sc3boost

Before i get all the hate mail about search, i think you shoud hear me out.

i have a 92 sc300(5spd) with a cold aid intake,msd ignition coil,electric fans,2.5 exaust, gutted cats and the stock muffler. recently i had hesitation so i got new plugs and wires, coil, and distributer, it ran good for a couple thousand miles, i'm at "78000 miles right now".
now if my tank is full car runs fine, and once the gas reaches a little below half the car goes untill i try to accelerate, then it hesitates for a while "really bad" like i have bad plugs or something and then it goes no problem, but when i full the tank back up hesitation goes away, and also when it is hesitating i idle at 1200-1300 rpm
here are some of the things i did to try and stop it ...............

empty the tank and fill it back..........i use 93 all the time
cheak the plugs and wires
cheak the spark plugs
cheak the timing
reset the ecu( left the battery off all night )
used injector cleaners
use octane boosters
i'm starting to think it is the fuel pump or a problem with gas tank or fuel pressure of something please let me know what you guys think or if it ever hapend to you

thanks

hwallen172

With a car of that age with relatively low mileage, you may be looking at contamination in the fuel tank. Rust or debris may be blocking the fuel pickup at low gas levels. I have a couple of "shadetree mechnic" ideas that you might want to try before the difficult and, let's not forget, dangerous job of getting into the gas tank. The first is pretty simple. Get some of the alcohol based fuel drying additives that are designed to eliminate water from your gas and try that. You're going to think the second idea is a little crazy, but bear with me. Go to a hardware store and buy a strong magnet that they sell for picking up nails. Stick it to the rear bottom corner of the gas tank and fill up the tank. If rust particles are your problem, they will migrate to the magnet and quit clogging your fuel intake. If not, hey, you got a new magnet. Impress your friends.

sc3boost

thats the most creative answer i've got since i been asking around, shame on you for thinking you're crazy,i'll try it .
and also will a cloged fuel pump cause the high idle??????

HotBoy

I don't know man it sounds like it is a fuel problem, what about your TPS did you check that ? I am just throwin things up in the air. I am assuming there is nothing wrong with your air filter as it is a cold air intake. Sounds like you have allready narrowed it down to fuel though. Good luck.

sc3boost

personally i have a gutt feeling that it is the fuel pump, but i'm not ruling out the tps, that little thing is a pain in the a$$,but with a full tank it runs fine so tps is sort of 10% on my mind, it can't be the fuel filter cause i changed it last month.
what about the fuel pressure regulator or the injectors, maybe with the tank half i lose some pressure or something i don't know.
will a cloged or old charcoal canister cause this???????????????

hwallen172

I just remembered a problem that a friend of mine had with a Volvo that is similar to yours. It would run fine on a full tank, but at about half a tank, it would act up. Turns out that the fuel pickup tube had come off the fuel pump. He pulled the pump and replaced the tube and everything was fine. If your problem happens at the same fuel level every time, that could be the cause. I don't know how to access the fuel pump in the SC300, but I'm sure someone here does.

A problem with fuel delivery could cause the computer to vary the idle to compensate. It's pretty easy to irritate an engine control computer, and messing with fuel or air is a good way to do it.

Bean

iTrader: (1)

i've got a post out there on how to replace the fuel pump in the SC300; not hard at all

sc3boost

the fuel pump is not hard at all, and if all is lost i have the grey bible to fall back on.
the fuel pump is located either behind the rear seat, just lift out the back part of the seat, and there is a panel there, just remove it and it's right there, and if you go in the trunk and take off the panel under the rear window there is another one there.

don't hold me to it but i know one is the fuel pump, i'll look it up and tell you if you really wanna know.

sc3boost

hey thanks alot guys but i figured out the problem, believe it or not it was the maf sensor, i changed it today and it ran like i just bought it........

sc3boost

sorry guys but i think the new maf helped but it did'nt stop the problem, it idles fine right now but, since i put it back together, it smoked once but not as bad as before, and a little hesitation, like one cilinder is not firing, i'm leading towards the ignition, but if the car is getting to much fuel should'nt the smoke be black.

heres how it goes idle is no problem, even if it's puffing white smoke, the idle stays below 1000k rpm but when i rev the engine it feels like it is missing very bad.

hwallen172

This is a tough one, dude. Yes, overly rich fuel mixtures will cause black smoke and deposit soot in your exhaust pipes. White smoke is typically coolant finding its way into the cylinders, most likely from a head gasket problem. Neither of those issues should be related to the level of fuel in your tank. The MAF replacement is also independent of the fuel level. I know that you mentioned that you checked your plugs, but you may want to reexamine them to see if this problem is isolated to one cylinder or related to a control system problem. I know that a plug in a too rich cylinder would be black and sooty, but I'm not too sure how a plug would look if coolant were getting in. Maybe someone else could chime in on that point. In any case, I think it would look different from the good plugs. If you are looking at a control system problem, I would think you would see some check engine codes popping up. However, you haven't mentioned that.

I'm sorry that I don't have any specific answers to your problem, but I hope that I have given you some help in troubleshooting it. Just stick to the basics, fuel, air and fire.

Good luck,
Wiley

sc3boost

hwallen172

thats the point, and it has been pissing me off for a while now that i get no check engine light, when i think about it it's kinda funny that i actually want my check engine light to come on
now i know it is'nt coolant cause i check it all the time and there is never any coolant or oil loss, see why i'm pissed off. i think the ignition system is the final straw

sc3boost

ok guys listen to this ****, i pulled the first two spark plugs and they were fine, so i left is alone, so the car acted up again and at the same moment my wife pised me off

sc3boost

ok guys listen to this ****, i pulled the first two spark plugs and they were fine, so i left is alone, so the car acted up again and at the same moment my wife pised me off, and i don't know if i'm the only one who does this but when i get heated i take a LONG drive, or i just work on my car, so some how i ended up takeing off the f@#king anoyingass intake manifold and realised that the bolts on the inside of valve cover were loose pulled the plug and found that oil was on the tip of the plug in cilinder 3,4,5 and 6, so i cleaned it out tighten the bolts and took a drive, it got up to the ideal temp faster than usual and the idle was normal all the way through and the car picked up pretty quickly.

so in conclusion, i think this should solve my problem, so i thank again everyone who tried to help

sc3boost

guys please don't hate me for this but the problem came back and i think i may have narrowed it down.
help me figure this out and tell me if i'm right, the valve cover is'nt leaking, but it acted up again,so i looked down between the spark plugs again and there was no oil but the car still acted funny, and when i took out the spark plugs they were soaked in oil, now correct me if i'm wrong but does this mean i have bad piston rings, cause everything elese is perfect.

might as well get a new engine huh