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Well I took my emissions test today. The target for hydrocarbons at idle is 220, I hit 658

I passed all the other tests flawlessly, except for that. Therefore, I'm ruling out a catalytic converter problem. My idle hasn't been the greatest for a few months now. When I drive around and come to a stop the idle is fine - rock solid at about 800 RPM. After sitting at a stop for about 20 to 30 seconds, the idle begins to 'bounce' between 500 and 750 RPM.

I've reworked the intake system pre-throttle body, so I can rule out any vacuum leaks before then. I cleaned my IAC valve, but does anyone have a way to check this using an ohm-meter?

Anyone have any other thoughts or ideas why my idle does this? And would everyone agree that the reason my car dumping fuel at idle is a cause of my rough idle?

Thanks in advance for your help guys.

I had a similar failure of the idle test, but not the cruise test. I'm betting it was due to using 440cc injectors with the stock ECU. I'll see how it does with the stock ones.

I'm dealing with the same problem. to rich at idle

I was thinking it was the 440s causing the problem, but I'm also running the Revtronix chip. Mike at Revtronix said that the injectors have been scaled back at idle to allow for proper idle.

Do you know anyone with a wideband so you can check your idle?

I have a wideband. It's actually running lean at idle - around 17.3:1. Kind of scary. The Revtronix chip is designed for the AFR target at idle to be the same as at cruise (so around 14.7).

What are your thoughts?

That's kinda wierd. You don't have it after your cat, do you?

When they tested it was your idle bouncing? What does the wideband say when that is going on?


Idle can be tricky to tune sometimes.

I don't have a cat, so yes, it's before the cat. Lol.

It was bouncing when they tested it and when that happens the idle goes extremely lean. As in my wideband reads up to 18.0:1 and when it starts bouncing, the wideband reads "-----" haha.

Can you put a cat on for the test? The main point of a cat is to reduce hydrocarbon emissions.

Yes, I could. The thing is, I'd rather fix the problem rather than the symptom. I know plenty of people in my area that have passed emissions without cats before, so it can be done. Plus, I'm three times over the limit, so I'm not sure if a cat would be able to scale it back enough.

Ah problem found! Car starts idling shitty, unplug MAF, car idles PERFECTLY (although you can't drive it). I've already cleaned it, so I'm assuming it's a dead sensor unless of course other people with the Revtronix chip are having this same problem.

I had bouncing idle issues with my revtronix stage 2 chip while it was still learning fuel trims. Took several hundred miles of driving for it to fix itself. Also air leaks (once again happened to me) can cause the bouncing idle. I got emissions on the car when it was stock this year, so I haven't had to try and pass the sniffer test yet with the chip...

Well, I passed the test today, but that's because I removed the Revtronix chip. Ugh.

I've had the chip in for about 3 weeks now. I'd think that would be enough time for the chip to learn all that it was going to learn. It's almost like there was a problem with the fuel trim at idle. As in maybe the chip had been scaled for 550cc injectors or something.

What injectors are you running BSOD?

I'm running the 'small' 440cc. I've had a wideband installed when the car was stock, so have been able to monitor how things have changed over time. I do recall that it was honestly a good 500+ miles before the ECU completely learned the fuel trims -- AFR during WOT finally raised to 11.5 by then.

Have you fired up RevScan (new version released Friday!) to check the various parameters? The new one has additional fields for various fuel trims, etc. Take a look. Unfortunately, I can't compare to my car right now since it has issues and the ECU is back to an unlearned state.

I'm also running 440cc injectors. My AFR at WOT is at about 12.0:1. A little leaner than I would like, to be honest, but it's still within a tolerable range. The real problem is the shit idle lol. I can't figure it out. I redid a bunch of my intake piping and made sure it was all air-tight, so I'm not worried about leaks.

check my post on the revtronix site i replied to your thread


in short my car was doing EXACTLY what you're describing, after stopping rock solid at 800 or so rpm and then dropping and becoming very bouncy fomr 500 or less rpm up to 750 and back down etc...

my narrowband was off the gauge lean and not cycling at all just staying burried in the lean end meaning there was so much air in the intake that the em couldnt add anymore fuel the trims had already maxed out.

i traced this down to a intake manifold gasket leak.
replaced the gaskets on the weekend and right on the first startup idle rock solid around 650 rpm and o2 cycling perfectly rich to lean to rich to lean like its supposed to...

-Alex

intake manifold gasket or the throttle body to intake manifold gasket? I have read a few threads with tb to the manifold gasket leaking.

Well, I found a leak at the intake manifold to head gasket. It doesn't seem like it's a HUGE leak, but it's definitely there. So looks like I'll be repairing it tomorrow. Anyone know about how long it takes to do?

Well you need to remove the entire manifold I would think, or am I wrong? Did you notice a slight studder without the chip still in your idle? I am wondering if I have the same problem now!

The idle is just as rough as it was with the chip, the only difference is that the AFR at idle is right around 14.7:1 now.

Maybe you could try retorquing the bolts and hopefully it will seal.

Hmmm good thought. Although, the gaskets are almost 20 years old, couldn't hurt to just bite the bullet and do 'em.

Just be careful with the TB and IAC coolant lines. They can be annoying.

Will do! Thanks for the tip, I didn't realize that there was a coolant line on the IAC valve, too.

booyaah told you exact same issue i had. and yeah take the entire manifold off there will be a lot of gunk around the gasket that if not cleaned up could cause issues. and if you can, change the t.b and iac gaskets at the same time, i didnt have them on hand but they both would have been 5 minute jobs with the manifold off.

this is a thread i made about my intake removal, havent put the pics up yet and i really dont have many anyways but i'll try n do it tonight. took me bit under 4 hours to do including sticking a new intercooler in so it really wasnt as big a job as i had thought it would be.
http://bbs.legacycentral.org/viewtopic.php?t=41268

-Alex