chaseincats

Interesting idea and good point with the 39 psi

Update: the car is running great now. Here is what I did and found: New plugs did not help (car lean running issue continued after installing these) Pulled new plugs from the head and watched them spark - spark level was identical Measured HT wire resistance - all within spec Went through the fuel injection bible and confirmed all components are within factory spec when measured through the main ECU connector Fuel pressure at 32 not 36 changed engine bay fuel filter but did not re-measure fuel pressure Pulled the fuel rail, put all 6 injectors in separate cups and measured the fuel output volume while cranking All injectors output identical volume with identical spray pattern (injectors are ~1.5 years old) Cleaned injector connector teeth - cylinder 1's injector teeth were green but this did not affect injected volume I did notice a couple small black pieces in the injector inlet size so it may have been the fuel filter which was odd since it was only about 2 years old. I will change the tank to fuel pump filter this week although it looks clean

interesting and a really good point. I'll pop the wires back in then

It doesn’t, but plug wire resistance was my friends theory yesterday when I showed him cyl 3 was darker than the rest.

A friend last night suggested checking the resistance of my NGK spark plug wires (bought in 2021). I set my multimeter to 20k ohm and here is what I got: - plug wire cylinder 1: 6.40 - plug wire cylinder 2: 6.03 - plug wire cylinder 3: 6.03 - plug wire cylinder 4: 6.68 - plug wire cylinder 5: 7.07 - plug wire cylinder 6: 7.2 Is any of this suspicious?

I remember testing it a while back and it was on the low end of normal on atlantic z meaning it had ~17 lb at idle at 800 rpm - "An engine in good condition should have a gauge reading of 17 to 21 and hand should be steady". When the car is running and I pull the FPR vacuum hose, it sits at 39 psi. Coincidentally I tested the injectors by pulling the fuel rail, sticking all of the injectors in cups and cranking it over the weekend - the spray patterns and volume were identical which was great news. I did just change the fuel filter today so we will see if that does anything but it was only a few years old and there already is a clear filter between the tank and fuel pump.

Gotcha, that makes sense. So mine reading ~32 is fine then? At what psi would you say is a red flag for low fuel pressure?

I'm confused, doesn't the fsm say the idling fuel pressure should be 36?

completely unrelated efi question: do all the injectors fire at the same time or do they fire individually in time with each cylinder?

That's actually where I tested the temp sensor from, but good recommendation

Yep - at this point I'm kind of at a loss. Checked plugs, checked temp sensor, checked all electrical connectors at the ecu, checked injectors - so we'll see if any of these 3 are the ticket.

Hi gang, So I pulled my injectors, put them all in individual cups and cranked the engine for a bit and all seem to have the exact same level and spray pattern (see video here). I did however notice cylinder 1's injector connector teeth had a pretty solid amount of green corrosion on it which is weird considering these are only a year or so old with brand new harness connectors. I did also notice small black particles in the gas coming out of the injectors - I'm not sure if that is just dirt from them resting on the head while waiting to be put in the cups or not. Long story short here is where we are: I filled up the injector's plug area with caig de-oxit and let it sit all night and ill remove the corrosion this morning I will get a new engine bay fuel filter just in case it's not just dirt sitting on the engine intake plenum while they were resting there Switch injector #3 with a different one to see if the darker plug on cylinder #3 darkens darkens on the cylinder with the moved injector or not

Good call on watching the tach needle. It is a fuel problem, as the needle behaves itself haha. I will pull the injectors in the coming week and see if they are all firing at the same rate.

Interesting - It did run really well yesterday but granted I didn't drive it, just idled it until it got to temperature so I could get readings with the fuel pressure gauge. so maybe not?

I don't remember which make/model it is, but there is one of those clear plastic filters between the tank and pump. I checked it yesterday and looked fine.

I believe its a few years old

Good to know this exists. This was a problem that just cropped up while driving so it has to be something mechanical rather than aging ecu related I'd think.

It was definitely running worse than it had in the past, and the rough hot-start idle was new. That said, it was running great today and didn't even have the hot start issue so I'm not sure what's going on. I will take the rental gauge I have to my friend's place tomorrow and test it on his z to see if it reads 36 at idle or if it says 32 which would mean the gauge is just off.

I haven't since its just a hose gauge from oreilly's but I did start the car this time and let it run to temperature and watched the gauge as the car warmed up and at a variety of different rpms. The car never went above 32 when idling at any heat range if that helps.

Update: the gauge is saying 32psi idling. When I tap the gas and hold it, it will go up to 38 but drop back down to 32. Isn't idle PSI supposed to be 36? If I unplug the vacuum line to the pressure regulator it will sit at 40psi when idling. Gas is not coming out of the pressure regulator with the hose unplugged.

@Zed Head Fuel pressure looks good - 38 at cranking.

coincidentally I just got off the phone with oreillys to confirm they had a fuel pressure test kit - will get back to you with an answer on that tonight

It's weird this would just start all of a sudden though. The car started running really lean on the freeway out of the blue, I had to get off the freeway and richen it a tooth on the AFM because I was concerned about potential engine damage if I didn't (it read 18 on my AirFuel gauge all of a sudden and started to misfire). Cylinder 3's spark plug looked very rich compared to the others.

Hi guys, I'm running lean all of a sudden and not sure why. It is worst when hot-starting with a very lumpy idle that stabilizes after a minute or so but it is weak throughout the rev range (unless flooring the pedal). The idle stabilizes the longer it sits but is definitely misfiring (or not firing) when hot started. The idle is very lumpy but also smells very rich. New plugs with ~2 hours run time on them. Injectors about 2 years old. Any idea on the below plug images?

Looks like we have something mechanical/unrelated causing all of this - I'll make a separate thread EDIT: As a heads up for those reading this thread to tune your cars, the problem ended up being unrelated to the tuning and was instead an issue with cylinder 1's injector connector. The thread where this was solved is titled "Sudden Running Lean Issue" if this happens to you.