GranVille-4crawler

Ok, I've read up on threads with similar symptoms but still can't diagnose my problem. About a month ago now I went out and bought my 85 4runner. Did basic tune up stuff. Pcv,plugs wires, fuel filter, o2 sensor etc. My truck runs like it just rolled off the show room floor when the gas is full, runs great until right above 1/2 tank. Once it hits this point when I try to accelerate it bogs sputters and wants to cut out. I've done 3 treatments of sea foam in the vacuum system and gas tank and still it does it. Any ideas?

Kiroshu

When did you do the sea foam before or after.... Sea foam i've done on 4 trucks and it caused this sputtering problem... aside that its not always true for everyone and everytruck but i void sea foam..... Try tapping on the top of the charcol canister, theres a purge valve in there that maybe hung up. EGR valve? Unplug and drive see what happens. Dirty air filter? Check fuel pressure should be about 35 PSI.

GranVille-4crawler

Yeah all that's good. It only does it when the tank reaches half empty. I was thinkin fuel pressure. Maybe my pump is going bad and it doesn't push enough when it doesn't have the pressre behind it from a full tank of fuel. I've unplugged egr and all. Where is a good place to get a fuel pressure reading

myyota

Why don`t you remove the fuel pump assembly from the tank and make sure the fuel pump and strainer are still in good condition and properly hooked up, also, when was the last time the fuel filter was replaced ?, if its been a while i would give that a try.

low-n-slo

maybe you should try giving your truck to me and ill handle it.

Kiroshu

Tap a line in at the main line coming out of the fuel filter.... if you have a tester gauge... if not you may just have to play parts replacer or take it to a shop and have them check fuel pressure if its not about 35 your fuel pump and or filter are bad.

GranVille-4crawler

yeah and then you could give me your jeep NOT

GranVille-4crawler

Also its more prone to doing it after I've been driving for over 10 min or so

Kiroshu

Initial fuel pressure can be high but a failing fuel pump or clogged filter can have this effect... unless theres a low voltage drop somewhere... but not likely.. you need to to do what i told you and nothing more

GranVille-4crawler

Will do this weekend and come back with an update

GranVille-4crawler

Ok so my fuel pressure is fine, and today on my way back from doin a little wheelin in spartanburg sc I had a full tank of gas and still the sputter thing. The worst drive I've had. I found that if I turned the car off and then restarted it the sputter would disapeer for about 10 miles or so. I'm lost on this one... any ideas

myyota

Im just throwing out some ideas here, try checking the TPS, if its going bad it could cause a miss or sputter, also check the oxygen sensor, if its going bad it could be sending the wrong signal to the computer causing a lean miss (sputter). These are all just guesses on my part, but these parts can cause the problems your having if and when they start to go bad.

GranVille-4crawler

Yeah I replaced the 02 sens when I bought the car along with all the other stuff wire plugs filters. I was kinda thinkin tps but I hope not those things aren't cheap! Its just really weird cause its like whatever it is that's messing up gets reset when I turn it off and restart.

myyota

Has it always this since you have owned it ?. The only other off the wall thing i can think of is to check the gas cap, it should be a vented cap, if its not then replace it. The next time your driving your truck and it starts to sputter, pull over but don`t turn the truck off, remove the gas cap and see if there is a lot of presure built up in the tank. Leave the gas cap off and drive a little ways and see it that solves the problem.

GranVille-4crawler

Yeah ever since I owned it didn't really notice it right away cause it first started doin it around 1/2 tank except for today. The cap is a vented one and it looks semi new, its def not the orig.

Kiroshu

I had an issue similar to this on another truck i had. turned out the purge valve was stuck. When the truck is running try taping on the top of the charcoal canister where the inlet and outlet are. A faulty opeing too early egr valve can have this same affect... The purge valve could be stuck. PCV valve ok? Try the gas cap it could very well be defective causing this. Usually not with older 22r's. Usually a gas tanks fuel lvl does not have an affect on driveability unless of course its empty... When does it seems to hesitate? Certain speeds rpms? Did you acctaully take the vac line off the EGR like i told you a drive it?

yotaman85

fuel tank isn't venting, take the fuel cap off and see if it goes away.

GranVille-4crawler

It will hesitate at any speed whenever I try and give it gas, I've replaced the pcv valve. I will unhook the egr line before I go in to work tomorow and see if that does anything. And I haved banged on the charcoal canister to see if the purge was stuck. The egr line is the big one going to the intake mani from the head correct?

Kiroshu

Do you know where the EGR valve is? Its on the back of the intake manifold. Its a round flying saucer looking device. The vac line going to the top of it. Just unplug it and let it hang it won't hurt. So things you need to try going to work tom.

Unplug EGR valve vac line.

Take off gas cap.(As many others mentioned)

Try these things and see what happens.

GranVille-4crawler

Sounds like a plan. Let you know the outcome tomorow thanks