I have always gotten really bad mileage on my Vette. 12.5-13.5 mpg is my average across almost two months of driving to and from school/groceries/the gym. Car stinks of gas and it doesn’t pass smog. Other than that it was running fine up until a couple weeks ago, the car stalled out on me when I tried to go home after class and I couldn’t get it to stay running without revving the engine for almost a minute or two. The few days prior I had noticed it was running worse and I tested the fuel pressure. An abysmal 28psi when primed, and dropped to 22psi after 45 minutes.
Here’s what I have done:
1. Ohm injectors: all good and within .1ohm (except cold start, which was expectedly at 3.8ohm)
2. Pull spark plugs: slight carbon fouling on every plug, all of them were “wet” with what I hope is gas. Photo below.
3. Replace fuel filter: previous filter wasn’t terrible, could still blow through with resistance. New is always better though.
4. New O2 sensor 6 months ago.
5. Previous owner messed heavily with emissions components: EGR solenoid deleted. EGR vacuum hose bypassed. AIR pump hoses disconnected. Diverted solenoid deleted. Canister still present and connected as far as I can tell.
6. Seafoamed the engine and oil about a month ago
7. Have new fuel pump, pump sock, FPR, plugs, and O2 sensor on standby

After the fuel filter replacement, fuel pressure is up to 44psi at idle but dropped to 36 after 10 minutes and 34 after 15min. This indicates to me that either fuel injectors or the FPR is leaking. Injectors are unbelievably expensive, and I can’t find any of the ford 22# ones for sale that have been recommended by others here. Also, the car throws a code 13 intermittently however the O2 sensor is working, I believe the exhaust is just so rich that the ECM believes there’s an issue. Per tunerpro, BLM stays at 108 and O2 reading is above .9 most of the time. When the Code 13 is thrown, the engine does not leave open loop.

Is there something I am missing here? Does anyone have fuel injector recommendations for an ‘86 for sale right now?

 

Check with FIC for fuel injectors, the plugs look to be oil fouled to me. Try replacing the injectors with the correct parts and then see if it is burning oil.

 

"7. Have new fuel pump, pump sock, FPR, plugs, and O2 sensor on standby"

Does this mean that you have an O2 sensor on standby or all of those parts are on standby? I didn't see you otherwise mention the FPR.
Reason I ask is that often (not always) the FPR diaphragm has a leak and lets fuel pass through the vacuum line and make the mixture rich.

sre

 

I had all of those on standby. Yesterday I replaced the fuel pump, sock, and fuel pressure diaphragm. I also found out one of the PO installed an adjustable FPR, so I reduced the fuel pressure to roughly 38psi. I've only taken it on one drive so far, but according to tunerpro RT, I'm switching between lean and rich more consistently, rather than spending 95% of the time in "Rich." However, I now lose all fuel pressure within 10 seconds of shutting the car off. Clamping lines didn't affect the rate of loss either, but to be fair I'm not 1000% sure I did that test right. I read somewhere than AFPRs are intended to do this, but I can't find that thread again.


Doesn't look like FIC has any of the 22lb injectors that the C4 uses. I'll email them to check. If I replace the injectors and I am burning oil, am I going to end up frying the new injectors?

Edit: I think I found them: https://fuelinjectorconnection.com/p...sch-design-iii

And I just remembered, yesterday when running the engine, I put my finger on top of each injector and could feel every single one ticking rhythmically. I'm just now connecting the dots that they're probably struggling/dying/dead right?

 

No, injectors will tick and make a small amount of noise normally.
An adjustable fpr doesn't "leak down".
When you sat you lose fuel pressure, is that with the car running, or when it's turned off?
I just replaced my injectors, I bought Bosch 3 from South Bay Injectorson ebay for $210 delivered.

 

the car maintains fuel pressure totally fine when running. Once switched off it loses pressure immediately also if i prime the system, sometimes fuel pressure will haves dropped before I even have the chance to hit the ignition. As long as the pump is running, pressure is held fine.

 

The fuel pressure drop may not be a big issue, depends why it is dropping. Fuel is non-compressible so even a small leak past the regulator to the tank or a leak from the pump back to the tank will cause a quick drop in pressure. My car has done this for 20 years and it runs fine (A non -issue) What you don't want is a leak from the injectors into the intake manifold causing the fuel pressure drop or a leak from the regulator vacuum diaphram to intake manifold, if that is not happening you are OK. Burning oil will not wreck the new injectors. Don't just replace parts, verify that you have a problem with the injectors before you spend money on them. Have you verified that they are the factory injectors with the factory rating?

 

That was my thinking as well, and why I was only replacing service items up until now. I would have to pull the fuel rail to inspect the injectors right? I’ll do that this weekend. Assuming it isn’t the injectors, could I add a bypass switch to the fuel pump so I can maintain fuel pressure when trying to start?

 

No need to add a switch, as soon as you crank the car the fuel pump will turn on.