I have lb9 engine 91 and i have about 15 mpg in city and 20 mpg on highway. Is it normal? The spark plug, distributor, timing, cap and rotor are new. I set the timing at 8 deg. The o2 sensor give .2 to .9 volt. The o2 sensor is it necessarily good if the voltage up and down rapidly??

thanks

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trans-am 91 3.08 posi 5.0 lb9 5 speed stock

 

help me please!!!

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trans-am 91 3.08 posi 5.0 lb9 5 speed stock

 

To check for a leaking injector get a fuel pressure reading and see if it bleeds off. If it bleeds off some inside of 20 minutes a leaking injector is one of the possible problems. When was the last time you replaced the O2 sensor?

 

never. i bought the car last month. The reading of the o2 sensor are good and i have no computer code.

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trans-am 91 3.08 posi 5.0 lb9 5 speed stock

 

I changed my 02 for the hell of it and got 3mpg better!
My hesitation problem is still there though just after idle (when slowly accelerating).

 

Ignition module can be the source of hesitation. It was in my case. How many miles on the engine?

Check the voltage of your TPS sensor. Set it at .54volts ( i think thats stock voltage)

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91 Formula
305 TPI 5speed
1LE/G92/WS6

Paxton SN92 polished kit, SLP airfoil, ported/polished plenum, March pulleys, Crane AFPR(43psi),Crane Gold 1.6rrs,MSD coil,MSD6AL,MSD boost-master,Holley 9mm wires,Ac delco R43ts plugs,custom chip,Ford SVO 24# injectors,Bosch O2sensor, Bosch in-line pump(w/stock pump), SLP 1 5/8" headers,SLP catback,short shifter,3:73s w/Auburn posi,170* t-stat,JET 195* fan switch, Macewen white face gauges, Autometer gauges, Zoom hi-performance clutch.

 

My motor have 60 000 miles. Is it posible
that the winter can cause my car run too rich???

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trans-am 91 3.08 posi 5.0 lb9 5 speed stock

 

I know in the winter I seem to get slightly worse gas mileage, especially when its close to or below freezing. I think this has to do with air density, you know, like drag racers like to run when its cool out. It wouldn't hurt to change your o2 sensor, just because the numbers are good doesn't mean their right if you know what I mean.

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'87GTA w/ SLP Cold Air, MSD Coil, Airfoil, Gutted MAF, AFPR, TES Headers, HI-FLOW CAT, Flowmaster Catback, Energy Suspension Master Bushing Kit

 

Set your timing back to stock (6btdc) as well as your TPS sensor. Adjusting timing by turning the distributor is not the way to do it on FI. Now a days , the proper way to adjust timing advance is with PROM work.

How is your power past 3k? When was the last time you used throttle body cleaner to clean out all the gunk in your Throttle body and plenum?

 

I dont know for last owner, but for me never.

On the edge of the trottle body, there is black powder.

Maybe it will be useful to use cleaner.

Past 4000, the power is not good.
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trans-am 91 3.08 posi 5.0 lb9 5 speed stock

[This message has been edited by stallone (edited February 27, 2001).]

 

Definitely clean the throttle body blade seating surfaces with a can of throttle body (NOT Carb) cleaner. Also be sure to change that O2 sensor if you're not sure when it was changed last, or at least pull it out and see if it looks fouled.

 

Checking for a leaking injector requires a fuel pressure gauge attached to the fuel rails and the squeezing of the pressure and return lines.

Squeezing one line identifies the cause as the pump and squeezing the other zeros in on the injector.

If you need the step-by-step shoot me a line.

Jake

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1986 Corvette Coupe, 415 CID, Edelbrock 6073s, ZZ9