gingenhagen

Just installed a afr gauge, so now I know what that strange sound is. My idle always does this - every couple of seconds or so, it'll suddenly change pitch for a split second, then go back to normal idling. This corresponds with the afr gauge suddenly reading lean and then jumping back up to normal. Are my injectors misfiring or something? Any ideas on what's wrong?

My engine also always smells of fuel. Don't know if it's related. It's not the FPD, first thing I checked. Haven't done a thorough check for leaks, but I'm planning to replace the fuel hoses.

Kenteth

Hows the RPM during idle?

Technicaly the BAC could be upping the air inject and casuing a higher idle, slightly leaner, and you'll hear both the engine noise change from the rpm difference, and you *might* here the slight change in noise the BAC makes... you've got damn good hearing if you can hear the stepper motor in the BAC though..., especially over the engine noise.

Aaron Cake

iTrader: (1)

The BAC is not a stepper motor. It's a simple solenoid. It has two positions: open and closed. The ECU supplies PWM to the solenoid to vary it's duty cycle.

This is an interesting problem. Sure it's just not an ignition misfire?

Kenteth

^^Ahh, thanks Aaron. I always thought it was a stepper motor for some reason. Is it just the duty cycle on/off frequency that controls the amount of air injection then?

Aaron Cake

iTrader: (1)

Yes. Exactly like a fuel injector.

Travelintrevor

an AFR gauge (the one with the three diff lights) reads lean when you rev and get off the gas ..go try it and tell me if I am right...I sold my AFR a long time ago so I am just going by memory...what you could be describing is a miss..could be a vac leak, bad plugs, bad wires..etc...and your engine should not smell like fuel...unless you have a bad exhaust leak and your ignition system(plugs, wires, coils,etc) is not burning the fuel that is being injected-hence the smell and miss-or "pitch"

gingenhagen

That seems to be a lot of stuff that might be wrong with the car, haha. Would buying a CDI help maybe? The spark plugs are pretty new.

What exactly do you mean by exhaust leak? Like the cat isn't connected correctly to the cat-back? The smell comes from the driver's side anyways. Also, if the fuel wasn't being burned, shouldn't it read rich then? I dunno how a afr gauge works, just that it's hooked up to the o2 sensor and how it's a step function voltage output.

I have no idea what an ignition misfire is or how I'd be able to tell or fix it. Time for some searching and reading.

I'd try that rev thing, 'cept my right arm's kind of in a sling thanks to my bro's poor driving. Heading back to school anyways. If I found a digital video camera somewhere to record the idle, might that help you guys? Thanks a lot for all the help.

edit:
The idle's right around 750. But then with these bursts of lean, it'll drop to 700 then back to 750. When it's warmin up, the idles high from the AWS, I guess, and it's like 1500-2000. The afr gauge reads lean, then slowly goes up to normal as the car warms up. But then again, I've only run the car once with the afr gauge, just revving it in place. Don't think the afr reading changed with revving, but i'm not sure.

gildardo

Is the O2 censor still connected to the ECU. My car does the same thing, the droping idle and goin back up againg, but it doesnt missfire anymore. When the engine misfires it shakes the whole car, so are you sure it's missfirering. Also when worming up my wideband AFR gauge reads rich like 13.5 AFR, but onece it worms up 14.7. I solved the missfire that my car had at low apm with 10mm ignition wires and new spark plugs.

I think that redoing the electric grounding spots might help with the idle rpm dip, I duno.


Gil

gingenhagen

I've redone all my grounds. I don't think it's misfiring, then, 'cause there isn't a violent shaking, just a drop in rpm and change in pitch. If it wasn't for the afr gauge, I'd have no idea it was going lean. I'm just concerned because I've read lean is very bad for the engine. I don't have a wideband (unless the last guy installed one, which i highly doubt). But then I'm confused about why the afr gauge slowly increases. Shouldn't it just have 3 readings - lean normal, rich?

gildardo

You have the non narow band AFR meter. On the narrow band normail is 14.7, for wich the engine control module aims for while crusing. Above and below are the rich and lean, not verry precise, it yust gives you a clue. On mine when all the lights are on and i step on the brakes, the idle drops, so I don't know.


gil