Hey guys! I don't post too much on here because I usually don't run into many problems I can't fix, but when I can't, I find this a great place with lots of knowledge, this is one of those times.I searched and couldn't seem to find anyone with the same type of problem.

My situation is that I have a 89 Firebird Formula 350 5.7 TPI, its got less than 10,000 miles on the reman roller motor, I bought it last spring like that. Its my fast fun summer DD. Redid the whole suspension and everything over the winter and one of the other things I put on it was a Stoichmeter. Now it runs great doesn't stall or anything like that, no bogging or anything, stoic constantly switches from lean to rich while cruising and what not, just like its supposed to, and when I give it gas goes rich, like it should. Now last night I got on the freeway and started going a steady 70mph and the gauge goes so far lean that's its not lighting at all, and it did this till I gave it throttle or till I started slowing down to get off the freeway, it did it on the return trip on the freeway too. Now my gauge is not a wideband, just basically a light show type, car seems to run fine even when the gauge says extra lean, doesn't get hot or anything. I also get no engine light or any warning lights, all gauges are in appropriate areas.

My question about this is, does this seem normal according to my symptoms? Am I just paranoid because of this stoichmeter? Or might there actually be a problem? My big concern is because even though 95% of my driving is city, 55mph and below, I am planning to take a trip in the car down to Tennessee in august, and I want to make sure the car is good to go. Any thoughts and insight would be greatly appreciated

Heres some specs on my engine. My timing is advanced 8 degrees, I know standard is 6, brand new oxygen sensor, shorty headers with y pipe, no cats.

 

During cruise the egr opens and leans out the air fuel mixture. If you have the original Multec injectors it would be wise to replace them with southbays Bosch 3's.

 

You mean the less expensive Autozone light show gauges? They are not accurate at all and usually a go/nogo gauge for AFR if that. I would say you will be lean at that cruise speed and be in the 15+ range and no issues. Your wideband is only 0-1V and it only responds in last .3 volts like .79-.99 range. After that it drops off or pegs out at 1.

A wideband will give you the resolution and accurate results.

14point7.com sells a great unit wideband that supports all aftermarket systems and has analog output to replace your stock o2 as well as wideband output for you to monitor or datalog. It is only $140 for non datalog I think and $200 for datalogger

I installed one on my 300zx turbo and trouble shoot fuel issues. What it allows me to do is offset the narrowband output to dial in your fuel curve (slightly)

In my case I was running rich even after tune up vac leak checks etc. It was some injector worn and notorius MAF issues and blow by from turbo.

I couls see I was running lean all teh time then pig rich at idle.

Replaced MAF
Adjusted idle
Then offset MAf signal by .1 volts

and my AFR sat at 12.7 for WOT and speed and I cruised at 15.1-15.6 no throttle load on hiways

Then I dialed my boost levels in to keep the same AFR ( I used a great little boost meter as well that was programmble for the boost)

Simple tool and made my awesome and driavable.

 

I would say that it would be true that the egr opens up, but it has an egr delete plate, no air pump on the car either. I was planning on replacing the injectors soon, in fact the cam, heads and lower intake setup is going to be replaced over this next winter, and I was going to do them then, however I believe that the south bay Bosch 3s are just 22lb stock injectors, correct?, due to future plans, I am looking for a set of 24lb injectors so that I won't have to pull everything down again.

Now at highway speed, the car I know should lean out, I got the gauge from a buddy, but I didn't think that an autometer gauge would be that far off, but oh well, originally I put it on because I thought it was constantly running rich, but that wasn't the case. Still, I may look into a better one, its just nice to know.

I also seem to get really crappy mileage from this car, like maybe 12mpg, I thought that this car should be getting at least 16 ya know?


Edit! I checked out south bays site and apparently the Bosch III are 24lbs, my mistake.

 

Southbay bosh 3's 22#hr are refurbished for 19#hr but at 3 bar they flow 22#hr.
Have you disabled the egr and air pump functions in the programing ?

 

I am not 100% sure if its programmed like that, i bought the car like that. Now I do know that the engine light works and everything, however it does not come on at all unless a sensor is unplugged or I'm timing the car.

 

I think I found my issue, my alternator went out on me the other night, and when I noticed something wasn't right, I happened to look at my gauge and it wasn't working at all. Put a new one on and now it works on the freeway. However I have one more question. It should just lean out and sit there at cruising 70mph, but it just switches rich to lean like its looking where its supposed to be for optimal stoic, but never finds it. Any ideas?

 

The O2 sensor should constantly switch from about .200 to .800, except on decel(fuel cut off) and hard throttle(accel enrichment). This the normal function of a narrow band O2 sensor. On a scope it should look like ocean waves.

 

Thank you I knew it should do everything else, just wasn't sure if it was also supposed to switch while cruising 70, thanks for clearing that up.