Car started running lean the other day, can't seem to figure out what's going on.Run a pt-51 , v-2 front mount, 50 # inj., rjc plate, 340 walbro, exhaust and ans boost controller. Was running 20 lb.boost on 93 octane mils in the 812 range. Now I am getting knock 4-5 deg. at 17- 18 boost. Changed heated o-2 to reg. o-2 sensor with new sensor because of several passes a few months ago with leaded race fuel. Running 42-43 lb fuel pressure also. Adding fuel doesn't help either. Changed gas stations numerous times. Can't get consistent milivolt readings either. They range from the low 700's to 870's. The car used to get a degree or two of knock when you first mated it and then went away .Now i am getting way rich early on 880-900 no knock, then leaning out on top end 760-810 4-5 deg knock. Also have a modified bosh reg. that according to my guage moves around 2 lbs. now.Could this cheap o-2 sensor be causing this, fuel reg.,chip, computer or what. Please HELP!
tuning nightmares
- Thread starter kevinw
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Cheap stuff first.
I know it sounds basic, but have you checked your fuel filter lately? That's where I would start. If that doesen't fix it, you could call it preventitive matainence and justify the whole $5 it cost.
After that i would be suspect of your supply. You said the gauge mover about 2 psi, is that total, or just when you are sitting still. Your fuel pressure should rise with boost. For example, If you are running 42psi line off and 15 psi of boost you should be seeing 57 psi at WOT. Good luck.
I know it sounds basic, but have you checked your fuel filter lately? That's where I would start. If that doesen't fix it, you could call it preventitive matainence and justify the whole $5 it cost.
After that i would be suspect of your supply. You said the gauge mover about 2 psi, is that total, or just when you are sitting still. Your fuel pressure should rise with boost. For example, If you are running 42psi line off and 15 psi of boost you should be seeing 57 psi at WOT. Good luck.buickfreak
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- Sep 11, 2002
- Messages
- 289
YOu are right , lots of boost with cooler air charge and running not enough OCTANE .
The problem with the guage reading is when i set it at a given pressure say 42 lbs and mat it two or three times you can check the pressure on the guage and it will be a couple of pounds higher or sometimes lower and you have to re-adjust it. Yes it is getting cold here in North Carolina but I have ran this car for two years in temps this cold and never had a problem with it going lean especially at 17-18 lb. boost.I still can't get consistent miliviolt readings and this has done this within the past couple of weeks. I first thought it may be bad gas but I have run 20 gal. or so through the tank and I don't think that is it.
