Need tuning help!!!

vortech306 · Oct 16, 2004

Lean Condition help

I keep pulling a code I believe 91 that says that the O2 sensors are always reading lean. Also, the car will studder at times. The motor was just put back together its got Edelbrock 6025 heads, Performer intake, crane 2030 cam, and A-trim blower. 1.7 rockers also. Fuel consists of a 255 pump, areomotive FPR and 30# injectors. Also the fuel prussure reads about 42 pounds. Im not running the FMU. What can be causing this lean condition? Also, the vacume is only at 8 hg but I cant seem to find any leaks. Please help me out with any advise.

autoXr1 · Oct 16, 2004

vortech306 said:
I keep pulling a code I believe 91 that says that the O2 sensors are always reading lean. Also, the car will studder at times. The motor was just put back together its got Edelbrock 6025 heads, Performer intake, crane 2030 cam, and A-trim blower. 1.7 rockers also. Fuel consists of a 255 pump, areomotive FPR and 30# injectors. Also the fuel prussure reads about 42 pounds. Im not running the FMU. What can be causing this lean condition? Also, the vacume is only at 8 hg but I cant seem to find any leaks. Please help me out with any advise.

What have you done to recalibrate the computer for your mods?

vortech306 · Oct 16, 2004

Computer is stock

autoXr1 · Oct 16, 2004

There 'ya go.

Simply changing a "calibrated" MAF is only one part of the tuning process. It'll get you up and running, but your stock computer calibration is still for 19# injectors, stock exhaust, intake, heads, and so on. Now, your computer does have a certain amount of adaptive control, but with heads, blower, 30# injectors, etc. it just can't meet the demands of the new combo.

So, that said, start looking for a reputable tuner to burn a decent chip OR start shopping for a PMS, TwEECer, etc. and a wide band O2 sensor.

In the mean time...be very careful. An untuned blower combo can be a bomb...especially without the FMU.

For further info you can visit www.stangtuning.com Pretty good group.

vortech306 · Oct 16, 2004

I know that there are ways to tune the car without having a chip burned. I have seen many people do it. I think that there is a problem that is more then just a computer. Im wondering, what can cause a lean condition overall. What are some possible causes? Does the low vacum have anything to do with it?

autoXr1 · Oct 16, 2004

vortech306 said:
I know that there are ways to tune the car without having a chip burned. I have seen many people do it. I think that there is a problem that is more then just a computer. Im wondering, what can cause a lean condition overall. What are some possible causes? Does the low vacum have anything to do with it?

Low vacuum can cause lean issues if it is picking up unmetered air. However, you might also have idle quality and other drivability issues. The question is, is 8 of vacuum appropriate for your cam and the effect of the blower?

You know what? I just realized you have an '88. Is this a speed density car? California '88 mass air car? Mass air conversion?

If your car is speed density, then I'd post your question on the www.corral.net "EEC tech" forum and/or the www.stangtuning.com
"General tech" forums. Speed density tuning is a little unique and unfortunately, not many know how to dial these cars in the right way.

If your car is mass air, then read a very good tech article called "Induction Blues" by Mike Wesley. It's on www.mustangworks.com. Click onto the "articles" page, then "electronics" and then "Induction Blues".

vortech306 · Oct 17, 2004

The car is California mass air, I will check out that link and see if it could help. Thanks.
Also, with the vacum that low, how can I keep the power brakes working?

autoXr1 · Oct 17, 2004

vortech306 said:
The car is California mass air, I will check out that link and see if it could help. Thanks.
Also, with the vacum that low, how can I keep the power brakes working?

When you did your measurement...did you take it off of a small vacuum line, or one of the larger ones? It makes a difference...like about 3-4 Hg in my case...the smaller the I.D., the more the pressure is dampened, and the more inaccurate. In addition, was the measurement stable, or did it bounce around? I'm not sure what the effect of having a certain amount of positive pressure (albeit low) at idle would have on your vacuum readings.

Ray@VSK · Oct 17, 2004

I'm having the same problem as you bud, I have to set my fuel regulator all the way open just so it's not pulling code 91 & that's with a 190lb pump, what I've been researching & troubleshooting I've found out that the only real option since I've found no problems & have replaced just about everything is "if your fpr isn't doing it for you" a EEC Tuner or what the Dyno shop recommended a Pro-M Optimizer.

vortech306 · Oct 17, 2004

I have a boost gauge hooked up to a large vacum outlet and it reads all the time. It stays steady. Do any of you guys with cams have trouble keeping your power brakes at idle?
Also, I guess I will try to crank up the fuel pressure and see what happens

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