if this correct or should they be higher? im getting conflicting info.

 

Matters not whether resistance is higher or lower cold or hot and 12.9 is OK. Just want to make sure resistance is approx the same for all injectors at temp X. That's why a hot check is good because temp may affect a coil. All an ohm test is telling you is that the injector coil is OK. it does NOT tell whether they are working properly. Have had injectors ohm perfectly but caused problems. Generally, idle/low RPM issues are due to improperly operating or leaking injectors. Can also have off idle tip in issues where transition is not smooth under mild acceleration resulting in periodic hesitation. And if they are original factory injectors, that's likely your issue.

Might try logging the idle problem with TPro once in Closed Loop. Then export the log in TPro to a .CSV file and post. That will provide some insight as to INT, BLM, PW, etc.

 

Ill have to figure out if i can borrow data log cable again. mine has gone missing. I tuned my car with my buddys Moates stuff not my own sadly. I checked temp with vehicle at operating and they were still at 12.8/12.9 through all 8. how do i determine its working properly? Snapon scanner might give me BLM and such as a readout.Have put alot of focus on my truck and not really messed with this at all.

 

A log is needed to see what BLMs are at all engine states. Otherwise, impossible to determine.

 

Well that sucks, guess im not gonna get anywhere since I dont have any of that equipment anymore. EDIT: buddy found my cable in the truck i sold him lol. time to revisist how to find my bin/xdf/adx files and get a log going

 

Is it fine when you first start it then gets worse the longer you drive?


I had similar problems..... funky idle, stalling.....turned out to be he car would fluctuate because it was fuel starvation. it was getting fuel but not enough I guess volume so the ecm did all kind if things to compensate like raise the idle. oddly it was the vent valve was stuck shut and created a vacuum that wouldn't let the pump send enough fuel to the motor, or the fuel to get out of the injectors.... .... it had pressure but maybe not enough volume or the vacuum was preventing the fuel from leaving the rail...kinda like how you cover the top of a straw and the soda stays in the straw....or some other kinds of physics I don't understand lol Sometimes it would get SO bad the car would die and I would have to get out and release the vacuum pressure in the tank so I could start it again. The woosh of air was massive....


Might not be it but worth a shot? Easy test that requires no tools.....Just release the gas cap and see if it helps when it starts acting weird / stalling.