running rough!!

[Rootie524]

also i saw in another thread about twisting the crank position sensor wire..is that for the 24x or the 3x sensor? because i got the 24x replaced and didnt twist anything..it was in a wire insulator sorta thing and didnt say to twist..so it must be something else but im just thinking of possibilities.

[Rootie524]

I'm about to drive my car off a cliff.

Today i was driving around with my computer..and the PCM FINALLY gave me something i can use. It started throwing me cyl 4 misfire. So that narrowed it down a lot...or so i thought. So i went to autozone..got a new coil pack for 1 and 4. Put it on..got a little better and still bad. Then (since i had the junkyard ICM on) i put my original ICM under the coils back on. it got even better. so at this point im steamed..idk what else there is. I change the cyl 4 ignition wire..still not working. i change the spark plug..still not working.

Also..i probably shouldn't have done this..but at the exact same time i started working on it i put in some techron fuel system cleaner because the guy said it could be an injector (which was one of my first instincts to begin with) and he said there has been a few cases of water getting in gas and since water is heaver than gas that screws shit up.

So since i did that at the same time.. idk if my new spark components are helping or if the fuel injector cleaner is. it seems to have gotten better because when i drive it goes in and out of good running. like poor then good then poor than good...off and on soooo much. before it was bad for a long time, good for a short time. now its like a switch keeps being flicked off and on..its still worse more than it is good..but something is going on.

if i sit still in park and rev it up to 3 grand and hold it there...u can feel, hear, and see it cut back and forth between good running and poor running.

also..i have no idea if this is just coinicidence but when it was running bad i pulled over..opened the hood and pulled the hose off that goes into the top of the FPR..then went back in a revved it and it was good. Idk what that hose does..but i know its goes to the FPR..so when thats off..what does it do? iirc it makes the FPR run at max psi? so either i need a new FPR, new MAP sensor (although it gives a reading on the scantool), or my fuel injector(s) are indeed fucked.

I'm getting there..but im glad it's at least been narrowed down to a select few issues. still annoying as hell though.

[Rootie524]

ttt

sorry dont mean to be impatient but im about to work on it..seeing if i can get some input quick. fuel problem or still spark?

[pocket-rocket]

opened the hood and pulled the hose off that goes into the top of the FPR..then went back in a revved it and it was good. Idk what that hose does..but i know its goes to the FPR..so when thats off..what does it do? iirc it makes the FPR run at max psi?

Yes. If you had water in your gas I would expect that it would run like crap the most after sitting for a few hours giving the water and fuel time to separate. Vacuum (what the FPR runs off of) is from the engine creating a suction from pistons going down in the bores fighting against the throttle plate. When you hit the gas and the throttle plate opens, there is less vacuum because the "blockage" (throttle plate) is opening. Your vacuum reads 0 at WOT (unless your air cleaner is severely plugged) so at WOT, the FPR gives the injectors max fuel pressure. Have you thrown a fuel pressure gauge on it yet? My friend has an F150 that's been acting up and throwing a lean condition code so I tossed mine on there. His fuel pressure would actually go down when the throttle was goosed because the engine demand for fuel was more than he was getting to the rail. Normally as you goose it, fuel pressure rises (less vacuum).

[Azrael]

I'd say it's safe to move on to diagnosing the fuel system. It would help to see what your BLM (long term fuel trim) is like. Could be a lean or rich misfire if an injector isn't opening enough or leaking.

[Rootie524]

well it weird though.. it sat all night and when i started it today it was running great. i started driving and it was good with the occasional misfire..then it started getting worse and worse and worse. It started off ran good, then misfired very little off and on..the it was about 60/40..then 50/50..and 40/60 then 30/70..meaning the longer i drove it (probably a total of 30 minutes) the worse it got (stayed running bad moreso than running good) and i noticed if i put it in neutral while driving and revved it it would sometimes go away. and at higher RPMs it seems to go away. it comes back..but if u toy with it ever so slighty i can get it to go away for a short period of time.

it seems to be better than it was..but something is STILL up. and it STILL says cyl 4 misfire. it has a new plug, wire, and coil..is HAS to be a fuel problem!

it would make sense that it would run better at higher RPMs because the injector has to fire more..so maybe it gets clogged or stuck at low RPMs when it's hot. because when its cold it's alright. or maybe its not getting enough fuel for some reason and its burning up. but i would think if 4 isnt getting enough fuel, neither would cyl 6..

but ill check the pressure at the rail and see whats up. somebody should surely be able to give me a diagnosis based on the story i just explained. hopefully at least.

[Rootie524]

I'd say it's safe to move on to diagnosing the fuel system. It would help to see what your BLM (long term fuel trim) is like. Could be a lean or rich misfire if an injector isn't opening enough or leaking.

yeah ill check the rail pressure and ill plug in my computer and post of the fuel trims. i really need a wideband o2 right about now.

[86FieroSEv6]

Ya' know . . . . this sounds like junk in the fuel system. The "bad stuff" will fall away from the sock and settle in the tank, then when you are stirring it up and the suction from the pump inlet draws the crap up on the sock it'll starve. Now, that sounds all okay except for the issue of being one cylinder that is affected, and intermittently at that. Here's an experiment. Backprobe the #4 injector circuit at the plenum subharness connector with a computer safe test light. The good ones have a red and a green LED to indicate whether the circuit is grounded or hot. You can even use an extra long jumper and run it inside the car so you can monitor the #4 circuit while driving. What we're looking for is whether or not there is an injector driver failure.

[Rootie524]

You're gonna have to dumbify that up a bit for me..haha. i understand what needs to be done..but not exactly how.

i might just say f it and just replace the injectors and see what happens. only problem is the only injectors i have ATM are 19#ers..im guessing that wouldnt work in an application thats used to 22.5#..i'd lose power? or would it be fine because my dyno guy said im only using like 60-70% duty cycle on my current ones at WOT.

[robertisaar]

You're gonna have to dumbify that up a bit for me..haha. i understand what needs to be done..but not exactly how.

i might just say f it and just replace the injectors and see what happens. only problem is the only injectors i have ATM are 19#ers..im guessing that wouldnt work in an application thats used to 22.5#..i'd lose power? or would it be fine because my dyno guy said im only using like 60-70% duty cycle on my current ones at WOT.

are your current ones rated for 22.5 at 43.5PSI or 55PSI? because sticking in 19# 43.5PSI injectors in place of 22.5# 55PSI injectors will actually come out VERY close, assuming you drive them at 55PSI. the electrical connector would be different though.

[Rootie524]

well according to haynes the fuel pressure at the rail should be 52-59 PSI..so i'd say it is 55psi

there was a page either on here or on wot-tech that had certain years engines and what injector # and PSI corresponded to it..but i can't find it.

[SappySE107]

55psi and 22.5# is what they flow at for 2000 and newer 3100/3400 engines, but not what the computer is programmed at. Probably rated at a lower psi based on vacuum.

[pocket-rocket]

I was going to say, if you don't have another set of injectors, swap the one for #4 with another cylinder and see if the misfire code follows it before buying a new one.

[Rootie524]

well idk what the deal is. i drove it today..started it up.. ran rough..and did the thing where its good then its not. went to my friends house for a party..a few hours later came back to my car..started it up..ran great the whole way home..not even the slightest hint of a misfire.

did i just have a dirty injector and that fuel cleaner is working wonders.. im going to be pissed if i had to put all u guys through this stuff and myself through ripping shit apart and buying new crap if all i had to do was put $7 worth of fuel system cleaner in the damn thing. ill be happy at the same time..but oh so frustrated too.

maybe i just got lucky. several days of driving will determine that. ill keep you posted. thanks for the help so far from all of you that pitched in.

[Rootie524]

drove my car today for about 30 minutes on a sort of twisty road so there was quite a bit of acceleration and deceleration. first 25 minutes the only problem i had was at a light, when i sent to start acceleration it stuttered for maybe 2 seconds and went away. then all was perfect. on this one straight away i even got on it and didnt have a problem. then maybe 5 minutes from my destination, it stated f-ing up again! i dont get how it can be pretty close to perfect and go down hill at what seems like a flick of a switch.

this has to be a fuel problem. it just has to be. spark is fine and it has a brand new coil for the 4th cyl. so either my injectors are dirty or the fuel just dribbles out sometimes. so ill let my tank get empty so all the fuel cleaner goes through..but something tells me ill still have an issue.

also..when i did the compression test all of the spark plugs seemed to have a bit of oil on the threads and were kinda black. does that have anything to do with the signs of a problem?!