Trying to figure this out *Solved*
 

Hey everybody looking for some input on what my issue might be since I am completely stumped on this one.

Alright so a few weeks ago I was driving home from work and I had a 1/4 tank of fuel. I came to a stop and made a right hand turn and it sputtered out and died. Pull off the side of the road and I got it going again. Drive a couple miles to slow down and make a left turn slowly it didn't die. But after I made the turn I would get on the throttle and it would hesitate/stall/stumble like it wasn't getting enough fuel. So I get to another stop sign to make a left hand turn and I make the turn and it dies in the intersection! Bad situation to be in. So I get it off the road and get it running again barely. So I go on my way and I could barely get it up to 55mph and I had to very gently ease on the throttle to keep it moving. So I get to another stop sign in town and make a left hand turn, dies on me again! So now i'm just getting worried with whats going on mechanically. I end up limping it along to the gas station and fill it up. After I filled it up I took it around the block and MASHED on the pedal and the problem was gone (Or so I thought). I get it home and take it to work the next morning and now the throttle won't even rev past 2500 rpm's without hesitating/cutting power to the engine but I never lose ignition power. So I get it home and tear into the MAF sensor, clean that up check the vacuum lines, and all the way up to the throttle body clean it with throttle body cleaner. Then disconnect the battery incase their are any codes stored. Take it for a 10 minute drive a few hours later and its doing the same thing. So the next day I buy a new fuel filter and that friday night I took the old one out and blasted a good amount of sediment/rust/gunk out of it. Put the new one in and for about 5 minutes it was fine but I could feel it was losing power right around 4K rpm as I gave it the beans. Then that was short lived and it was back to its old limp self. A few days goes by and I removed the new fuel filter and blew back through it and reinstalled it yet again only a temperorary fix. So I recently discovered how to hook up to the fuel system a simpler way through the fuel line before the injectors (posted thread). So now at idle it has 42-44lbs of pressure which is good? So I take it for a test drive with the pressure gauge hooked up and It holds 44lbs steady up until about 3500-4Krpms and the pressure drops to 18lbs but only this time for some strange reason I was able to get the revs up but was still hesitating at wide open throttle just not completely cutting out like before. Sorry I know this is a long post but I would think if it was injectors it would be throwing a code, also if it was spark plugs same thing. I'm thinking its gonna be between the fuel filter and the fuel pump? If it was the fuel pressure regulator the pressure would be going bonkers the whole time and not hold steady..I'm at a loss because I maintain this thing like no other.
My other guess is maybe the throttle position sensor? Just odd it was running fine up until that one day and all of a sudden it takes a turn for the worst. Odd thing is it hasn't thrown a check engine code and I've gone through about a half a tank of fuel to try and diagnose what is going on. I've pretty much covered the intake/vacuum line side of things.

Anyway any input is appreciated. If I end up resolving it I will let everyone know.
Cheers and have a good weekend!

That's an odd situation. I would be leaning towards replacing the fuel pump. I agree that if the fuel pressure regulator was bad it would present itself in a different way. I wouldn't depend on the ECM detecting and throwing a code. I had an intermittent misfire that turned into a nearly dead miss that never set a current or pending DTC. Are you able to look at your fuel trims while losing power?

If you fuel filters were super dirty. Like bad luck suggested. Start at the tank. Make sure your line is clean from the fuel rail to the tank. I am really suspecting the screener in the tank to be plugged or fuel pump to be a mess. With the ethanol fuel if that vehicle sat for a few years sometime in the last 10 years. The inside of the tank might be rusted making a mess.

The fuel pressure wouldnt be going crazy like you seeing if the fuel was flowing freely.

The gunk in the fuel filter is the clue that your tank is a great place to start investigating.

Sent from my SM-J337V using Tapatalk

Well my speculation is the PO did not take good care of it at all probably a few years of its life before I had gotten ahold of it. I am pushing 221k which is a lot to expect out of a fuel pump. If i'm gonna be replacing the fuel pump screen I might as well replace the whole fuel pump assembly at that point. I got my pressure gauge hooked back up and I am gonna hook my scanner up to it while I drive it. Its hooked up ahead of the fuel filter right now. Gonna take it for a drive and see what my pressure is at during idle/acceleration see where its at. Then once it cools down hook it up before the fuel filter and see what my pressure is there. Thank for the reply!

May seem an odd question, is yours 5 speed or auto?

The fuel filter that I had previously removed was one I had replaced roughly around 190k ish miles so it only has 30k on it but I did get a lot of junk out of it. Also after I put the new one in I pulled it and blew it out and it had some small tiny pieces of sediment in it. Although it did seem to help for that time I drove it after that. Seems to be the fuel pump/screen has a lot of crud built up and it's restricting the fuel flow. Whats odd to me is the 2 ft of fuel hose I added to use the pressure gauge seemed to be the "fix" because once I removed it and put everything back the way it was it wouldn't rev past 2500k. Also forgot to mention if I shift it manually and slowly ease on the throttle it will slowly climb past 2500 but I don't like to do it due to the fact it's just rough on the engine/drivetrain to rev that high without shifting on its own. If I throw it in neutral and give it throttle it'll rev up like no tomorrow, but as soon as I put a load on it (in gear) it won't rev up worth a crap. Gonna take it for a drive and see if I can manipulate it with the gauge hooked up. Bring it back and clean/blow everything out again to see if the filter is clogged up with gunk yet again. If it is it looks like the fuel tank is gonna have to come down..Yay! living in the rust belt makes that a joy to do!
Thanks for the input!

Auto. I've checked the trans fluid/radiator tank and the fluids are the color they should be. Yeah I checked that first thing...Don't want any strawberry milkshakes going on. Also the radiator was replaced by the PO for prevention of the chance of that happening.

I had a similar sort of issue where i would lose power and the engine would die out at low rpm's in 2nd. yours being auto i doubt it would be the same issue. maybe try cleaning the injectors with a seafoam treatment. could help break down some garbage in your fuel lines too if youre having trouble finding it. ive also found the 5vz really likes 89 or 91 octane. Good luck!

I would drop the tank and do a thoro cleaning and since it’s down replace the fuel pump.

The inlet screens of your injectors probably have sediment in also. I’d also consider pulling the injectors and replacing the inlet screens. My 97 project thread walks you through how to clean them at home and rebuild them.

You could try putting two bottles of dry gas in the tank or 6-8oz of acetone. Both absorb water and the acetone will also help clean the system.


Sent from my iPhone using Tapatalk

Sounds like you might have a little water sloshing around in the bottom of your tank.

The fuel pump has a pre-filter "sock" which apparently can get clogged with sediment when it sloshes around with a low tank. You have to drop the tank to get to it though.

Odd thing is I put 89 octane in it to see if that would straighten out whatever the heck was going on..Did you ever figure out what was going on with yours?
I've run complete tuneup/B12 chemtool through it. It's probably been at least 10-15K since I had done that so I might give it a shot again. Thanks!

Yeah I think thats gonna be my best option at this point. Not sure about the fuel injector screens. Odd thing is everytime I take the fuel filter out and blow it out it temporarily fixed it, then it all seems to get drawn back to it. I've got roughly half a tank of gas to siphon out before I drop it. Thanks for the input!

Always a possibility I suppose or I just got a batch of bad fuel.

Yeah I am completely aware of the fuel pump screen. I ended up buying one from advance to replace it but then decided to return it. Due to the fact that if I go that far to replace that I'm just gonna replace the whole fuel pump/filter. Already got a cart of parts ready to order. Thanks for the input!