My car started to lean out 3 days ago while cruising. It does it between 1500 and 3000 rpms, after the secondaries activate the problem goes away for a couple of seconds then it leans out slightly if I maintain half throtle. If I go WOT it doesn't lean out at all. My mods are rtek 1.5, full exuast, custom 3" tid, walbro fp, running 10-12 psi.

Note: I have a VAC leak that I haven't been able to find but it only bothers on a cold start, after the car warms up it doesn't bother anymore. I changed the fuel filter yesterday thinking it was cloged, no change. Pump was installed about 5 months ago but the car is only used on sundays.

Please help!

JP

 

anyone?

 

how are you judging that it's lean? wideband?
Generally, it's suppose to be a little leaner when cruising (not under boos) to help with your fuel economy. I've been told...somebody else can probably verify this.....that running between 14 and 15 to 1 air/fuel while not under boost is a good range to shoot for. Don't take that as fact tho...as that's just a figure I was told.

 

yeah but not to the point where its bucking while cruising

 

same question as ^

if you are using the narrowband sensor with a air/fuel gauge find a ricer and sell it to them, it's useless.

under cruise, stoich air/fuel is 14.7:1 which is a bit leaner than you want when going into boost. 12:1 up to 4-5psi is ok then 11:1 up to 12psi to be on the safe side.

 

I have a afr guage but not a wideband

 

toss it, it won't tell you much. sell it and put that money towards a wideband.

as far as your bucking is concerned, find and fix the vacuum leak, any leak is a bad leak. running that kind of boost i hope you have a way to add fuel such as a standalone or SAFC, in which case just richen it up. check the TPS as well, it sounds like it could be a bit off or completely buggered.

anything over 9-10psi with the stock fuel system = POP!

i hope you are not gambling with your motor.

 

ok i will get a wideband but it won't solve my current problem, trust me its leaning out ive gotten small detonations when the problem occurs

 

is this under cruise or WOT? i'm a little confused, you would have to be severely lean for it to detonate under cruise.

check your ignition timing also, it could be wayyyyy off which could also cause this issue.

 

ok ill check timming, it does it while cruising or half way throtle. I don't have any problems WOT at this time

 

I think i have a similar problem...It seems when i try to hold a constant speed...it bucks a little...

for example...if im going down the highway in my TII at 80 (3500 rpm) and i hit a slight downhill... i have to let off the gas a little to maintain that speed...so my foot is barely on the gas pedal...the car will buck...and i think thats what your talking about...i have the some problem and im gonna replace my injector grommets this weekend...maybe that will help...


-Matt

 

if I let off the throttle it doesn't leanout though. any other sugestions other than timming?

 

im gonna guess vac leak...lean=too much air ---- vac leak=too much air....

 

could a cloged injector or a faulty tps cuase this also? I'm just looking for as much input as possible before I start messing with it

 

I forgot to mention I cleaned the engine bay before this started to happen. Could cleaning the bay cause a sensor to go bad like the TPS or something?

 

^

What did you clean it with?

 

degreaser and some water!

 

I took off the IC last night and found the VAC leak, Thats fixed. I also found a sensor that was unpluged it goes on top of the UIM at the entrance . Anyway plug it back in and the car is still leaning out. Any ideas on what could be wrong?

 

its perfectly fine to run lean when your not in the boost, low load, i run 16.5-17.5 AF (on wideband) when around 60-80mph.

 

Hum, you said something intresting....

You said it doesn't lean out when you let off the gas ?

How do you know? Is it popping and backfiring when you let off the gas at highway speeds?

James

 

Im going by what I see on the a/f gauge. I know its not that reliable but its all I have right now. It bucks on me when the gauge goes from stoich to lean. For some reason after I cleaned the motor out it started this problem again. when I first bought the car about 7 months ago it had the same problem it turned out to be a combination of a bad FCD and boost sensor.

 

I'm going to replace and reset the tps this afternoon. I will update any change. Noob questions comming up: who makes wideband AFR gauges? which is the best one out there right now?

 

I installed a aftermarket fuel pressure reg. and its reading 22psi at idle with the adjustment totally closed and about 40 - 50psi WOT. I guess my fp is going out, have anyone had problems with the walbro pumps? I installed it a couple of months ago and I only use the car once a week.

 

Water + FCD or Boost Sensor could be your problem if it had similar symptoms with a bad FCD/Boost Sensor before.

 

I'll get another boost sensor and try it out ( can get them for bout $15 locally ) but I am still conserned about the fuel pressure is it normal, I was told it should be around 35psi at idle.