120k, recent tune up, cars been running great till last month.

I have a weird problem that i can't pin down. Starting last month, when the car is cold, it starts running weird. Like while i'm accelerating, it will bog down, and run like shit, unless i give it over 3/4 throttle. Then it kicks up and starts running fine. It usually does this for like 10-15 minutes when it's cold. But if the CEL comes on, it stops doing it. The code it's throwing is 43 (Fuel Supply System defective or malfunctioning fuel supply system). As soon as the CEL comes on, it starts running fine, and doesn't do it again untill the cars sits for awhile.

First i thought it might be fuel filter, so i changed that. Then I changed the fuel pump last night with a walbro 255 pump, and this morning it did the same thing. I'm kinda lost on what to check next, and it's weird because sometimes it runs fine. Any ideas?


Oh car has new O2 Sensor, I/H/E/C, Iridium plugs, and Accel wires.

 

so i jus checked the codes again and it's throwing 1 & 43. 1 is O2 Sensor, so maybe that's what is causing this shit. I replaced it like 7 months ago....hmmm...

 

fuel supply could just be a dirty filter, ive seen that happend before.

Could also be many other fuel components, but I mean thats the one that people dont think of

Kinda OT but how hard was the walbro to install?

 

yeah i changed fuel filter first.

the walbro wasn't too bad. it was a pita trying to get the hose clamp off of the return line, but once i got that off, the rest was pretty simple. should only take 30-35 minutes if you don't run into any problems. h:

i kinda struggled gettin my back seat out too, but i finally realized there was a bolt in the back. :doh:

the walbro is pretty loud though. i can hear a constant whining coming from it. i noticed slightly better throttle response too, (when the cars running right).

 

Have you checked the plugs to see what they look like?

 

no, but they were just replaced about 4k ago. :dunno:

 

i had the same exact problem with my LS it ran so bad when it was cold, and i had to give it a lot of gas or else it would bog out. i never found out what the problem was, but after about 2 weeks of this i ended up bending a valve and had to have a head job done and then it stopped

 

That's not what I'm getting at. I'm talking about checking the plugs to see if you're running rich.

 

if it's giving you a CEL, fix the problem. it may be as simple as the ECU jumping in and out of Limp home mode or getting some signal from the O2 and trying to use it...

 

Recomendations: check the plugs to see the condition of the inside of the engine, see if your running ritch, whats ur exhaust look like? A new O2 sensor can go bad in one day, also if you have a blown valve seal it can gunk up the sensor, the symptoms of that are blueish smoke. Another easy thing to check is your injectors, take them out and inspect them, or replace them with bigger ones since you have a higer flow pump.... Also check your gas, it might be contaminated.

Ummm Also the plugs you have in, when did you put them in and what did you gap them at? Sometimes older engines dont like the spendy plugs, I know my car ran like shit when I put the Iridium plugs in, so I changed them to the NGK V race plugs.