stock98gs

Hi, i am new to this forum and i am hoping you can help me. I have a 98 GS300. 170,000 miles i have owned it since 155k. as long as i have had it (and it has been getting progressively worse) on start up intermittantly the car will buck, jerk and sometimes stall. If you give it gas, the rpms will climb slowly at first but as soon as it gets above 4000 rpms it revs fine. do this a couple times and the car runs great. I had codes for bank1 and bank2 oxygen sensors and have replaced both upstream o2 sensors. I have replaced the MAF and replaced spark plugs (with toyota denso dual tipped plugs as lexus recommends). I still have lean codes p0171 but no p0174 which kinda throws me off but anyways. Just incase, yes i know this is a strait 6 2jz-ge and technically it only has one bank but this vehicle has 2 factory exhaust manifolds and it can tell a bank1/bank2 (front 3 or rear 3) difference. Also recently i noticed a small fuel leak by the tank and have yet to investigate further. If i have a chance to pull the fuel pump covers and look at the tank ill fill you in what i find. Any and all help is welcome and very appriciated! Thanks Jerad

DeanGS

iTrader: (8)

Clogged injectors, low fuel pressure (above around 3K the fuel computer sends a full 12 volts to the fuel pump, under that and at low demand the voltage is reduced) caused by a bad/clogged fuel pump or fuel filter.

tinman

He said that it smoothed out about 4K RPM. One would assume this wouldn''t happen if the fuel filter were clogged... but I have to admit, I have no alternative explanation.

Lexus827

seems to be like a fuel fliter i would also check the oil control value it my be clogged sounds weird but that could be it

stock98gs

Thanks all, i did swap the oil control valve and it still did it, so i can rule that out. Is there another filter other then the one on the pump that i am overlooking? Again thank you

KenMasters

I'd say fuel pump or fuel pressure regulator

tiger4life

iTrader: (16)

if you check the fuel pump assembly, be very careful. the 3 o-rings in the assembly would need to be replaced. i changed my filter recently and had to buy a used assembly for $100 today just because a little plastic washer between the pump and filter cracked. the cracked washer was allowing the fuel pressure to drop as the car was sitting for a while resulting in hard starting. i have a threadon here about the washer and where to find the o-rings.

dejavu157

iTrader: (2)

go get full tune up.

pga88

i agree sounds like a fuel issue.