Okay i just installed a new Megasquirt on my car.

I came here to ask some typical car questions i know nothing about. What are some main reasons why i car wont idle. I know one is fuel, the other is spark. I know i have spark, but my afr gauge is reading at 22.0. I know that really lean, buti have the fuel setting up pretty high already. when i lowered the fuel table it ran a way lower afr read out but it was wanting to completely die.

I know this isnt the place for megasquirt question, all I want is some ideas as to why a car wont run. Will a bad IAC reading cause it to not stay on?

 

That's so lean it shouldn't be able to run. Stoichiometric is about 14.7:1 (air to fuel), so your O2 sensor is telling you that you have only 2/3 as fuel as you should.

I'm not sure about MegaSquirt's "high" and "low" fuel settings; i.e. if "high" = a higher injector constant so that it shortens the pulse, or what. But leaving that aside, you need to do 2 things:

1. Make sure your O2 sensor reading is accurate (pretty hard to accomplish ANYTHING if your test eqpt is lying); and

2. Get your fuel up to the point that the A/F ratio comes dwn to the 14:1 - 15:1 range.

When the A/F gauge is showing about 15:1, what does the car run like?

 

Well thats the weird thing. Somehow i got into the afr tables and they were reading 14.5 to 15.5 at around 2k rpm. But the gauge that is on the car and on my megatune software was like it was maxed out.

I am going to pull off my spark plugs today andsee what they are like.

What i really need to knw is what will make a car not idle and just stall out?

Too much gas? too little. What are some theories

 

Too little, usually.

Too little will cause it to lope excessively, have a hard time accelerating off idle when the throttle is snapped open, and tend to slowly kind of die off as it sits idling for a few seconds. It will have EXTREME trouble idling in gear, if it's an auto; and will be easy to kill by cranking the steering wheel (power steering load on the engine) while idling in gear.

Too much will give you that burn-your-eyes / stinky / loaded-up effect that you often see; the "cam lope" will mostly go away, and the exhaust will be a loud puffy drone; what cam lope there is won't sound "crisp", it will just sound sort of rough. You may get smoke, which may be whitish or grayish (from oil), or black.

Make sure your AFR gauge is accurate. I cannot stress this enough. And by this I mean not only that it's a "good" brand and all that, but that it's installed properly, in a place that's representative of the ENTIRE exhaust stream (not high in a collector right immediately behind ONE cyl's primary tube, for example), the heater circuit is working right, and above all, that there aren't things going on that "confuse" its reading.

One problem that's hard to wrap your brain around at first, is that the AFR gauge is NOT measuring FUEL, and it's NOT measuring combustion products; it's measuring OXYGEN. Meaning, if there's oxygen that isn't part of a conbustion reaction in the exhaust stream FOR ANY REASON, then the O2 sensor will pick it up, and the AFR gauge will interpret it as a higher AFR than reality. This means, in order for its indication to be reliable, there must be ABSOLUTELY NO exhaust leaks WHATSOEVER, and NO cylinder misfires WHATSOEVER. Both of these things will put "extra" oxygen into the exhaust and fool the gauge this way. IOW you can take a sick motor with one cyl a dead miss, and set it up to where it's PIG-RICH, and the AFR gauge will STILL say it's lean, because IT SEES THE OXYGEN from the unburned cyl charge.

There's no need for "theories" in this sort of thing. Resist the temptation to treat it as a mystery and beyond complete understanding. It's just a car. We, as a species, pretty much know all there is to know about how they work. they're REAL SIMPLE. If you try to put too much mysticism and "theory" into it instead of hard reality and observations and understanding, you will not succeed.

 

Alright. Im goin to try and recalibrate the 02 sensor. I have an lc-1 from innovate technology. I was curious also as to if my car would run if one of the injectors wasnt running. Could that be possible if i have 4 of them wired to one of the banks and the other 4 to the other bank. They are fairly new injectors and I know they ran before. I was just curious if anything like that could happen. Ehh prolly not im just worrying too much.

 

Air/Fuel Ratio Limits


Try these for a "guide line" after you get calibrated.

All 8 of the injectors Fire (spray) at the same time, once every 4 distributor pulses (double fire).