Harder to start after injector and O2 replacement

[Cam2363]

96 z26 3.1L

I replaced my injectors and O2 sensor today in the quest of better MPG, and after, the first start was rough, but I expected this, what I didnt expect is the start about 4 hours later to struggle. Before this, you would turn the key for under a second and it would fire right up, but now it cranks longer and kind of sputters to life, like it doesnt fire up smoothly, so I drove it, got it warmed up, and it did the same thing warm, took a while to crank, didnt go instantly as it used to, try again for a little longer, sputters to life. But once it is running, it runs fine.

Does anybody have any ideas on what to check? I have no lights indicating anything.


UPDATE:
I did a fuel pressure test, it goes up to around 41 or 42 psi, which according to my manual is normal, but after a few minutes drops down to the low 20s. I starter the engine and it goes down to around 37 which according to the manual is also normal (3-10 psi drop when running). I also checked around the injectors and around the inlet and outlet pipes and there is no fuel around them. So my guess is that some injector is leaking into the engine. Anybody know how to figure this out without taking everything apart? I check the front plugs and they look fine, the back ones are too much of a pain to remove tho lol.

And I have checked the connections on the tester. There is no fuel leaking, nor can I hear any air leaking out of them.

And I used my remote start to start it cold the other day, and it took probably around 4 to 5 seconds before it started and ran.

https://imgur.com/a/1c8HYnc

Thats a link to a video I took of it starting using my remote start

[Bapsu]

U sure ur injectors are good? Sounds like some of ur injectors is leaking which makes engine hard to start..

[Cam2363]

U sure ur injectors are good? Sounds like some of ur injectors is leaking which makes engine hard to start..

How would I diagnose the leaking injectors? I mean they were all brand new injectors

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[Rettax3]

Buy or borrow a fuel pressure test-gauge (most auto-parts stores have them in their loan-a-tool program, so you are out your deposit for a short time but use of the gauge is basically free), turn the key on and off a few times to purge any air out of the lines and check the fuel pressure. With key off, watch the fuel pressure. If it keeps bleeding down, you have a problem, and while the problem COULD BE the anti flow-back valve inside your fuel pump or it COULD BE the FPR leaking, since you didn't have these symptoms before the injector swap would be fair to guess a leaking injector. Where did you get them from?? New doesn't always mean good... I would also say that you could try swapping the O2 sensor back in to pin-down which side the problem is actually in too, but just guessing I would say Bapsu probably has it right. If you do have a leaky injector, a mechanic's stethoscope might reveal which one it is, depending on how bad the leak is. You could also pull plugs and find out which one smells like gas.

[Cam2363]

Buy or borrow a fuel pressure test-gauge (most auto-parts stores have them in their loan-a-tool program, so you are out your deposit for a short time but use of the gauge is basically free), turn the key on and off a few times to purge any air out of the lines and check the fuel pressure. With key off, watch the fuel pressure. If it keeps bleeding down, you have a problem, and while the problem COULD BE the anti flow-back valve inside your fuel pump or it COULD BE the FPR leaking, since you didn't have these symptoms before the injector swap would be fair to guess a leaking injector. Where did you get them from?? New doesn't always mean good... I would also say that you could try swapping the O2 sensor back in to pin-down which side the problem is actually in too, but just guessing I would say Bapsu probably has it right. If you do have a leaky injector, a mechanic's stethoscope might reveal which one it is, depending on how bad the leak is. You could also pull plugs and find out which one smells like gas.

Already did that test as seen in my update. I'll try to get those rear plugs out today and see if any of those smell of fuel. I bought them off of ebay https://www.ebay.com/itm/Fuel-Injector- ... 1008309579

I do have another used FPR I can try swapping in and see if that makes a difference

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[ifixalot]

My two cents. Ox sensor comes into play after engine warms up so, cold slow start cannot be attributed to that.
Since injectors were changed and the then problem started, the injectors or something you did changing them is suspect.
You could try and put some gas in the throttle body. If it fires right away you know it is starving for fuel, if not, it may be too much
fuel. Yes, read your plugs and see if they are wet and thus running rich.
I doubt fpr, why would it suddenly go bad?

[Cam2363]

My two cents. Ox sensor comes into play after engine warms up so, cold slow start cannot be attributed to that.
Since injectors were changed and the then problem started, the injectors or something you did changing them is suspect.
You could try and put some gas in the throttle body. If it fires right away you know it is starving for fuel, if not, it may be too much
fuel. Yes, read your plugs and see if they are wet and thus running rich.
I doubt fpr, why would it suddenly go bad?

I wasn't thinking o2 for the same reason. And same for the fpr I'll have to try that later then

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