Hello folks long post. My 92 LT1 stumbles under heavy acceleration. Intermittently.
Whole story.
I bought the car from a mechanic for $150+ a diamond wrist watch.
It wouldnt start.
The fuel pump and sending unit was rusty.
I cleaned out the fuel tank by hand. And replaced the pump and sending unit. Still no start.
I replaced the fuel filter and regulator. It would start but shut off after a second or two.
I took the injectors out and DIY you tube style cleaned them. The car finally ran but bad under heavy acceleration (Sometimes).
I then replaced the spark plugs, coil and opti spark (autozone duralast lifetime warranty) runs ok not good while cold but gets worst after warming up.
I checked these sensors while running.
Idle air temp sensor. No difference
trottle position sensor. idle raised
ignotion control module. Shuts off
optispark connection under fuel rail. Shuts off
egr connection. No difference
coolant temp sensor. Fan turns on
Each injector connector. Stumples at idle after I disconnected each one by one.
I don’t have a fuel pressure gauge

 

Get one, you can't troubleshoot without it. It has already cost you a pump and sending unit because you couldn't eliminate this being your issue. How do you know you have enough fuel pressure to run... you are going to need to know idle pressure and pressure at RPM. Lack of fuel can cause stumbling.

That doesn't mean a lot. You still don't know if one has a problem.
You are going to need one to do a leak down test and then you need to do a resistance test to know they are good. If you are comfortable they are clean you can eliminate that issue but it doesn't mean they function properly. Even if it isn't the issue today, it may be an issue soon. Seems the TPI cars started to have a lot of issues in the 25-30 year range. You car is about to hit that window.

Probably your issue, do some reading around here. The Duralast usually fails frequently. The warranty is good for getting free parts, but it doesn't keep you from breaking down or having to do the replacement. I suggest you send your old stock unit out for rebuild. Read around and decide on your source. Though, before you go through all the labor to swap it out again, please do some troubleshooting. It may not be your issue, but I would still get your old one rebuilt to keep as a spare. The Duralast seems to have a 90% chance of failing based off what others have posted.

All good stuff... any codes?

Have you reset your computer yet (Pull the negative battery cable for about 10 seconds)

 

By the way, you can get a fuel pressure test kit with gage at most auto parts stores that have a loan a tool program.

 

Thanks for the reply. I was getting a code 16 if i step on the trottle hard over and over.

 

Dtc 16 relates to Opti spark low resolution, to DIY you need factory manuals. Corrosion is a concern with cars that sit. Make sure ground connections are clean and tight with no corrosion. Make sure female terminals aren't spread from probing causing intermittent condition..A test terminal or something about .040 diameter should work.

 

My car exhibited the same symptom (missing under heavy load when hot) when the opti started to take a dump. You need to determine if it is really the opti causing the miss. Do you need a scan tool or FSM to do that? No you don't. When the symptom occurs, does the tach needle jump/bounce around? The "now, now, now, now, now..." originates at the opti (like points, in the old days). If that is causing issues, then it should show up as erratic tach behavior when the symptom is happening.

 

Ok I have a fuel teater and the pressure is at 30psi while idling under heavy acceleration it drops to 10psi.

 

fuel pressure to low, replace fuel filter and retest and go from there.

 

Yep, start with the easy stuff because with a new pump, you should have a new filter anyway.
You should also test voltage at the pump, make sure it is not a wiring issue.

This doesn't rule out you having an unhealthy Opti, but that fuel pressure is definitely low. While it may be your regulator, less pressure at higher RPMs is usually a volume problem from the pump. Replacing the regulator would also not be a bad idea given the age of the cars, it's pretty accessible and cheaper than a pump. While I am not a fan of throwing parts at a problem, changing the regulator and filter with a new pump is cheap/easy to prevent future problems.

 

Id trust that unit about as much as marrying a STRIPPER which translates to ZERO
I’ve stuck with OEM AC Delco on any of my F-bodies and C4’s and never had an issue...