For some reason my fiero seems to fluctuate between a lean and rich condition during idle(as shown by my O2 meter). See the video to see what I am talking about.
http://home.comcast.net/~jszczech1/turbo_run.wmv

Is this normal? I have had this problem even before I installed the turbo. I have tried different 2 ECMS/chips and the O2 meter still bounces from lean to rich during idle. I have installed a new:

TPS
IAC
MAT sensor
MAP sensor
O2 sensor
Coil
Distributor module
Spark plugs
Spark plug wires

and the darn thing still runs this way. Any ideas?

It should but I would expect it to do it faster. How old is the O2? Are the RPM's hunting? The boost gauge seemed to be steady as much as I could see.

[This message has been edited by TK (edited 11-15-2003).]

quote Originally posted by TK: It should but I would expect it to do it faster. How old is the O2? Are the RPM's hunting? The boost gauge seemed to be steady as much as I could see. [This message has been edited by TK (edited 11-15-2003).]

The O2 sensor is relatively new (installed it the same time I installed the rebuilt engine) with less than 8k miles on it. The injectors are also new, along with the fuel filter and pump. The engine rpms also fluctuates (about the same rate as the o2 meter) by about a few hundred rpm (if you turn up the volume in the video you can hear). Sometimes it seems like the engine is about to stall but then the rpms jump, settle and then fluctuate again. This has been a problem ever since I bought the car and the O2 meter really brought it to my attention. One other thing that I noticed is that if I slowly increase the rpms the engine runs lean and rough but then past 1/4 throttle it runs smooth and rich.

[This message has been edited by Leadfoot (edited 11-15-2003).]

[This message has been edited by Leadfoot (edited 11-15-2003).]

The fluctuation is of course normal as the ECM reads the O2 then flips back and forth. I think it's a touch on the rich side (safer!) when you rev it up and the boost comes up.. but then when it comes down and idles it's really lean... it's POSSIBLE that you're cooling the O2 down too much and it can't get a good reading.

You might want to try switching to a 3 (or 4) wire O2 sensor - they give a much more consistant and accurate reading because they're internally heated (you don't have to count on the exhaust to do it). Just ge t a generic one that's got the correct bung fitting - it'll have crimps on the lead ends. Hook the black wire up to the original purple lead that you cut off your old O2. Then hook the two white wires up to a switched +12V source & good ground.

Like I say - that might not be your trouble, but at least you'll then have a much more 'up to date' O2 sensor system.

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87/88 V6 5spd "FormulaGT"

My pages: http://www.fieroclub.com

http://www.fierohut.com

This is normal. If you switch to a HO2 it will be a little more accurate but not much. The A/F guage is to tell you aproximatly what it is at WOT only.

good luck
Kyle

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1988 Formula 2M6 5 Speed - CRX Intake, NOS dry kit, ZEX Ejector Air Amplifier, Taylor Wires, NGK UR5 plugs, MSD 6AL Ignition /w 2 step rev control, MSD Blaster 3 coil, WCF dog bone, WCF engine mount, Autometer Ultra-Lite guages (A/F,Vac.), KYB GR2's, Sequential turn signals, Rapid 3rd brake light....
Recurring donator

Seems awfully slow.

I have a hard time believing this is normal. I did a search and read that an o2 sensor can be slow but i thought that is typical of an old o2 sensor. I like the idea of the 3/4 wire o2 sensor.

I wonder how fast the gauge is responding to the signal from the O2 sensor. The one that I used was buffered so much that it was not good for anything except to be a novelty. Have you checked it with a digital volt meter to see how the real time voltage is relating to the gauge display?

Good call Cooter.

I have not checked the signal with a voltmeter. What I still don't understand why the rpm fluctuates as well. I wonder if I have to add another ground cable as I heard that a bad ground can reek havock.

I have the exact same gauge pack for my turbo setup (I'm guessing yours must be a KFG or Lagrua setup). Like yours, the A/F alternates between lean and rich at idle and cruise which is normal. The only difference I see compared to mine is that yours seems extremely slow. My A/F meter alternates much more rapidly. I also noticed after you stab it a couple times in the video it hangs one to two bars rich for quite a while and when it finally leans it hangs there for a while too. On mine, as soon as I release the throttle it goes one to two bars lean for a split second until the engine needs fuel to idle then its back to stoic and alternating. Mine also hunts idle in unison with whatever A/F meter says (lean/rich) until it stabilizes after revving. It happens very fast though and never tries to stall.

For comparative purposes, my fueling system is completely stock, stock FPR, injectors, and fuel pump and the O2 sensor is probably the original one. It's one of the few items I've haven't replaced yet. Oh, I'm also running a Lagrua remapped prom.

Good luck sorting it out...

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White 86 GT 5spd
2.8L Turbocharged V-6
Suspension Techniques 2"
Rear Sway Bar
KYB's

quote Originally posted by X86GT: I have the exact same gauge pack for my turbo setup (I'm guessing yours must be a KFG or Lagrua setup). Like yours, the A/F alternates between lean and rich at idle and cruise which is normal. The only difference I see compared to mine is that yours seems extremely slow. My A/F meter alternates much more rapidly. I also noticed after you stab it a couple times in the video it hangs one to two bars rich for quite a while and when it finally leans it hangs there for a while too. On mine, as soon as I release the throttle it goes one to two bars lean for a split second until the engine needs fuel to idle then its back to stoic and alternating. Mine also hunts idle in unison with whatever A/F meter says (lean/rich) until it stabilizes after revving. It happens very fast though and never tries to stall. For comparative purposes, my fueling system is completely stock, stock FPR, injectors, and fuel pump and the O2 sensor is probably the original one. It's one of the few items I've haven't replaced yet. Oh, I'm also running a Lagrua remapped prom. Good luck sorting it out...

Yup it is a kfg set up byt i added an intercooler) with an eprom from Dennis. Dennis mentioned that the ac delco o2 sensor has a faster reacion time compared to the bosch brand (which is what I have). My fuel system and ignition is stock but I replaced just about everything. I think I should use winaldl to see if anything is out of wack.

what kidn of fuel pressure are you getting at idle? it should be a constant 40+ psi

quote Originally posted by Leadfoot: I have not checked the signal with a voltmeter. What I still don't understand why the rpm fluctuates as well. I wonder if I have to add another ground cable as I heard that a bad ground can reek havock.

I installed an adjustable fuel pressure regulator. The fuel pressure is rock steady at 45 psi. I set it to both 40 and 50 psi and didn't notice any change.

Well I picked up an AC Delco O2 sensor (AFS20) and the car runs much better. By the way the Delcos cost about double the Bosch sensors. The added ground wire didn't make a difference and I haven't fixed the seal leak. I still have the rpm fluctuations but it is less severe +/- 200 rpm (I am beginning to think that this is normal). I guess my desire for a rock solid idle is too much to ask for. The big difference is that the car no longer stumbles when you slowly open the throttle to 1/4 open. My thanks to those that replied!

quote Originally posted by Leadfoot: Well I picked up an AC Delco O2 sensor (AFS20) and the car runs much better. By the way the Delcos cost about double the Bosch sensors. The added ground wire didn't make a difference and I haven't fixed the seal leak. I still have the rpm fluctuations but it is less severe +/- 200 rpm (I am beginning to think that this is normal). I guess my desire for a rock solid idle is too much to ask for. The big difference is that the car no longer stumbles when you slowly open the throttle to 1/4 open. My thanks to those that replied!

Try a MAP sensor from a 91 Camaro with the V-8. These are a little better reading pressure than the stock Fiero ones. This may also help the hunting idle.

UnF###kin believable! So I backed the car out of the garage and let it idle for a while to charge up my battery when all of the sudden it stumbles and dies. I tried to start it and the engine would catch but not run. I could smell fuel and was getting spark. After a bunch of farting around I found my problem. It's the G*****n! spark plugs. These Bosch platinum +4 bite the big one! I put my old plugs in and the car runs fine. I swear if it's not one thing it's another.

Oreif, are the MAP sensors on the 91 v8 camero 2 bar or 1 bar? I need a 2 bar MAP due to the turbo.

I just ran across article on the Michigan Fiero Club site last night.

quote Are your sparkplugs correct for your Fiero? - Submitted by Fiero Tech Advisor Floyd Dobson -------------------------------------------------------------------------------- Just a note on my experience with some of these "special" spark plugs that are available today. The Bosch Platinum +4 plugs are designed with special engine applications in mind. Our 2.5L-L4 and 2.8L-V6 are not designed to provide the combustion camber turbulance that the Bosch Platinum +4s with 4 ground electrodes seem to require. After initial installation in my yellow 2.5L, the engine "seemed" to start better and idle smoother, but that didn't last a week. It started to require longer crank before first-fire, didn't want to get to a stable idle, and would miss severely between 1500 and 1800 RPM. A cold start required better than 2000 RPM for that initial drive-away or it would flat stall. Those plugs appeared to be gapped at about .060 thousandths, so I lowered the gap to an eyeball .040 thousandths. That didn't help, with less than 3000 miles on these plugs. What made a dramatic difference was replacing them with ACDelco RapidFire #1s gapped to .055-.060 thousandths (not the .045 they come with and tell you not to change). This brought back my hummin-honey with much easier cold starts, a good stable 1600 RPM cold idle, I can let out the throttle without giving it a lot more gas without stalling, takeoff smoothly, with no missing at all, and this is still a cold engine. What difference a $5 a plug can make, even to your wallet. It runs great, feels good, and, furthermore, my mileage has gone back up to the 33-35 MPG (from ~28 mpg). It's fun to drive again! Floyd Dobson

[This message has been edited by X86GT (edited 11-23-2003).]